information for thread to allow calcru1() (re)use.
Rename ruxagg()->ruxagg_locked(), ruxagg_tlock()->ruxagg() [1].
The ruxagg_locked() function no longer clears thread ticks nor
td_incruntime.
Requested by: attilio [1]
Discussed with: attilio, bde
Reviewed by: bde
Based on submission by: Alexander Krizhanovsky <ak natsys-lab com>
MFC after: 1 week
X-MFC-Note: td_rux shall be moved to the end of struct thread
Remove the altkstacks, instead instantiate threads with kernel stack
allocated with the right size from the start. For the thread that has
kernel stack cached, verify that requested stack size is equial to the
actual, and reallocate the stack if sizes differ [1].
This fixes the bug introduced by r173361 that was committed several days
after r173004 and consisted of kthread_add(9) ignoring the non-default
kernel stack size.
Also, r173361 removed the caching of the kernel stacks for a non-first
thread in the process. Introduce separate kernel stack cache that keeps
some limited amount of preallocated kernel stacks to lower the latency
of thread allocation. Add vm_lowmem handler to prune the cache on
low memory condition. This way, system with reasonable amount of the
threads get lower latency of thread creation, while still not exhausting
significant portion of KVA for unused kstacks.
Submitted by: peter [1]
Discussed with: jhb, julian, peter
Reviewed by: jhb
Tested by: pho (and retested according to new test scenarious)
MFC after: 1 week
allocated with the right size from the start. For the thread that has
kernel stack cached, verify that requested stack size is equial to the
actual, and reallocate the stack if sizes differ [1].
This fixes the bug introduced by r173361 that was committed several days
after r173004 and consisted of kthread_add(9) ignoring the non-default
kernel stack size.
Also, r173361 removed the caching of the kernel stacks for a non-first
thread in the process. Introduce separate kernel stack cache that keeps
some limited amount of preallocated kernel stacks to lower the latency
of thread allocation. Add vm_lowmem handler to prune the cache on
low memory condition. This way, system with reasonable amount of the
threads get lower latency of thread creation, while still not exhausting
significant portion of KVA for unused kstacks.
Submitted by: peter [1]
Discussed with: jhb, julian, peter
Reviewed by: jhb
Tested by: pho
MFC after: 1 week
PCATCH, to indicate that thread shall not be stopped upon receipt of
SIGSTOP until it reaches the kernel->usermode boundary.
Also change thread_single(SINGLE_NO_EXIT) to only stop threads at
the user boundary unconditionally.
Tested by: pho
Reviewed by: jhb
Approved by: re (kensmith)
process that still need to be suspended or exited from thread_single
into the new function calc_remaining().
Tested by: pho
Reviewed by: jhb
Approved by: re (kensmith)
guarantee that all cpus have acknowledged the cleared enable int by
scheduling the resetting thread on each cpu in succession. Since all
lock profiling happens within a critical section this guarantees that
all cpus have left lock profiling before we clear the datastructures.
- Assert that the per-thread queue of locks lock profiling is aware of
is clear on thread exit. There were several cases where this was not
true that slows lock profiling and leaks information.
- Remove all objects from all lists before clearing any per-cpu
information in reset. Lock profiling objects can migrate between
per-cpu caches and previously these migrated objects could be zero'd
before they'd been removed
Discussed with: attilio
Sponsored by: Nokia
This bring huge amount of changes, I'll enumerate only user-visible changes:
- Delegated Administration
Allows regular users to perform ZFS operations, like file system
creation, snapshot creation, etc.
- L2ARC
Level 2 cache for ZFS - allows to use additional disks for cache.
Huge performance improvements mostly for random read of mostly
static content.
- slog
Allow to use additional disks for ZFS Intent Log to speed up
operations like fsync(2).
- vfs.zfs.super_owner
Allows regular users to perform privileged operations on files stored
on ZFS file systems owned by him. Very careful with this one.
- chflags(2)
Not all the flags are supported. This still needs work.
- ZFSBoot
Support to boot off of ZFS pool. Not finished, AFAIK.
Submitted by: dfr
- Snapshot properties
- New failure modes
Before if write requested failed, system paniced. Now one
can select from one of three failure modes:
- panic - panic on write error
- wait - wait for disk to reappear
- continue - serve read requests if possible, block write requests
- Refquota, refreservation properties
Just quota and reservation properties, but don't count space consumed
by children file systems, clones and snapshots.
- Sparse volumes
ZVOLs that don't reserve space in the pool.
- External attributes
Compatible with extattr(2).
- NFSv4-ACLs
Not sure about the status, might not be complete yet.
Submitted by: trasz
- Creation-time properties
- Regression tests for zpool(8) command.
Obtained from: OpenSolaris
unnecessary, the normal process lock and thread lock are enough. The
spin lock is still needed for process and thread exiting to mimic
single sched_lock.
this eliminates some problems of locking, e.g, a thread lock is needed
but can not be used at that time. Only the process lock is needed now
for new field.
thread_unsuspend_one() needs to optionally wakeup the swapper. Since we
hold the thread lock for that entire function, however, we have to push
that requirement up into the caller.
Found by: rwatson
- Speedup the lock orderings lookup modifying the witness graph from a
linked tree to a matrix. A table lookup caches the lock orderings in
order to make a O(1) access for them. Any witness object has an unique
index withing this lookup cache table.
- Reduce the lock contention on w_mtx acquiring it only when the LOR
actually happens and not in a sane case. In order to do this don't totally
flush lock lists (per-CPU spinlocks list and per-thread sleeplocks list)
but check for ll_count anytime we need to have to verify allocations sanity.
- Introduce the function witness_thread_exit() in the witness namespace which
should verify a thread doesn't hold any witness occurrence why exiting.
- Rename the sysctl debug.witness.graphs into debug.witness.fullgraph and
add debug.witness.badstacks which prints out stacks for LOR revealed.
This is implemented using the stack(9) support, which makes WITNESS to be
dependent by the STACK option or by the DDB (including STACK) option.
- Fix style(9) for src/sys/kern/subr_witness.c
The hash table approach has been developed by Ilya Maykov on the behalf of
Isilon Systems which kindly released the patch.
Jeff Roberson, ported the patch to -CURRENT and fixed w_mtx contention, on the
behalf of Nokia.
Submitted by: Ilya Maykov <ivmaykov at gmail dot com> (Isilon Systems), jeff
Sponsored by: Nokia
routine wakes up proc0 so that proc0 can swap the thread back in.
Historically, this has been done by waking up proc0 directly from
setrunnable() itself via a wakeup(). When waking up a sleeping thread
that was swapped out (the usual case when waking proc0 since only sleeping
threads are eligible to be swapped out), this resulted in a bit of
recursion (e.g. wakeup() -> setrunnable() -> wakeup()).
With sleep queues having separate locks in 6.x and later, this caused a
spin lock LOR (sleepq lock -> sched_lock/thread lock -> sleepq lock).
An attempt was made to fix this in 7.0 by making the proc0 wakeup use
the ithread mechanism for doing the wakeup. However, this required
grabbing proc0's thread lock to perform the wakeup. If proc0 was asleep
elsewhere in the kernel (e.g. waiting for disk I/O), then this degenerated
into the same LOR since the thread lock would be some other sleepq lock.
Fix this by deferring the wakeup of the swapper until after the sleepq
lock held by the upper layer has been locked. The setrunnable() routine
now returns a boolean value to indicate whether or not proc0 needs to be
woken up. The end result is that consumers of the sleepq API such as
*sleep/wakeup, condition variables, sx locks, and lockmgr, have to wakeup
proc0 if they get a non-zero return value from sleepq_abort(),
sleepq_broadcast(), or sleepq_signal().
Discussed with: jeff
Glanced at by: sam
Tested by: Jurgen Weber jurgen - ish com au
MFC after: 2 weeks
variables and sysctl nodes.
- In reset walk the children of kern_sched_stats and reset the counters
via the oid_arg1 pointer. This allows us to add arbitrary counters to
the tree and still reset them properly.
- Define a set of switch types to be passed with flags to mi_switch().
These types are named SWT_*. These types correspond to SCHED_STATS
counters and are automatically handled in this way.
- Make the new SWT_ types more specific than the older switch stats.
There are now stats for idle switches, remote idle wakeups, remote
preemption ithreads idling, etc.
- Add switch statistics for ULE's pickcpu algorithm. These stats include
how much migration there is, how often affinity was successful, how
often threads were migrated to the local cpu on wakeup, etc.
Sponsored by: Nokia
to enter thread_suspend_check().
- Set TDF_ASTPENDING along with TDF_NEEDSUSPCHK so we can move the
thread_suspend_check() to ast() rather than userret().
- Check TDF_NEEDSUSPCHK in the sleepq_catch_signals() optimization so
that we don't miss a suspend request. If this is set use the
expensive signal path.
- Set NEEDSUSPCHK when creating a new thread in thr in case the
creating thread is due to be suspended as well but has not yet.
Reviewed by: davidxu (Authored original patch)
thread_fini(). The schedulers initialize themselves properly during
sched_fork_thread() anyhow. fini is only called when we're returning
the memory to the allocator which surely doesn't care what state the
memory is in.
requiring the per-process spinlock to only requiring the process lock.
- Reflect these changes in the proc.h documentation and consumers throughout
the kernel. This is a substantial reduction in locking cost for these
fields and was made possible by recent changes to threading support.
While the KSE project was quite successful in bringing threading to
FreeBSD, the M:N approach taken by the kse library was never developed
to its full potential. Backwards compatibility will be provided via
libmap.conf for dynamically linked binaries and static binaries will
be broken.
sched_sleep(). This removes extra thread_lock() acquisition and
allows the scheduler to decide what to do with the static boost.
- Change the priority arguments to cv_* to match sleepq/msleep/etc.
where 0 means no priority change. Catch -1 in cv_broadcastpri() and
convert it to 0 for now.
- Set a flag when sleeping in a way that is compatible with swapping
since direct priority comparisons are meaningless now.
- Add a sysctl to ule, kern.sched.static_boost, that defaults to on which
controls the boost behavior. Turning it off gives better performance
in some workloads but needs more investigation.
- While we're modifying sleepq, change signal and broadcast to both
return with the lock held as the lock was held on enter.
Reviewed by: jhb, peter
and assignment.
- Add a reference to a struct cpuset in each thread that is inherited from
the thread that created it.
- Release the reference when the thread is destroyed.
- Add prototypes for syscalls and macros for manipulating cpusets in
sys/cpuset.h
- Add syscalls to create, get, and set new numbered cpusets:
cpuset(), cpuset_{get,set}id()
- Add syscalls for getting and setting affinity masks for cpusets or
individual threads: cpuid_{get,set}affinity()
- Add types for the 'level' and 'which' parameters for the cpuset. This
will permit expansion of the api to cover cpu masks for other objects
identifiable with an id_t integer. For example, IRQs and Jails may be
coming soon.
- The root set 0 contains all valid cpus. All thread initially belong to
cpuset 1. This permits migrating all threads off of certain cpus to
reserve them for special applications.
Sponsored by: Nokia
Discussed with: arch, rwatson, brooks, davidxu, deischen
Reviewed by: antoine
details from consumers.
- Track individual selecters on a per-descriptor basis such that there
are no longer collisions and after sleeping for events only those
descriptors which triggered events must be rescaned.
- Protect the selinfo (per descriptor) structure with a mtx pool mutex.
mtx pool mutexes were chosen to preserve api compatibility with
existing code which does nothing but bzero() to setup selinfo
structures.
- Use a per-thread wait channel rather than a global wait channel.
- Hide select implementation details in a seltd structure which is
opaque to the rest of the kernel.
- Provide a 'selsocket' interface for those kernel consumers who wish to
select on a socket when they have no fd so they no longer have to
be aware of select implementation details.
Tested by: kris
Reviewed on: arch
the ABI when enabled. There is no longer an embedded lock_profile_object
in each lock. Instead a list of lock_profile_objects is kept per-thread
for each lock it may own. The cnt_hold statistic is now always 0 to
facilitate this.
- Support shared locking by tracking individual lock instances and
statistics in the per-thread per-instance lock_profile_object.
- Make the lock profiling hash table a per-cpu singly linked list with a
per-cpu static lock_prof allocator. This removes the need for an array
of spinlocks and reduces cache contention between cores.
- Use a seperate hash for spinlocks and other locks so that only a
critical_enter() is required and not a spinlock_enter() to modify the
per-cpu tables.
- Count time spent spinning in the lock statistics.
- Remove the LOCK_PROFILE_SHARED option as it is always supported now.
- Specifically drop and release the scheduler locks in both schedulers
since we track owners now.
In collaboration with: Kip Macy
Sponsored by: Nokia
process_fini, thread_ctor, thread_dtor, thread_init, thread_fini. This
will allow us to extend dynamically areas in proc/thread for dtrace ;-)
Reviewed by: rwatson
communicate that it relates to (is called by) thread_alloc()
o Add cpu_thread_free() which is called from thread_free()
to counter-act cpu_thread_alloc().
i386: Have cpu_thread_free() call cpu_thread_clean() to
preserve behaviour.
ia64: Have cpu_thread_free() call mtx_destroy() for the
mutex initialized in cpu_thread_alloc().
PR: ia64/118024
silent NULL pointer dereference in the i386 and sparc64 pmap_pinit()
when the kmem_alloc_nofault() failed to allocate address space. Both
functions now return error instead of panicing or dereferencing NULL.
As consequence, vmspace_exec() and vmspace_unshare() returns the errno
int. struct vmspace arg was added to vm_forkproc() to avoid dealing
with failed allocation when most of the fork1() job is already done.
The kernel stack for the thread is now set up in the thread_alloc(),
that itself may return NULL. Also, allocation of the first process
thread is performed in the fork1() to properly deal with stack
allocation failure. proc_linkup() is separated into proc_linkup()
called from fork1(), and proc_linkup0(), that is used to set up the
kernel process (was known as swapper).
In collaboration with: Peter Holm
Reviewed by: jhb
kthread_add() takes the same parameters as the old kthread_create()
plus a pointer to a process structure, and adds a kernel thread
to that process.
kproc_kthread_add() takes the parameters for kthread_add,
plus a process name and a pointer to a pointer to a process instead of just
a pointer, and if the proc * is NULL, it creates the process to the
specifications required, before adding the thread to it.
All other old kthread_xxx() calls return, but act on (struct thread *)
instead of (struct proc *). One reason to change the name is so that
any old kernel modules that are lying around and expect kthread_create()
to make a process will not just accidentally link.
fix top to show kernel threads by their thread name in -SH mode
add a tdnam formatting option to ps to show thread names.
make all idle threads actual kthreads and put them into their own idled process.
make all interrupt threads kthreads and put them in an interd process
(mainly for aesthetic and accounting reasons)
rename proc 0 to be 'kernel' and it's swapper thread is now 'swapper'
man page fixes to follow.
In particular:
- smp_tlb_mtx is no longer used, so it is axed.
- smp rendezvous lock isn't really a leaf spin-mutex. Its bad placement in
the table, however, has been the source of a false positive LOR reporting
with the dt_lock. However, smp rendezvous lock would have had sched_lock
there for older lock, so it wasn't still a leaf lock.
- allpmaps is only used in ia32 architecture, so it is inserted in the
appropriate stub.
Addictionally:
- kse_zombie_lock is no longer present, so its definition is axed out.
- zombie_lock doesn't need to have an exported symbol, so just let's it be
declared as static.
Tested by: kris
Approved by: jeff (mentor)
Approved by: re
- p_sflag was mostly protected by PROC_LOCK rather than the PROC_SLOCK or
previously the sched_lock. These bugs have existed for some time.
- Allow swapout to try each thread in a process individually and then
swapin the whole process if any of these fail. This allows us to move
most scheduler related swap flags into td_flags.
- Keep ki_sflag for backwards compat but change all in source tools to
use the new and more correct location of P_INMEM.
Reported by: pho
Reviewed by: attilio, kib
Approved by: re (kensmith)
should call uma_zfree() with various spinlock helds. Rearranging the
code would not help here because we cannot break atomicity respect
prcess spinlock, so the only one choice we have is to defer the operation.
In order to do this use a global queue synchronized through the kse_lock
spinlock which is freed at any thread_alloc() / thread_wait() through a
call to thread_reap().
Note that this approach is not ideal as we should want a per-process
list of zombie upcalls, but it follows initial guidelines of KSE authors.
Tested by: jkim, pav
Approved by: jeff, julian
Approved by: re
dangerous races.
Fix this problems adding correct locking for the members of 'struct
kse_upcall' and other struct proc/struct thread related members.
For the moment, just leave ku_mflag and ku_flags "lazy" locked.
While here, cleanup the code removing the function kse_GC() (unused),
and merging upcall_link(), upcall_unlink(), upcall_stash() in their
respective callers (static functions, very short and only called in one
place).
Reported by: pav
Tested by: pav (on some pointyhat cluster nodes)
Approved by: jeff
Approved by: re
Sponsorized by: NGX Italy (http://www.ngx.it)
- Remove unused kse fields from struct proc.
- Group remaining fields and #ifdef KSE them.
- Move some kern_kse.c only prototypes out of proc and into kern_kse.
Discussed with: Julian
- Add a count of exiting threads, p_exitthreads, to struct proc.
- Increment p_exithreads when we set the deadthread in thread_exit().
- When we thread_stash() a deadthread use an atomic to drop the count.
- Spin until the p_exithreads count reaches 0 in thread_wait().
- Lock the last exiting thread momentarily to be certain that it has
exited cpu_throw().
- Restructure thread_wait(). It does not need a loop as there will only
ever be one thread.
Tested by: moose@opera.com
Reported by: kris, moose@opera.com
- Unsafeness on ruadd() in thread_exit()
- Unatomicity of thread_exiit() in the exit1() operations
This patch addresses these problems allocating p_fd as part of the
process and modifying the way it is accessed.
A small chunk of this patch, resolves a race about p_state in kern_wait(),
since we have to be sure about the zombif-ing process.
Submitted by: jeff
Approved by: jeff (mentor)
- Use thread_lock() rather than sched_lock for per-thread scheduling
sychronization.
- Use the per-process spinlock rather than the sched_lock for per-process
scheduling synchronization.
- Move some common code into thread_suspend_switch() to handle the
mechanics of suspending a thread. The locking here is incredibly
convoluted and should be simplified.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
Now, we assume no more sched_lock protection for some of them and use the
distribuited loads method for vmmeter (distribuited through CPUs).
Reviewed by: alc, bde
Approved by: jeff (mentor)
td_ru. This removes the requirement for per-process synchronization in
statclock() and mi_switch(). This was previously supported by
sched_lock which is going away. All modifications to rusage are now
done in the context of the owning thread. reads proceed without locks.
- Aggregate exiting threads rusage in thread_exit() such that the exiting
thread's rusage is not lost.
- Provide a new routine, rufetch() to fetch an aggregate of all rusage
structures from all threads in a process. This routine must be used
in any place requiring a rusage from a process prior to it's exit. The
exited process's rusage is still available via p_ru.
- Aggregate tick statistics only on demand via rufetch() or when a thread
exits. Tick statistics are kept in the thread and protected by sched_lock
until it exits.
Initial patch by: attilio
Reviewed by: attilio, bde (some objections), arch (mostly silent)
Probabilly, a general approach is not the better solution here, so we should
solve the sched_lock protection problems separately.
Requested by: alc
Approved by: jeff (mentor)
vmcnts. This can be used to abstract away pcpu details but also changes
to use atomics for all counters now. This means sched lock is no longer
responsible for protecting counts in the switch routines.
Contributed by: Attilio Rao <attilio@FreeBSD.org>
always 0. Previously we aligned threads on a minimum of 8-byte boundaries.
Note: This changes the uma zone to no longer cache align threads. We
really want the uma zone to do align threads to MAX(16, cache line size)
but there currently isn't a good way to express that to uma.
Submitted by: attilio
GETATTRs being generated - one from lookup()/namei() and the other
from nfs_open() (for cto consistency). This change eliminates the
GETATTR in nfs_open() if an otw GETATTR was done from the namei()
path. Instead of extending the vop interface, we timestamp each attr
load, and use this to detect whether a GETATTR was done from namei()
for this syscall. Introduces a thread-local variable that counts the
syscalls made by the thread and uses <pid, tid, thread syscalls> as
the attrload timestamp. Thanks to jhb@ and peter@ for a discussion on
thread state that could be used as the timestamp with minimal overhead.
Make part of John Birrell's KSE patch permanent..
Specifically, remove:
Any reference of the ksegrp structure. This feature was
never fully utilised and made things overly complicated.
All code in the scheduler that tried to make threaded programs
fair to unthreaded programs. Libpthread processes will already
do this to some extent and libthr processes already disable it.
Also:
Since this makes such a big change to the scheduler(s), take the opportunity
to rename some structures and elements that had to be moved anyhow.
This makes the code a lot more readable.
The ULE scheduler compiles again but I have no idea if it works.
The 4bsd scheduler still reqires a little cleaning and some functions that now do
ALMOST nothing will go away, but I thought I'd do that as a separate commit.
Tested by David Xu, and Dan Eischen using libthr and libpthread.
mutex structure is added as following:
struct umutex {
__lwpid_t m_owner;
uint32_t m_flags;
uint32_t m_ceilings[2];
uint32_t m_spare[4];
};
The m_owner represents owner thread, it is a thread id, in non-contested
case, userland can simply use atomic_cmpset_int to lock the mutex, if the
mutex is contested, high order bit will be set, and userland should do locking
and unlocking via kernel syscall. Flag UMUTEX_PRIO_INHERIT represents
pthread's PTHREAD_PRIO_INHERIT mutex, which when contention happens, kernel
should do priority propagating. Flag UMUTEX_PRIO_PROTECT indicates it is
pthread's PTHREAD_PRIO_PROTECT mutex, userland should initialize m_owner
to contested state UMUTEX_CONTESTED, then atomic_cmpset_int will be failure
and kernel syscall should be invoked to do locking, this becauses
for such a mutex, kernel should always boost the thread's priority before
it can lock the mutex, m_ceilings is used by PTHREAD_PRIO_PROTECT mutex,
the first element is used to boost thread's priority when it locked the mutex,
second element is used when the mutex is unlocked, the PTHREAD_PRIO_PROTECT
mutex's link list is kept in userland, the m_ceiling[1] is managed by thread
library so kernel needn't allocate memory to keep the link list, when such
a mutex is unlocked, kernel reset m_owner to UMUTEX_CONTESTED.
Flag USYNC_PROCESS_SHARED indicate if the synchronization object is process
shared, if the flag is not set, it saves a vm_map_lookup() call.
The umtx chain is still used as a sleep queue, when a thread is blocked on
PTHREAD_PRIO_INHERIT mutex, a umtx_pi is allocated to support priority
propagating, it is dynamically allocated and reference count is used,
it is not optimized but works well in my tests, while the umtx chain has
its own locking protocol, the priority propagating protocol are all protected
by sched_lock because priority propagating function is called with sched_lock
held from scheduler.
No visible performance degradation is found which these changes. Some parameter
names in _umtx_op syscall are renamed.
suspension code. When a thread A is going to sleep, it calls
sleepq_catch_signals() to detect any pending signals or thread
suspension request, if nothing happens, it returns without
holding process lock or scheduler lock, this opens a race
window which allows thread B to come in and do process
suspension work, however since A is still at running state,
thread B can do nothing to A, thread A continues, and puts
itself into actually sleeping state, but B has never seen it,
and it sits there forever until B is woken up by other threads
sometimes later(this can be very long delay or never
happen). Fix this bug by forcing sleepq_catch_signals to
return with scheduler lock held.
Fix sleepq_abort() by passing it an interrupted code, previously,
it worked as wakeup_one(), and the interruption can not be
identified correctly by sleep queue code when the sleeping
thread is resumed.
Let thread_suspend_check() returns EINTR or ERESTART, so sleep
queue no longer has to use SIGSTOP as a hack to build a return
value.
Reviewed by: jhb
MFC after: 1 week
remote CPU. While here, abstract thread suspension code into a function
called sig_suspend_threads, the function is called when a process received
a STOP signal.
audit thread exit, but should that happen, this will prevent
unhappiness, as the thread exit system call will never return, and
hence not commit the record.
Pointed out by/with: cognet
Obtained from: TrustedBSD Project
This should not happen, but with this assert, brueffer and I would
not have spent 45 minutes trying to figure out why he wasn't
seeing audit records with the audit version in CVS.
Obtained from: TrustedBSD Project
- td_ar to struct thread, which holds the in-progress audit record during
a system call.
- p_au to struct proc, which holds per-process audit state, such as the
audit identifier, audit terminal, and process audit masks.
In the earlier implementation, td_ar was added to the zero'd section of
struct thread. In order to facilitate merging to RELENG_6, it has been
moved to the end of the data structure, requiring explicit
initalization in the thread constructor.
Much help from: wsalamon
Obtained from: TrustedBSD Project
For each child process whose status has been changed, a SIGCHLD instance
is queued, if the signal is stilling pending, and process changed status
several times, signal information is updated to reflect latest process
status. If wait() returns because the status of a child process is
available, pending SIGCHLD signal associated with the child process is
discarded. Any other pending SIGCHLD signals remain pending.
The signal information is allocated at the same time when proc structure
is allocated, if process signal queue is fully filled or there is a memory
shortage, it can still send the signal to process.
There is a booting time tunable kern.sigqueue.queue_sigchild which
can control the behavior, setting it to zero disables the SIGCHLD queueing
feature, the tunable will be removed if the function is proved that it is
stable enough.
Tested on: i386 (SMP and UP)
clock are supported. I have plan to merge XSI timer ITIMER_REAL and other
two CPU timers into the new code, current three slots are available for
the XSI timers.
The SIGEV_THREAD notification type is not supported yet because our
sigevent struct lacks of two member fields:
sigev_notify_function
sigev_notify_attributes
I have found the sigevent is used in AIO, so I won't add the two members
unless the AIO code is adjusted.
changes in MD code are trivial, before this change, trapsignal and
sendsig use discrete parameters, now they uses member fields of
ksiginfo_t structure. For sendsig, this change allows us to pass
POSIX realtime signal value to user code.
2. Remove cpu_thread_siginfo, it is no longer needed because we now always
generate ksiginfo_t data and feed it to libpthread.
3. Add p_sigqueue to proc structure to hold shared signals which were
blocked by all threads in the proc.
4. Add td_sigqueue to thread structure to hold all signals delivered to
thread.
5. i386 and amd64 now return POSIX standard si_code, other arches will
be fixed.
6. In this sigqueue implementation, pending signal set is kept as before,
an extra siginfo list holds additional siginfo_t data for signals.
kernel code uses psignal() still behavior as before, it won't be failed
even under memory pressure, only exception is when deleting a signal,
we should call sigqueue_delete to remove signal from sigqueue but
not SIGDELSET. Current there is no kernel code will deliver a signal
with additional data, so kernel should be as stable as before,
a ksiginfo can carry more information, for example, allow signal to
be delivered but throw away siginfo data if memory is not enough.
SIGKILL and SIGSTOP have fast path in sigqueue_add, because they can
not be caught or masked.
The sigqueue() syscall allows user code to queue a signal to target
process, if resource is unavailable, EAGAIN will be returned as
specification said.
Just before thread exits, signal queue memory will be freed by
sigqueue_flush.
Current, all signals are allowed to be queued, not only realtime signals.
Earlier patch reviewed by: jhb, deischen
Tested on: i386, amd64
in other codes. Add cpu_set_user_tls, use it to tweak user register
and setup user TLS. I ever wanted to merge it into cpu_set_kse_upcall,
but since cpu_set_kse_upcall is also used by M:N threads which may
not need this feature, so I wrote a separated cpu_set_user_tls.
all other threads to suicide, problem is execve() could be failed, and
a failed execve() would change threaded process to unthreaded, this side
effect is unexpected.
The new code introduces a new single threading mode SINGLE_BOUNDARY, in
the mode, all threads should suspend themself at user boundary except
the singler. we can not use SINGLE_NO_EXIT because we want to start from
a clean state if execve() is successful, suspending other threads at unknown
point and later resuming them from there and forcing them to exit at user
boundary may cause the process to start from a dirty state. If execve() is
successful, current thread upgrades to SINGLE_EXIT mode and forces other
threads to suicide at user boundary, otherwise, other threads will be resumed
and their interrupted syscall will be restarted.
Reviewed by: julian
but with slightly cleaned up interfaces.
The KSE structure has become the same as the "per thread scheduler
private data" structure. In order to not make the diffs too great
one is #defined as the other at this time.
The KSE (or td_sched) structure is now allocated per thread and has no
allocation code of its own.
Concurrency for a KSEGRP is now kept track of via a simple pair of counters
rather than using KSE structures as tokens.
Since the KSE structure is different in each scheduler, kern_switch.c
is now included at the end of each scheduler. Nothing outside the
scheduler knows the contents of the KSE (aka td_sched) structure.
The fields in the ksegrp structure that are to do with the scheduler's
queueing mechanisms are now moved to the kg_sched structure.
(per ksegrp scheduler private data structure). In other words how the
scheduler queues and keeps track of threads is no-one's business except
the scheduler's. This should allow people to write experimental
schedulers with completely different internal structuring.
A scheduler call sched_set_concurrency(kg, N) has been added that
notifies teh scheduler that no more than N threads from that ksegrp
should be allowed to be on concurrently scheduled. This is also
used to enforce 'fainess' at this time so that a ksegrp with
10000 threads can not swamp a the run queue and force out a process
with 1 thread, since the current code will not set the concurrency above
NCPU, and both schedulers will not allow more than that many
onto the system run queue at a time. Each scheduler should eventualy develop
their own methods to do this now that they are effectively separated.
Rejig libthr's kernel interface to follow the same code paths as
linkse for scope system threads. This has slightly hurt libthr's performance
but I will work to recover as much of it as I can.
Thread exit code has been cleaned up greatly.
exit and exec code now transitions a process back to
'standard non-threaded mode' before taking the next step.
Reviewed by: scottl, peter
MFC after: 1 week
syscall can interrupt other thread's syscall in sleepq_catch_signals().
Current, all callers know thread_suspend_check may suspend thread
itself, so we need't to check return_instead for normal suspension
flags (no P_SINGLE_EXIT set).
Tested by: deischen
Reported by: Maarten L. Hekkelman <m.hekkelman@cmbi.kun.nl>
have been unified with that of msleep(9), further refine the sleepq
interface and consolidate some duplicated code:
- Move the pre-sleep checks for theaded processes into a
thread_sleep_check() function in kern_thread.c.
- Move all handling of TDF_SINTR to be internal to subr_sleepqueue.c.
Specifically, if a thread is awakened by something other than a signal
while checking for signals before going to sleep, clear TDF_SINTR in
sleepq_catch_signals(). This removes a sched_lock lock/unlock combo in
that edge case during an interruptible sleep. Also, fix
sleepq_check_signals() to properly handle the condition if TDF_SINTR is
clear rather than requiring the callers of the sleepq API to notice
this edge case and call a non-_sig variant of sleepq_wait().
- Clarify the flags arguments to sleepq_add(), sleepq_signal() and
sleepq_broadcast() by creating an explicit submask for sleepq types.
Also, add an explicit SLEEPQ_MSLEEP type rather than a magic number of
0. Also, add a SLEEPQ_INTERRUPTIBLE flag for use with sleepq_add() and
move the setting of TDF_SINTR to sleepq_add() if this flag is set rather
than sleepq_catch_signals(). Note that it is the caller's responsibility
to ensure that sleepq_catch_signals() is called if and only if this flag
is passed to the preceeding sleepq_add(). Note that this also removes a
sched_lock lock/unlock pair from sleepq_catch_signals(). It also ensures
that for an interruptible sleep, TDF_SINTR is always set when
TD_ON_SLEEPQ() is true.
so that they know whether the allocation is supposed to be able to sleep
or not.
* Allow uma_zone constructors and initialation functions to return either
success or error. Almost all of the ones in the tree currently return
success unconditionally, but mbuf is a notable exception: the packet
zone constructor wants to be able to fail if it cannot suballocate an
mbuf cluster, and the mbuf allocators want to be able to fail in general
in a MAC kernel if the MAC mbuf initializer fails. This fixes the
panics people are seeing when they run out of memory for mbuf clusters.
* Allow debug.nosleepwithlocks on WITNESS to be disabled, without changing
the default.
Both bmilekic and jeff have reviewed the changes made to make failable
zone allocations work.
specify "us" as the thread not the process/ksegrp/kse.
You can always find the others from the thread but the converse is not true.
Theorotically this would lead to runtime being allocated to the wrong
entity in some cases though it is not clear how often this actually happenned.
(would only affect threaded processes and would probably be pretty benign,
but it WAS a bug..)
Reviewed by: peter
1. Add tm_lwpid into kse_thr_mailbox to indicate which kernel
thread current user thread is running on. Add tm_dflags into
kse_thr_mailbox, the flags is written by debugger, it tells
UTS and kernel what should be done when the process is being
debugged, current, there two flags TMDF_SSTEP and TMDF_DONOTRUNUSER.
TMDF_SSTEP is used to tell kernel to turn on single stepping,
or turn off if it is not set.
TMDF_DONOTRUNUSER is used to tell kernel to schedule upcall
whenever possible, to UTS, it means do not run the user thread
until debugger clears it, this behaviour is necessary because
gdb wants to resume only one thread when the thread's pc is
at a breakpoint, and thread needs to go forward, in order to
avoid other threads sneak pass the breakpoints, it needs to remove
breakpoint, only wants one thread to go. Also, add km_lwp to
kse_mailbox, the lwp id is copied to kse_thr_mailbox at context
switch time when process is not being debugged, so when process
is attached, debugger can map kernel thread to user thread.
2. Add p_xthread to proc strcuture and td_xsig to thread structure.
p_xthread is used by a thread when it wants to report event
to debugger, every thread can set the pointer, especially, when
it is used in ptracestop, it is the last thread reporting event
will win the race. Every thread has a td_xsig to exchange signal
with debugger, thread uses TDF_XSIG flag to indicate it is reporting
signal to debugger, if the flag is not cleared, thread will keep
retrying until it is cleared by debugger, p_xthread may be
used by debugger to indicate CURRENT thread. The p_xstat is still
in proc structure to keep wait() to work, in future, we may
just use td_xsig.
3. Add TDF_DBSUSPEND flag, the flag is used by debugger to suspend
a thread. When process stops, debugger can set the flag for
thread, thread will check the flag in thread_suspend_check,
enters a loop, unless it is cleared by debugger, process is
detached or process is existing. The flag is also checked in
ptracestop, so debugger can temporarily suspend a thread even
if the thread wants to exchange signal.
4. Current, in ptrace, we always resume all threads, but if a thread
has already a TDF_DBSUSPEND flag set by debugger, it won't run.
Encouraged by: marcel, julian, deischen
switch to. If a non-NULL thread pointer is passed in, then the CPU will
switch to that thread directly rather than calling choosethread() to pick
a thread to choose to.
- Make sched_switch() aware of idle threads and know to do
TD_SET_CAN_RUN() instead of sticking them on the run queue rather than
requiring all callers of mi_switch() to know to do this if they can be
called from an idlethread.
- Move constants for arguments to mi_switch() and thread_single() out of
the middle of the function prototypes and up above into their own
section.
The overhead of unconditionally allocating TIDs (and likewise,
unconditionally deallocating them), is amortized across multiple
thread creations by the way UMA makes it possible to have type-stable
storage.
Previously the cost was kept down by having threads created as part
of a fork operation use the process' PID as the TID. While this had
some nice properties, it also introduced complexity in the way TIDs
were allocated. Most importantly, by using the type-stable storage
that UMA gives us this was also unnecessary.
This change affects how core dumps are created and in particular how
the PRSTATUS notes are dumped. Since we don't have a thread with a
TID equalling the PID, we now need a different way to preserve the
old and previous behavior. We do this by having the given thread (i.e.
the thread passed to the core dump code in td) dump it's state first
and fill in pr_pid with the actual PID. All other threads will have
pr_pid contain their TIDs. The upshot of all this is that the debugger
will now likely select the right LWP (=TID) as the initial thread.
Credits to: julian@ for spotting how we can utilize UMA.
Thanks to: all who provided julian@ with test results.
This is not really used by the process but it's confusing to some
status readers to see zombie processes the "runnin" threads.
Pointed out by: Don Lewis <truckman@FreeBSD.org>
of not clearing the flags for execv() syscall will result that a new
program runs in KSE thread mode without enabling it.
Submitted by: tjr
Modified by: davidxu
condition where kse_wakeup() doesn't yet see them in (interruptible)
sleep queues. Also add an upcall check to sleepqueue_catch_signals()
suggested by jhb.
This commit should fix recent mysql hangs.
Reviewed by: jhb, davidxu
Mysql'd by: Robin P. Blanchard <robin.blanchard at gactr uga edu>
is twofold:
1. When a 1:1 or M:N threaded process dumps core, we need to put the
register state of each of its kernel threads in the core file.
This can only be done by differentiating the pid field in the
respective note. For this we need the tid.
2. When thread support is present for remote debugging the kernel
with gdb(1), threads need to be identified by an integer due to
limitations in the remote protocol. This requires having a tid.
To minimize the impact of having thread IDs, threads that are created
as part of a fork (i.e. the initial thread in a process) will inherit
the process ID (i.e. tid=pid). Subsequent threads will have IDs larger
than PID_MAX to avoid interference with the pid allocation algorithm.
The assignment of tids is handled by thread_new_tid().
The thread ID allocation algorithm has been written with 3 assumptions
in mind:
1. IDs need to be created as fast a possible,
2. Reuse of IDs may happen instantaneously,
3. Someone else will write a better algorithm.
- no longer serialize on Giant for thread_single*() and family in fork,
exit and exec
- thread_wait() is mpsafe, assert no Giant
- reduce scope of Giant in exit to not cover thread_wait and just do
vm_waitproc().
- assert that thread_single() family are not called with Giant
- remove the DROP/PICKUP_GIANT macros from thread_single() family
- assert that thread_suspend_check() s not called with Giant
- remove manual drop_giant hack in thread_suspend_check since we know it
isn't held.
- remove the DROP/PICKUP_GIANT macros from thread_suspend_check() family
- mark kse_create() mpsafe
race in between sleepq_add() and sleepq_catch_signals() in that setting
td_wchan and TDF_SINTR is not atomic to sched_lock but only to the sleepq
lock. This band-aid will stop assertion failures, but there is perhaps a
larger problem with the sleepq_add/sleepq_catch_signals race that I am not
sure how to solve. For the signals case the race is harmless because we
always call cursig() after setting TDF_SINTR. However, KSE doesn't do
anything in sleepq_catch_signals() to check that this race was lost, so I
am unsure if this race is harmful for this specific abort.
sleep queue interface:
- Sleep queues attempt to merge some of the benefits of both sleep queues
and condition variables. Having sleep qeueus in a hash table avoids
having to allocate a queue head for each wait channel. Thus, struct cv
has shrunk down to just a single char * pointer now. However, the
hash table does not hold threads directly, but queue heads. This means
that once you have located a queue in the hash bucket, you no longer have
to walk the rest of the hash chain looking for threads. Instead, you have
a list of all the threads sleeping on that wait channel.
- Outside of the sleepq code and the sleep/cv code the kernel no longer
differentiates between cv's and sleep/wakeup. For example, calls to
abortsleep() and cv_abort() are replaced with a call to sleepq_abort().
Thus, the TDF_CVWAITQ flag is removed. Also, calls to unsleep() and
cv_waitq_remove() have been replaced with calls to sleepq_remove().
- The sched_sleep() function no longer accepts a priority argument as
sleep's no longer inherently bump the priority. Instead, this is soley
a propery of msleep() which explicitly calls sched_prio() before
blocking.
- The TDF_ONSLEEPQ flag has been dropped as it was never used. The
associated TDF_SET_ONSLEEPQ and TDF_CLR_ON_SLEEPQ macros have also been
dropped and replaced with a single explicit clearing of td_wchan.
TD_SET_ONSLEEPQ() would really have only made sense if it had taken
the wait channel and message as arguments anyway. Now that that only
happens in one place, a macro would be overkill.
SW_INVOL. Assert that one of these is set in mi_switch() and propery
adjust the rusage statistics. This is to simplify the large number of
users of this interface which were previously all required to adjust the
proper counter prior to calling mi_switch(). This also facilitates more
switch and locking optimizations.
- Change all callers of mi_switch() to pass the appropriate paramter and
remove direct references to the process statistics.
Presumably, at some point, you had to include jail.h if you included
proc.h, but that is no longer required.
Result of: self injury involving adding something to struct prison
to have the kernel switch to a new thread, instead of doing it in
userland. It is in fact needed on ia64 where syscall restarts do not
return to userland first. It's completely handled inside the kernel.
As such, any context created by the kernel as part of an upcall and
caused by some syscall needs to be restored by the kernel.
turnstiles to implement blocking isntead of implementing a thread queue
directly. These turnstiles are somewhat similar to those used in Solaris 7
as described in Solaris Internals but are also different.
Turnstiles do not come out of a fixed-sized pool. Rather, each thread is
assigned a turnstile when it is created that it frees when it is destroyed.
When a thread blocks on a lock, it donates its turnstile to that lock to
serve as queue of blocked threads. The queue associated with a given lock
is found by a lookup in a simple hash table. The turnstile itself is
protected by a lock associated with its entry in the hash table. This
means that sched_lock is no longer needed to contest on a mutex. Instead,
sched_lock is only used when manipulating run queues or thread priorities.
Turnstiles also implement priority propagation inherently.
Currently turnstiles only support mutexes. Eventually, however, turnstiles
may grow two queue's to support a non-sleepable reader/writer lock
implementation. For more details, see the comments in sys/turnstile.h and
kern/subr_turnstile.c.
The two primary advantages from the turnstile code include: 1) the size
of struct mutex shrinks by four pointers as it no longer stores the
thread queue linkages directly, and 2) less contention on sched_lock in
SMP systems including the ability for multiple CPUs to contend on different
locks simultaneously (not that this last detail is necessarily that much of
a big win). Note that 1) means that this commit is a kernel ABI breaker,
so don't mix old modules with a new kernel and vice versa.
Tested on: i386 SMP, sparc64 SMP, alpha SMP
cpu_switch() where both the old and new threads are passed in as
arguments. Only powerpc uses the old conventions now.
- Update comments in the Alpha swtch.s to reflect KSE changes.
Tested by: obrien, marcel
than i386 or AMD64, TP register points to thread mailbox, and they can not
atomically clear km_curthread in kse mailbox, in this case, thread retrieves
its thread pointer from TP register and sets flag TMF_NOUPCALL in its thread
mailbox to indicate a critical region.
be delivered to that thread, regardless of whether it
has it masked or not.
Previously, if the targeted thread had the signal masked,
it would be put on the processes' siglist. If
another thread has the signal umasked or unmasks it before
the target, then the thread it was intended for would never
receive it.
This patch attempts to solve the problem by requiring callers
of tdsignal() to say whether the signal is for the thread or
for the process. If it is for the process, then normal processing
occurs and any thread that has it unmasked can receive it.
But if it is destined for a specific thread, it is put on
that thread's pending list regardless of whether it is currently
masked or not.
The new behaviour still needs more work, though. If the signal
is reposted for some reason it is always posted back to the
thread that handled it because the information regarding the
target of the signal has been lost by then.
Reviewed by: jdp, jeff, bde (style)
happens to work on 32-bit platforms as sizeof(long)=sizeof(int), but
wrecks all kinds of havoc (garbage reads, corrupting writes and
misaligned loads/stores) on 64-bit architectures.
The fix for now is to use fuword32() and suword32() and change the
type of the applicable int fields to int32. This is to make it
explicit that we depend on these fields being 32-bit. We may want
to revisit this later.
Reviewed by: deischen
or unblock a thread in kernel, and allow UTS to specify whether syscall
should be restarted.
o Add ability for UTS to monitor signal comes in and removed from process,
the flag PS_SIGEVENT is used to indicate the events.
o Add a KMF_WAITSIGEVENT for KSE mailbox flag, UTS call kse_release with
this flag set to wait for above signal event.
o For SA based thread, kernel masks all signal in its signal mask, let
UTS to use kse_thr_interrupt interrupt a thread, and install a signal
frame in userland for the thread.
o Add a tm_syncsig in thread mailbox, when a hardware trap occurs,
it is used to deliver synchronous signal to userland, and upcall
is schedule, so UTS can process the synchronous signal for the thread.
Reviewed by: julian (mentor)
before calling it for bound thread. To avoid this problem, change
thread_schedule_upcall to not put new thread on run queue, let caller
do it, so we can tweak the new thread before setting it to run.
Reported by: pho
schedules an upcall. Signal delivering to a bound thread is same as
non-threaded process. This is intended to be used by libpthread to
implement PTHREAD_SCOPE_SYSTEM thread.
2. Simplify kse_release() a bit, remove sleep loop.
