better check for 'adjacent'. The old code assumed that if two resources
were adjacent in the linked list that they were also adjacent range wise.
This is not true when a resource manager has to manage disparate regions.
For example, the current interrupt code on i386/amd64 will instruct
irq_rman to manage two disjoint regions: 0-1 and 3-15 for the non-APIC
case. If IRQs 1 and 3 were allocated and then released, the old code
would coalesce across the 1 to 3 boundary because the resources were
adjacent in the linked list thus adding 2 to the area of resources that
irq_rman managed as a side effect. The fix adds extra checks so that
adjacent unallocated resources are only merged with the resource being
freed if the start and end values of the resources also match up. The
patch also consolidates the checks for adjacent resources being allocated.
spin-wait code to use the same spin mutex (smp_tlb_mtx) as the TLB ipi
and spin-wait code snippets so that you can't get into the situation of
one CPU doing a TLB shootdown to another CPU that is doing a lazy pmap
shootdown each of which are waiting on each other. With this change, only
one of the CPUs would do an IPI and spin-wait at a time.
the immediate awakening of proc0 (scheduler kproc, controls swapping
processes in and out). The scheduler process periodically awakens already,
so this will not result in processes not being swapped in, there will just
be more latency in between a thread being made runnable and the scheduler
waking up to swap the affected process back in.
macros and pass the value to the associated _mtx_*() functions to avoid
more curthread dereferences in the function implementations. This provided
a very modest perf improvement in some benchmarks.
Suggested by: rwatson
Tested by: scottl
a sleep() call waking up in namei(), a later assertion triggers that
Giant is not held. By asserting Giant at the start of namei(), we can
know that if that assertion triggers, Giant is lost during the call to
namei(), and not before.
being defined, define and use a new MD macro, cpu_spinwait(). It only
expands to something on i386 and amd64, so the compiled code should be
identical.
Name of the macro found by: jhb
Reviewed by: jhb
pipelock(), not via a mixture of mutexes and pipelock(). Additionally,
add a few KASSERTS, and change some statements that should have been
KASSERTS into KASSERTS.
As a result of these cleanups, some segments of code have become
significantly shorter and/or easier to read.
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.
and refuse initializing filesystems with a wrong version. This will
aid maintenance activites on the 5-stable branch.
s/vfs_mount/vfs_omount/
s/vfs_nmount/vfs_mount/
Name our filesystems mount function consistently.
Eliminate the namiedata argument to both vfs_mount and vfs_omount.
It was originally there to save stack space. A few places abused
it to get hold of some credentials to pass around. Effectively
it is unused.
Reorganize the root filesystem selection code.
Add local rootvp variables as needed.
Remove checks for miniroot's in the swappartition. We never did that
and most of the filesystems could never be used for that, but it had
still been copy&pasted all over the place.
dereference curthread. It is called only from critical_{enter,exit}(),
which already dereferences curthread. This doesn't seem to affect SMP
performance in my benchmarks, but improves MySQL transaction throughput
by about 1% on UP on my Xeon.
Head nodding: jhb, bmilekic
an adaptive fashion when adaptive mutexes are enabled. The theory
behind non-adaptive Giant is that Giant will be held for long periods
of time, and therefore spinning waiting on it is wasteful. However,
in MySQL benchmarks which are relatively Giant-free, running Giant
adaptive makes an observable difference on SMP (5% transaction rate
improvement). As such, make adaptive behavior on Giant an option so
it can be more widely benchmarked.
- Push down Giant into shmexit(). (Giant is acquired only if the vmspace
contains shm segments.)
- Eliminate the acquisition of Giant from proc_rwmem().
- Reduce the scope of Giant in exit1(), uncovering the destruction of the
address space.
switch in fork_exit() to before anything else is done (but keep
schedlock for the deadthread check). This means one less
nasty bug if ever in the future whatever might have been called
before the update played with schedlock or critical sections.
Discussed with: tjr
the system" resource limit code: When checking if the caller has superuser
privileges, we should be checking the *real* user, not the *effective*
user. (In general, resource limiting is done based on the real user, in
order to avoid resource-exhaustion-by-setuid-program attacks.)
Now that a SUSER_RUID flag to suser_cred exists, use it here to return
this code to its correct behaviour.
Pointed out by: rwatson
somewhat clearer, but more importantly allows for a consistent naming
scheme for suser_cred flags.
The old name is still defined, but will be removed in a few days (unless I
hear any complaints...)
Discussed with: rwatson, scottl
Requested by: jhb
the license from /usr/src/COPYRIGHT. Since cvs annotate shows that
this was written by jasone, julian, jhb, peter, bmilekic and obrien.
cvs log shows that many others may have contributed to this file. As
such, go ahead and use the author of 'FreeBSD Project' for this file.
If this is a problem, please notify me.
# this eliminates the last file in the kernel with an indirect reference
# to /usr/src/COPYRIGHT in the kernel. A few more in userland remain.
can't yet be referenced by other threads.
In microbenchmarks, this appears to reduce the cost of
pipe();close();close() on UP by 10%, and SMP by 7%. The vast majority
of the cost of allocating a pipe remains VM magic.
Suggested by: silby
Giant conditional on debug.mpsafenet in the socket soo_stat() routine,
unconditionally in vn_statfile() for VFS, and otherwise don't acquire
Giant. Accept an unlocked read in kqueue_stat(), and cryptof_stat() is
a no-op. Don't acquire Giant in fstat() system call.
Note: in fdescfs, fo_stat() is called while holding Giant due to the VFS
stack sitting on top, and therefore there will still be Giant recursion
in this case.
individual file object implementations can optionally acquire Giant if
they require it:
- soo_close(): depends on debug.mpsafenet
- pipe_close(): Giant not acquired
- kqueue_close(): Giant required
- vn_close(): Giant required
- cryptof_close(): Giant required (conservative)
Notes:
Giant is still acquired in close() even when closing MPSAFE objects
due to kqueue requiring Giant in the calling closef() code.
Microbenchmarks indicate that this removal of Giant cuts 3%-3% off
of pipe create/destroy pairs from user space with SMP compiled into
the kernel.
The cryptodev and opencrypto code appears MPSAFE, but I'm unable to
test it extensively and so have left Giant over fo_close(). It can
probably be removed given some testing and review.
thread-local pointer, in practice that thread needs to be curthread. If
we're running with INVARIANTS, generate a warning if not. If we have
KDB compiled in, generate a stack trace. This doesn't fire at all in my
local test environment, but could be irritating if it fires frequently
for someone, so there will be motivation to fix things quickly when it
does.
(WITNESS) for code paths that always call uma_zalloc_arg() shortly
after where the check was, because uma_zalloc_arg() already does
a similar check.
No objections from Alfred. Thanks Alfred.
work very infrequently, and often results in a compound panic which
confuses debugging; locking/SMP have made the layering violation (and
risks) of this more obvious over time.
Discussed with: green, bde, et al.
to not get a page fault if he has not defined a dump device.
Panic can often not do a dump as it can hang forever in some cases.
The original PR was for amd64 only. This is a generalised version of
that change.
PR: amd64/67712
Submitted by: wjw@withagen.nl <Willen Jan Withagen>
improved chance of working despite pressure from running programs.
Instead of trying to throw a bunch of pages out to swap and hope for
the best, only a range that can potentially fulfill contigmalloc(9)'s
request will have its contents paged out (potentially, not forcibly)
at a time.
The new contigmalloc operation still operates in three passes, but it
could potentially be tuned to more or less. The first pass only looks
at pages in the cache and free pages, so they would be thrown out
without having to block. If this is not enough, the subsequent passes
page out any unwired memory. To combat memory pressure refragmenting
the section of memory being laundered, each page is removed from the
systems' free memory queue once it has been freed so that blocking
later doesn't cause the memory laundered so far to get reallocated.
The page-out operations are now blocking, as it would make little sense
to try to push out a page, then get its status immediately afterward
to remove it from the available free pages queue, if it's unlikely to
have been freed. Another change is that if KVA allocation fails, the
allocated memory segment will be freed and not leaked.
There is a sysctl/tunable, defaulting to on, which causes the old
contigmalloc() algorithm to be used. Nonetheless, I have been using
vm.old_contigmalloc=0 for over a month. It is safe to switch at
run-time to see the difference it makes.
A new interface has been used which does not require mapping the
allocated pages into KVA: vm_page.h functions vm_page_alloc_contig()
and vm_page_release_contig(). These are what vm.old_contigmalloc=0
uses internally, so the sysctl/tunable does not affect their operation.
When using the contigmalloc(9) and contigfree(9) interfaces, memory
is now tracked with malloc(9) stats. Several functions have been
exported from kern_malloc.c to allow other subsystems to use these
statistics, as well. This invalidates the BUGS section of the
contigmalloc(9) manpage.
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
time now to break with the past: do not write the PID in the first note.
Rationale:
1. [impact of the breakage] Process IDs in core files serve no immediate
purpose to the debugger itself. They are only useful to relate a core
file to a process. This can provide context to the person looking at
the core file, provided one keeps track of this. Overall, not having
the PID in the core file is only in very rare occasions unfortunate.
2. [reason of the breakage] Having one PRSTATUS note contain the PID,
while all others contain the LWPID of the corresponding kernel thread
creates an irregularity for the debugger that cannot easily be worked
around. This is caused by libthread_db correlating user thread IDs to
kernel thread (aka LWP) IDs and thus aware of the actual LWPIDs.
Update comments accordingly.
that get certain types of control messages (ping6 and rtsol are
examples). This gets the new code closer to working:
1) Collect control mbufs for processing in the controlp ==
NULL case, so that they can be freed by externalize.
2) Loop over the list of control mbufs, as the externalize
function may not know how to deal with chains.
3) In the case where there is no externalize function,
remember to add the control mbuf to the controlp list so
that it will be returned.
4) After adding stuff to the controlp list, walk to the
end of the list of stuff that was added, incase we added
a chain.
This code can be further improved, but this is enough to get most
things working again.
Reviewed by: rwatson
NO_ADAPTIVE_MUTEXES. This option has been enabled by default on amd64 for
quite some time, and has been extensively tested on i386 and sparc64. It
shows measurable performance gains in many circumstances, and few negative
effects. It would be nice in t he future if adaptive mutexes actually went
to sleep after a certain amount of spinning, but that will require quite a
bit more testing.
earlier in unp_connect() so that vp->v_socket can't change between
our copying its value to a local variable and later use of that
variable. This may have been responsible for a panic during
shutdown that I experienced where simultaneous closing of a listen
socket by rpcbind and a new connection being made to rpcbind by
mountd.
values from either user land or from the kernel. Use them for
[gs]etsockopt and to clean up some calls to [gs]etsockopt in the
Linux emulation code that uses the stackgap.
since they are only accessed by curthread and thus do not need any
locking.
- Move pr_addr and pr_ticks out of struct uprof (which is per-process)
and directly into struct thread as td_profil_addr and td_profil_ticks
as these variables are really per-thread. (They are used to defer an
addupc_intr() that was too "hard" until ast()).
future:
rename ttyopen() -> tty_open() and ttyclose() -> tty_close().
We need the ttyopen() and ttyclose() for the new generic cdevsw
functions for tty devices in order to have consistent naming.
for unknown events.
A number of modules return EINVAL in this instance, and I have left
those alone for now and instead taught MOD_QUIESCE to accept this
as "didn't do anything".
line as the announcement. Someone should probably update the "buffers
remaining" message since we now no longer should have any buffers remaining
at that point.
Until now the function has just returned zero for any event, but
that is downright wrong for MOD_UNLOAD and not very useful for any
future events we add where it may be crucial to be able to tell
if the event was unhandled or successful.
Change the function to return as follows:
MOD_LOAD -> 0
MOD_UNLOAD -> EBUSY
anything else -> EOPNOTSUPP
check to ensure that the caller is not prison root.
The intention is to fix file descriptor creation so that
prison root can not use the last remaining file descriptors.
This privilege should be reserved for non-jailed root users.
Approved by: bmilekic (mentor)
sched_add() rather than just doing it in sched_wakeup(). The old
ithread preemption code used to set NEEDRESCHED unconditionally if it
didn't preempt which masked this bug in SCHED_4BSD.
Noticed by: jake
Reported by: kensmith, marcel
Add a MOD_QUIESCE event for modules. This should return error (EBUSY)
of the module is in use.
MOD_UNLOAD should now only fail if it is impossible (as opposed to
inconvenient) to unload the module. Valid reasons are memory references
into the module which cannot be tracked down and eliminated.
When kldunloading, we abandon if MOD_UNLOAD fails, and if -force is
not given, MOD_QUIESCE failing will also prevent the unload.
For backwards compatibility, we treat EOPNOTSUPP from MOD_QUIESCE as
success.
Document that modules should return EOPNOTSUPP for unknown events.
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
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
pmap_remove_pages(). (The implementation of pmap_remove_pages() is
optional. If pmap_remove_pages() is unimplemented, the acquisition and
release of the page queues lock is unnecessary.)
Remove spl calls from the alpha, arm, and ia64 pmap_remove_pages().
a better name. I have a kern_[sg]etsockopt which I plan to commit
shortly, but the arguments to these function will be quite different
from so_setsockopt.
Approved by: alfred
This is to allow filesystems to decide based on the passed thread
which vnode to return.
Several filesystems used curthread, they now use the passed thread.
will be used heavily in debugging KSE threads. This breaks libpthread
on IA64, but because libpthread was not in 5.2.1 release, I would like
to change it so we needn't to introduce another syscall.
tracing process to obtain information about the LWP that caused the
traced process to stop. Debuggers can use this information to select
the thread currently running on the LWP as the current thread.
The request has been made compatible with NetBSD for as much as
possible. This implementation differs from NetBSD in the following
ways:
1. The data argument is allowed to be smaller than the size of the
ptrace_lwpinfo structure known to the kernel, but not 0. This
is opposite to what NetBSD allows. The reason for this is that
we can extend the structure without affecting older binaries.
2. On NetBSD the tracing process is to set the pl_lwpid field to
the Id of the LWP it wants information of. We don't do that.
Our ptrace interface allows passing the LWP Id instead of the
PID. The tracing process is to set the PID to the LWP Id it
wants information of.
3. When the PID is actually the PID of the tracing process, this
request returns the information about the LWP that caused the
process to stop. This was the whole purpose of the request in
the first place.
When the traced process has exited, this request will return the
LWP Id 0, indicating that the process state is not the result of
an event specific to a LWP.
changing the backend from outside the KDB frontend. For example from
within a backend. Rewrite kdb_sysctl_current to make use of this
function as well.
in soreceive() after removing an MT_SONAME mbuf from the head of the
socket buffer.
When processing MT_CONTROL mbufs in soreceive(), first remove all of
the MT_CONTROL mbufs from the head of the socket buffer to a local
mbuf chain, then feed them into dom_externalize() as a set, which
both avoids thrashing the socket buffer lock when handling multiple
control mbufs, and also avoids races with other threads acting on
the socket buffer when the socket buffer mutex is released to enter
the externalize code. Existing races that might occur if the protocol
externalize method blocked during processing have also been closed.
Now that we synchronize socket buffer and stack state following
modifications to the socket buffer, turn the manual synchronization
that previously followed control mbuf processing with a set of
assertions. This can eventually be removed.
The soreceive() code is now substantially more MPSAFE.
the head of the mbuf chains in a socket buffer, re-synchronizes the
cache pointers used to optimize socket buffer appends. This will be
used by soreceive() before dropping socket buffer mutexes to make sure
a consistent version of the socket buffer is visible to other threads.
While here, update copyright to account for substantial rewrite of much
socket code required for fine-grained locking.
locking on 'nextrecord' and concerns regarding potentially inconsistent
or stale use of socket buffer or stack fields if they aren't carefully
synchronized whenever the socket buffer mutex is released. Document
that the high-level sblock() prevents races against other readers on
the socket.
Also document the 'type' logic as to how soreceive() guarantees that
it will only return one of normal data or inline out-of-band data.
name in the debug.kdb.current sysctl. All other dereferences are
properly guarded, but this one was overlooked.
Reported by: Morten Rodal (morten at rodal dot no)
associated with a PR_ADDR protocol, make sure to update the m_nextpkt
pointer of the new head mbuf on the chain to point to the next record.
Otherwise, when we release the socket buffer mutex, the socket buffer
mbuf chain may be in an inconsistent state.
o Make debugging code conditional upon KDB instead of DDB.
o s/WITNESS_DDB/WITNESS_KDB/g
o s/witness_ddb/witness_kdb/g
o Rename the debug.witness_ddb sysctl to debug.witness_kdb.
o Call kdb_backtrace() instead of backtrace().
o Call kdb_enter() instead Debugger().
o Assert kdb_active instead of db_active.
o Make debugging code conditional upon KDB instead of DDB.
o Call kdb_enter() instead of Debugger().
o Call kdb_backtrace() instead of db_print_backtrace() or backtrace().
kern_mutex.c:
o Replace checks for db_active with checks for kdb_active and make
them unconditional.
kern_shutdown.c:
o s/DDB_UNATTENDED/KDB_UNATTENDED/g
o s/DDB_TRACE/KDB_TRACE/g
o Save the TID of the thread doing the kernel dump so the debugger
knows which thread to select as the current when debugging the
kernel core file.
o Clear kdb_active instead of db_active and do so unconditionally.
o Remove backtrace() implementation.
kern_synch.c:
o Call kdb_reenter() instead of db_error().
in which multiple (presumably different) debugger backends can be
configured and which provides basic services to those backends.
Besides providing services to backends, it also serves as the single
point of contact for any and all code that wants to make use of the
debugger functions, such as entering the debugger or handling of the
alternate break sequence. For this purpose, the frontend has been
made non-optional.
All debugger requests are forwarded or handed over to the current
backend, if applicable. Selection of the current backend is done by
the debug.kdb.current sysctl. A list of configured backends can be
obtained with the debug.kdb.available sysctl. One can enter the
debugger by writing to the debug.kdb.enter sysctl.
Add copyiniov() which copies a struct iovec array in from userland into
a malloc'ed struct iovec. Caller frees.
Change uiofromiov() to malloc the uio (caller frees) and name it
copyinuio() which is more appropriate.
Add cloneuio() which returns a malloc'ed copy. Caller frees.
Use them throughout.
assigning a pointer to the list and then dereferencing the pointer as a
second step. When the first spin lock is acquired, curthread is not in
a critical section so it may be preempted and would end up using another
CPUs lock list instead of its own.
When this code was in witness_lock() this sequence was safe as curthread
was in a critical section already since witness_lock() is called after the
lock is acquired.
Tested by: Daniel Lang dl at leo.org
takes an argument to specify if it should preempt or not. Don't preempt
when sched_add_internal() is called from kseq_idled() or kseq_assign()
as in those cases we are about to call mi_switch() anyways. Also, doing
so during the first context switch on an AP leads to a NULL pointer deref
because curthread is NULL.
- Reenable preemption for ULE.
Submitted by: Taku YAMAMOTO taku at tackymt.homeip.net
When avoiding the zeroing of "bogus_page" when it appears in a buf,
be sure to advance the pointers into the data for successive pages.
The bug caused file corruption when read(2)ing from a "hole" in a
file where a previous page of the read block had already been faulted
in: fsx tripped up on this pretty quickly. The particular access
pattern is probably pretty unusual, so other applications probably
wouldn't have had problems, but you'd never know.
Reviewed By: alc@
Rebind the client socket when we experience a timeout. This fixes
the case where our IP changes for some reason.
Signal a VFS event when NFS transitions from up to down and vice
versa.
Add a placeholder vfs_sysctl where we will put status reporting
shortly.
Also:
Make down NFS mounts return EIO instead of EINTR when there is a
soft timeout or force unmount in progress.
hangs due to recent preemption changes. This change appears to remove
the panic that I was running into, but at the cost of increasing
ithread scheduling latency, and as such is a temporary band-aid until
jhb has a chance to resolve the ule<->preemption interaction that is
the source of the problem. If it doesn't fix the problem for others--
sorry!
so that last_work_seen has a reasonable value at the transition
to the SYNCER_SHUTTING_DOWN state, even if net_worklist_len happened
to be zero at the time.
Initialize last_work_seen to zero as a safety measure in case the
syncer never ran in the SYNCER_RUNNING state.
Tested by: phk
Speed up the syncer when shutting down by sleeping for a shorter
period of time instead of cranking up rushjob and using the
normal one second sleep.
Skip empty worklist slots when shutting down to avoid lengthy
intervals of inactivity.
Give I/O more time to complete between steps by not speeding the
syncer quite as much.
Terminate the syncer after one full pass through the worklist
plus one second with the worklist containing nothing but syncer
vnodes.
Print an indication of shutdown progress to the console.
Add a sysctl, vfs.worklist_len, to allow the size of the syncer worklist
to be monitored.
around in the vnodes surroundings when we allocate a block.
Assign a blocksize when we create a vnode, and yell a warning (and ignore it)
if we got the wrong size.
Please email all such warnings to me.
generic filesystem events to userspace. Currently only mount and unmount
of filesystems are signalled. Soon to be added, up/down status of NFS.
Introduce a sysctl node used to route requests to/from filesystems
based on filesystem ids.
Introduce a new vfsop, vfs_sysctl(mp, req) that is used as the callback/
entrypoint by the sysctl code to change individual filesystems.
ffs_mount -> bdevvp -> getnewvnode(..., mp = NULL, ...) ->
insmntqueue(vp, mp = NULL) -> KASSERT -> panic
Make getnewvnode() only call insmntqueue() if the mountpoint parameter
is not NULL.
our cached 'next vnode' being removed from this mountpoint. If we
find that it was recycled, we restart our traversal from the start
of the list.
Code to do that is in all local disk filesystems (and a few other
places) and looks roughly like this:
MNT_ILOCK(mp);
loop:
for (vp = TAILQ_FIRST(&mp...);
(vp = nvp) != NULL;
nvp = TAILQ_NEXT(vp,...)) {
if (vp->v_mount != mp)
goto loop;
MNT_IUNLOCK(mp);
...
MNT_ILOCK(mp);
}
MNT_IUNLOCK(mp);
The code which takes vnodes off a mountpoint looks like this:
MNT_ILOCK(vp->v_mount);
...
TAILQ_REMOVE(&vp->v_mount->mnt_nvnodelist, vp, v_nmntvnodes);
...
MNT_IUNLOCK(vp->v_mount);
...
vp->v_mount = something;
(Take a moment and try to spot the locking error before you read on.)
On a SMP system, one CPU could have removed nvp from our mountlist
but not yet gotten to assign a new value to vp->v_mount while another
CPU simultaneously get to the top of the traversal loop where it
finds that (vp->v_mount != mp) is not true despite the fact that
the vnode has indeed been removed from our mountpoint.
Fix:
Introduce the macro MNT_VNODE_FOREACH() to traverse the list of
vnodes on a mountpoint while taking into account that vnodes may
be removed from the list as we go. This saves approx 65 lines of
duplicated code.
Split the insmntque() which potentially moves a vnode from one mount
point to another into delmntque() and insmntque() which does just
what the names say.
Fix delmntque() to set vp->v_mount to NULL while holding the
mountpoint lock.
