are places where the "main thread" of the booting kernel (either the
thread which later becomes swapper or the thread which later becomes
init) has to stop and wait for action to take place in another thread
before continuing.
There are currently three such holds:
1. The intr_config_hooks SYSINIT waits for hooks registered via the
config_intrhook_establish function; this allows (typically) devices
which need interrupts enabled to complete their initialization to do
so before root is mounted.
2. The g_waitidle function waits for the GEOM event queue to be empty;
this ensures that all of the disks which have been attached have been
tasted before we attempt to mount root.
3. The vfs_mountroot_wait function (in addition to calling g_waitidle)
waits for holds registered via root_mount_hold; among other things, this
is used by the USB subsystem to ensure that we don't fail to mount root
if it's located on a USB disk which takes a while to probe.
METHOD and STATICMETHOD declarations; that code will be inserted
into the dispatch function before and after the method call.
Use this functionality and the TSLOG framework to record DEVICE_ATTACH
and DEVICE_PROBE entry/exit timestamps.
independent functions with important roles in the early boot process:
mi_startup (with the "exit" recorded when it becomes swapper),
start_init (with the "exit" recorded when the thread is about to
"return" into the newly created init process), vfs_mountroot, and
vfs_mountroot_wait.
This is a very primitive system, intended for use in measuring performance
during the early system boot, before more sophisticated tools like DTrace
or infrastructure like kernel memory allocation and mutexes are available.
Because this code records pointers to strings rather than copying strings
(in order to keep the memory usage more manageable), if a kernel module is
unloaded after logging an event, Bad Things can happen. Users are advised
to not do that.
Since cycle counts from the early kernel boot are used as an initial entropy
source, publishing this information to userland could result in inadequate
entropy being kept private to the kernel RNG. Users are advised to not
enable this on systems with untrusted users.
Discussed on: freebsd-current
Both files originated in NetBSD:
sysv_ipc.c CVS 1.9:
Most of their changes don't apply to us as we already have similar
changes. This is a better reference for future merges.
sysv_shm.c CVS 1.39:
Most of their changes don't apply to our code but interestingly this
revision merged our changes and is a better point for reference.
Move the VCS tags to the position recommended in our committers guide
(section 8),
No functional change.
In both rw and sx locks we always go to sleep if the lock owner is not
running.
We do spin for some time if the lock is read-locked.
However, if we decide to go to sleep due to the lock owner being off cpu
and after sleepq/turnstile gets acquired the lock is read-locked, we should
fallback to the aforementioned wait.
Since this function is effectively slow path, if we get here the lock is most
likely already taken in which case it is cheaper to not blindly attempt the
atomic op.
While here move hwpmc probe out of the loop to match other primitives.
vmmap_skip_res_cnt control check inside it.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D13595
This reduces noise when kernel is compiled by newer GCC versions,
such as one used by external toolchain ports.
Reviewed by: kib, andrew(sys/arm and sys/arm64), emaste(partial), erj(partial)
Reviewed by: jhb (sys/dev/pci/* sys/kern/vfs_aio.c and sys/kern/kern_synch.c)
Differential Revision: https://reviews.freebsd.org/D10385
restart_cpus() worked well enough by accident. Before this set of fixes,
resume_cpus() used the same cpuset (started_cpus, meaning CPUs directed to
restart) as restart_cpus(). resume_cpus() waited for the wrong cpuset
(stopped_cpus) to become empty, but since mixtures of stopped and suspended
CPUs are not close to working, stopped_cpus must be empty when resuming so
the wait is null -- restart_cpus just allows the other CPUs to restart and
returns without waiting.
Fix resume_cpus() to wait on a non-wrong cpuset for the ACPI case, and
add further kludges to try to keep it working for the XEN case. It
was only used for XEN. It waited on suspended_cpus. This works for
XEN. However, for ACPI, resuming is a 2-step process. ACPI has already
woken up the other CPUs and removed them from suspended_cpus. This
fix records the move by putting them in a new cpuset resuming_cpus.
Waiting on suspended_cpus would give the same null wait as waiting on
stopped_cpus. Wait on resuming_cpus instead.
Add a cpuset toresume_cpus to map the CPUs being told to resume to keep
this separate from the cpuset started_cpus for mapping the CPUs being told
to restart. Mixtures of stopped and suspended/resuming CPUs are still far
from working. Describe new and some old cpusets in comments.
Add further kludges to cpususpend_handler() to try to avoid breaking it
for XEN. XEN doesn't use resumectx(), so it doesn't use the second
return path for savectx(), and it goes from the suspended state directly
to the restarted state, while ACPI resume goes through the resuming state.
Enter the resuming state early for all cases so that resume_cpus can test
for being in this state and not have to worry about the intermediate
!suspended state for ACPI only.
Reviewed by: kib
On the one hand, FIFOs should respect other variables not supported by
the fifofs vnode operation (such as _PC_NAME_MAX, _PC_LINK_MAX, etc.).
These values are fs-specific and must come from a fs-specific method.
On the other hand, filesystems that support FIFOs are required to
support _PC_PIPE_BUF on directory vnodes that can contain FIFOs.
Given this latter requirement, once the fs-specific VOP_PATHCONF
method supports _PC_PIPE_BUF for directories, it is also suitable for
FIFOs permitting a single VOP_PATHCONF method to be used for both
FIFOs and non-FIFOs.
To that end, retire all of the FIFO-specific pathconf methods from
filesystems and change FIFO-specific vnode operation switches to use
the existing fs-specific VOP_PATHCONF method. For fifofs, set it's
VOP_PATHCONF to VOP_PANIC since it should no longer be used.
While here, move _PC_PIPE_BUF handling out of vop_stdpathconf() so that
only filesystems supporting FIFOs will report a value. In addition,
only report a valid _PC_PIPE_BUF for directories and FIFOs.
Discussed with: bde
Reviewed by: kib (part of a larger patch)
MFC after: 1 month
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D12572
Having all filesystems fall through to default values isn't always correct
and these values can vary for different filesystem implementations. Most
of these changes just use the existing default values with a few exceptions:
- Don't report CHOWN_RESTRICTED for ZFS since it doesn't do the exact
permissions check this claims for chown().
- Use NANDFS_NAME_LEN for NAME_MAX for nandfs.
- Don't report a LINK_MAX of 0 on smbfs. Now fail with EINVAL to
indicate hard links aren't supported.
Requested by: bde (though perhaps not this exact implementation)
Reviewed by: kib (earlier version)
MFC after: 1 month
Sponsored by: Chelsio Communications
The method handles NAME_MAX and LINK_MAX explicitly. For all other
pathconf variables, the method passes the request down to the underlying
file descriptor. This requires splitting a kern_fpathconf() syscallsubr
routine out of sys_fpathconf(). Also, to avoid lock order reversals with
vnode locks, the fdescfs vnode is unlocked around the call to
kern_fpathconf(), but with the usecount of the vnode bumped.
MFC after: 1 month
Sponsored by: Chelsio Communications
In this case volatile qualifiers enusre that a compiler does not
optimize the accesses out.
Reviewed by: alc, jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D13534
This variable should be pure MI except possibly for reading it in MD
dump routines. Its initialization was pure MD in 4.4BSD, but FreeBSD
changed this in r36441 in 1998. There were many imperfections in
r36441. This commit fixes only a small one, to simplify fixing the
others 1 arch at a time. (r47678 added support for
special/early/multiple message buffer initialization which I want in
a more general form, but this was too fragile to use because hacking
on the msgbufp global corrupted it, and was only used for 5 hours in
-current...)
A correct destruction is important for WITNESS(4) and LOCK_PROFILING(9).
Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de>
MFC after: 1 week
started, but also by the turnstiles to mark a thread as runnable for
all locks, for instance sleepqueues do:
setrunnable()->sched_wakeup()->sched_add()
In r326218 code was added to allow booting from non-zero CPU numbers
by setting the ts_cpu field inside the ULE scheduler's sched_add()
function. This had an undesired side-effect that prior sched_pin() and
sched_bind() calls got disregarded. This patch fixes the
initialization of the ts_cpu field for the ULE scheduler to only
happen once when the initial thread is constructed during system
init. Forking will then later on ensure that a valid ts_cpu value gets
copied to all children.
Reviewed by: jhb, kib
Discussed with: nwhitehorn
MFC after: 1 month
Differential revision: https://reviews.freebsd.org/D13298
Sponsored by: Mellanox Technologies
The arena argument to kmem_*() is now only used in an assert. A follow-up
commit will remove the argument altogether before we freeze the API for the
next release.
This replaces the hard limit on kmem size with a soft limit imposed by UMA. When
the soft limit is exceeded we periodically wakeup the UMA reclaim thread to
attempt to shrink KVA. On 32bit architectures this should behave much more
gracefully as we exhaust KVA. On 64bit the limits are likely never hit.
Reviewed by: markj, kib (some objections)
Discussed with: alc
Tested by: pho
Sponsored by: Netflix / Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D13187
is up to the caller to check for a NULL return value. The assert was meant
to catch buggy code that did not check the return value. Some code, however,
was smart and used the return value to see if a CPU existed, which this
broke.
Requested by: jhb@
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
When waiters/writer spinner flags are set no new readers can show up unless
they already have a different rw rock read locked. The change in r326195 failed
to take that into account - in presence of new readers it would spin until
they all drain, which would be lead to trouble if e.g. they go off cpu and
can get scheduled because of this thread.
Reported by: pho
sleepq is only locked if the curhtread is the last reader. By the time
the lock gets acquired new ones could have arrived. The previous code
would unlock and loop back. This results spurious relocking of sleepq.
This is a step towards xadd-based unlock routine.
In order to go to sleep threads set waiter flags, but that can spuriously
fail e.g. when a new reader arrives. Instead of unlocking everything and
looping back, re-evaluate the new state while still holding the lock necessary
to go to sleep.
- Add a new KTR_STRUCT_ARRAY ktrace record type which dumps an array of
structures.
The structure name in the record payload is preceded by a size_t
containing the size of the individual structures. Use this to
replace the previous code that dumped the kevent arrays dumped for
kevent(). kdump is now able to decode the kevent structures rather
than dumping their contents via a hexdump.
One change from before is that the 'changes' and 'events' arrays are
not marked with separate 'read' and 'write' annotations in kdump
output. Instead, the first array is the 'changes' array, and the
second array (only present if kevent doesn't fail with an error) is
the 'events' array. For kevent(), empty arrays are denoted by an
entry with an array containing zero entries rather than no record.
- Move kevent decoding tables from truss to libsysdecode.
This adds three new functions to decode members of struct kevent:
sysdecode_kevent_filter, sysdecode_kevent_flags, and
sysdecode_kevent_fflags.
kdump uses these helper functions to pretty-print kevent fields.
- Move structure definitions for freebsd11 and freebsd32 kevent
structures to <sys/event.h> so that they can be shared with userland.
The 32-bit structures are only exposed if _WANT_KEVENT32 is defined.
The freebsd11 structures are only exposed if _WANT_FREEBSD11_KEVENT is
defined. The 32-bit freebsd11 structure requires both.
- Decode freebsd11 kevent structures in truss for the compat11.kevent()
system call.
- Log 32-bit kevent structures via ktrace for 32-bit compat kevent()
system calls.
- While here, constify the 'void *data' argument to ktrstruct().
Reviewed by: kib (earlier version)
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D12470
Upon successful completion, the execve() system call invokes
exec_setregs() to initialize the registers of the initial thread of the
newly executed process. What is weird is that when execve() returns, it
still goes through the normal system call return path, clobbering the
registers with the system call's return value (td->td_retval).
Though this doesn't seem to be problematic for x86 most of the times (as
the value of eax/rax doesn't matter upon startup), this can be pretty
frustrating for architectures where function argument and return
registers overlap (e.g., ARM). On these systems, exec_setregs() also
needs to initialize td_retval.
Even worse are architectures where cpu_set_syscall_retval() sets
registers to values not derived from td_retval. On these architectures,
there is no way cpu_set_syscall_retval() can set registers to the way it
wants them to be upon the start of execution.
To get rid of this madness, let sys_execve() return EJUSTRETURN. This
will cause cpu_set_syscall_retval() to leave registers intact. This
makes process execution easier to understand. It also eliminates the
difference between execution of the initial process and successive ones.
The initial call to sys_execve() is not performed through a system call
context.
Reviewed by: kib, jhibbits
Differential Revision: https://reviews.freebsd.org/D13180
