1. There was a race condition between a thread unlocking
a umtx and the thread contesting it. If the unlocking
thread won the race it may try to wakeup a thread that
was not yet in msleep(). The contesting thread would then
go to sleep to await a wakeup that would never come. It's
not possible to close the race by using a lock because
calls to casuptr() may have to fault a page in from swap.
Instead, the race was closed by introducing a flag that
the unlocking thread will set when waking up a thread.
The contesting thread will check for this flag before
going to sleep. For now the flag is kept in td_flags,
but it may be better to use some other member or create
a new one because of the possible performance/contention
issues of having to own sched_lock. Thanks to jhb for
pointing me in the right direction on this one.
2. Once a umtx was contested all future locks and unlocks
were happening in the kernel, regardless of whether it
was contested or not. To prevent this from happening,
when a thread locks a umtx it checks the queue for that
umtx and unsets the contested bit if there are no other
threads waiting on it. Again, this is slightly more
complicated than it needs to be because we can't hold
a lock across casuptr(). So, the thread has to check
the queue again after unseting the bit, and reset the
contested bit if it finds that another thread has put
itself on the queue in the mean time.
3. Remove the if... block for unlocking an uncontested
umtx, and replace it with a KASSERT. The _only_ time
a thread should be unlocking a umtx in the kernel is
if it is contested.
large to huge amounts of small or medium sized receive buffers. The problem
with these situations is that they eat up the available DMA address space
very quickly when using mbufs or even mbuf clusters. Additionally this
facility provides a direct mapping between 32-bit integers and these buffers.
This is needed for devices originally designed for 32-bit systems. Ususally
the virtual address of the buffer is used as a handle to find the buffer as
soon as it is returned by the card. This does not work for 64-bit machines
and hence this mapping is needed.
multiple mutex pools with different options and sizes. Mutex pools can
be created with either the default sleep mutexes or with spin mutexes.
A dynamically created mutex pool can now be destroyed if it is no longer
needed.
Create two pools by default, one that matches the existing pool that
uses the MTX_NOWITNESS option that should be used for building higher
level locks, and a new pool with witness checking enabled.
Modify the users of the existing mutex pool to use the appropriate pool
in the new implementation.
Reviewed by: jhb
immediately after the kernel map has been sized, and is
the optimal place for the autosizing of memory allocations
which occur within the kernel map to occur.
Suggested by: bde
- Use atomic ops to update the bigpipe count
- Make the bigpipe count sysctl readable
- Remove a duplicate comparison in an if statement
- Comment two SYSCTLs.
than the shortcircuited version I had been using, which only worked
properly on i386 & amd64.
Also, change an autoscale constant to account for the more correct
kmem_map size.
Problem noticed by: mux
- Limit the total number of pipes so that we do not
exhaust all vm objects in the kernel map. When
this limit is reached, a ratelimited message will
be printed to the console.
- Put a soft limit on the amount of memory consumable
by pipes. Once the limit has been reached, all new
pipes will be limited to 4K in size, rather than the
default of 16K.
- Put a limit on the number of pages that may be used
for high speed page flipping in order to reduce the
amount of wired memory. Pipe writes that occur
while this limit is exceeded will fall back to
non-page flipping mode.
The above values are auto-tuned in subr_param.c and
are scaled to take into account both the size of
physical memory and the size of the kernel map.
These limits help to reduce the "kernel resources exhausted"
panics that could be caused by opening a large
number of pipes. (Pipes alone are no longer able
to exhaust all resources, but other kernel memory hogs
in league with pipes may still be able to do so.)
PR: 53627
Ideas / comments from: hsu, tjr, dillon@apollo.backplane.com
MFC after: 1 week
notice another typo in the same line. This typo makes libthr unuseable,
but it's effects where counter-balanced by the extra semicolon, which
made libthr remarkably useable for the past several months.
- Associate logical CPUs on the same physical core with the same kseq.
- Adjust code that assumed there would only be one running thread in any
kseq.
- Wrap the HTT code with a ULE_HTT_EXPERIMENTAL ifdef. This is a start
towards HyperThreading support but it isn't quite there yet.
as the target process' pid, it may exist if the process forked before leaving
the pgrp.
Thix fixes a panic that happens when calling setpgid to make a process
re-enter the pgrp with the same pgid as its pid if the pgrp still exists.
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)
locks held by each thread.
- Fix a bug in the original BSD/OS code where a contested lock was not
properly handed off from the old thread to the new thread when a
contested lock with more than one blocked thread was transferred from
one thread to another.
- Don't use an atomic operation to write the MTX_CONTESTED value to
mtx_lock in the aforementioned special case. The memory barriers and
exclusion provided by sched_lock are sufficient.
Spotted by: alc (2)
system by specifying the file system ID instead of a path. Use this
by default in umount(8). This avoids the need to perform any vnode
operations to look up the mount point, so it makes it possible to
unmount a file system whose root vnode cannot be looked up (e.g.
due to a dead NFS server, or a file system that has become detached
from the hierarchy because an underlying file system was unmounted).
It also provides an unambiguous way to specify which file system is
to be unmunted.
Since the ability to unmount using a path name is retained only for
compatibility, that case now just uses a simple string comparison
of the supplied path against f_mntonname of each mounted file system.
Discussed on: freebsd-arch
mdoc help from: ru
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)
POSIX says siginfo pointer parameter can be NULL and if the
function success, it should return signal number but not zero.
The waitset it past should be negatived before it can be
used as thread signal mask.
nice distribution without significantly impacting interactive response.
As a side effect it should also allow batch processes to run for a
slightly longer period which will positively impact their performance.
This commit has two pieces. One half is the watchdog kernel code which lives
primarily in hardclock() in sys/kern/kern_clock.c. The other half is a userland
daemon which, when run, will keep the watchdog from firing while the userland
is intact and functioning.
Approved by: jeff (mentor)
Before, we would add/subtract the leap second when the system had been
up for an even multiple of days, rather than at the end of the day, as
a leap second is defined (at least wrt ntp). We do this by
calculating the notion of UTC earlier in the loop, and passing that to
get it adjusted. Any adjustments that ntp_update_second makes to this
time are then transferred to boot time. We can't pass it either the
boot time or the uptime because their sum is what determines when a
leap second is needed. This code adds an extra assignment and two
extra compare in the typical case, which is as cheap as I could made
it.
I have confirmed with this code the kernel time does the correct thing
for both positive and negative leap seconds. Since the ntp interface
doesn't allow for +2 or -2, those cases can't be tested (and the folks
in the know here say there will never be a +2s or -2s leap event, but
rather two +1s or -1s leap events).
There will very likely be no leap seconds for a while, given how the
earth is speeding up and slowing down, so there will be plenty of time
for this fix to propigate. UT1-UTC is currently at "about -0.4s" and
decrementing by .1s every 8 months or so. 6 * 8 is 48 months, or 4
years.
-stable has different code, but a similar bug that was introduced
about the time of the last leap second, which is why nobody has
noticed until now.
MFC After: 3 weeks
Reviewed by: phk
"Furthermore, leap seconds must die." -- Cato the Elder
incremented at the start of the leap second, not after the leap second
has been inserted. This is because at the start of the leap second,
we set the time back one second. This setting back one second is the
moment that the offset changes. The old code set it back after the
leap second, but that's one second too late. The negative leap second
case is handled correctly.
Reviewed by: phk
the MAC policy modules to improve robustness against C string
bugs and vulnerabilities. Following these revisions, all
string construction of labels for export to userspace (or
elsewhere) is performed using the sbuf API, which prevents
the consumer from having to perform laborious and intricate
pointer and buffer checks. This substantially simplifies
the externalization logic, both at the MAC Framework level,
and in individual policies; this becomes especially useful
when policies export more complex label data, such as with
compartments in Biba and MLS.
Bundled in here are some other minor fixes associated with
externalization: including avoiding malloc while holding the
process mutex in mac_lomac, and hence avoid a failure mode
when printing labels during a downgrade operation due to
the removal of the M_NOWAIT case.
This has been running in the MAC development tree for about
three weeks without problems.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
attributes from objects over vop_setextattr() with a NULL uio; if
the file system doesn't support the vop_rmextattr() method, fall
back to the vop_setextattr() method.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
interface, rather than relying on a NULL uio for the deletion
operation.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
specify what credential to use when authorizing vn_open() and later
write operations, rather than curthread->td_ucred.
When writing KTR traces to an ALQ, specify the credential of the thread
generating the sysctl request.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories
Several of the subtypes have an associated vnode which is used for
stuff like the f*() functions.
By giving the vnode a speparate field, a number of checks for the specific
subtype can be replaced simply with a check for f_vnode != NULL, and
we can later free f_data up to subtype specific use.
At this point in time, f_data still points to the vnode, so any code I
might have overlooked will still work.
console, even if there is a TIOCCONS console tty. We were already
doing this after a panic, but it's also useful when entering DDB
for some other reason too.
TIOCCONS console (e.g. xconsole) via a timeout routine instead of
calling into the tty code directly from printf(). This fixes a
number of cases where calling printf() at the wrong time (such as
with locks held) would cause a panic if xconsole is running.
The TIOCCONS message buffer is 8k in size by default, but this can
be changed with the kern.consmsgbuf_size sysctl. By default, messages
are checked for 5 times per second. The timer runs and the buffer
memory remains allocated only at times when a TIOCCONS console is
active.
Discussed on: freebsd-arch
with a new implementation that has a mostly reentrant "addchar"
routine, supports multiple message buffers in the kernel, and hides
the implementation details from callers.
The new code uses a kind of sequence number to represend the current
read and write positions in the buffer. This approach (suggested
mainly by bde) permits the read and write pointers to be maintained
separately, which reduces the number of atomic operations that are
required. The "mostly reentrant" above refers to the way that while
it is now always safe to have any number of concurrent writers,
readers could see the message buffer after a writer has advanced
the pointers but before it has witten the new character.
Discussed on: freebsd-arch
causing poor interactive performance while unnice processes were running.
The new scheme still allows nice to have an effect on priority but it is
not as dramatic as the effect of the interactivity score.
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
threads in the process have already masked the signal, so job control
is delayed. But later a thread unmasking the STOP signal should enable
job control, so in issignal(), scanning all threads in process to see
if we can direct suspend some of them, not just suspend current thread.
we can deadlock because of lock order reversals. This was not
caught because Witness ignores pool mutexes right now.
Diagnosis and help: truckman
Noticed by: pho
"maxproc limit exceeded by uid %i, please see tuning(7) and login.conf(5)."
Which will be triggered whenever a user hits his/her maxproc limit or
the systemwide maxproc limit is reached.
MFC after: 1 week
mutexes are supposed to only be used as leaf mutexes, and what appear
to be separate pool mutexes could be aliased together, it is bad idea
for a thread to attempt to hold two pool mutexes at the same time.
Slightly rearrange the code in kern_open() so that FILE_UNLOCK() is
called before calling VOP_GETVOBJECT(), which will grab the v_vnlock
mutex.
systems to fail more gracefully when a file descriptor exhaustion situation
occurs.
Original patch by: David G. Andersen <dga@lcs.mit.edu>
PR: 45353
MFC after: 1 week
because the run time exceeds the largest value a signed int can hold.
The real solution involves calculating how far we are over the limit.
To quickly solve this problem we loop removing 1/5th of the current value
until it falls below the limit. The common case requires no passes.
and run time.
- Scale the sleep and run time back via sched_interact_update() in more
places. This is to keep the statistic more accurate.
- Charge a parent one tick for forking a child.
- Add only the run time and not the sleep time to the parents kg when a
thread exits. This allows us to give a penalty for having an expensive
thread exit but does not give a bonus for having an interactive thread
exit.
- Change the SLP_RUN_THROTTLE to limit us to 4/5th and not 1/2.
- Change the SLP_RUN_MAX to two seconds. This keeps bursty interactive
applications like mozilla and openoffice in the interactive range even
through expensive tasks.
- Recalculate the slice after every sleep. This ensures that once a task
has been marked interactive it only has a slice of 1 at the risk of
giving tasks that sleep for a very brief period a longer time slice.
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.
panics. Before revision 1.38, we used to just point panicstr at the
format string if panicstr was NULL, but since we now use a static
buffer for the formatted panic message, we have to be careful to
only write to it during the first panic.
Pointed out by: bde
which meant no process would run for longer than 20ms.
- Slightly redo the interactivity scorer. It follows the same algorithm but
in a slightly more correct way. Previously values above half were
incorrect.
- Lower the interactivity threshold to 20. It seems that in testing non-
interactive tasks are hardly ever near there and expensive interactive
tasks can sometimes surpass it. This area needs more testing.
- Remove an unnecessary KTR.
- Fix a case where an idle thread that had an elevated priority due to
priority prop. would be placed back on the idle queue.
- Delay setting NEEDRESCHED until userret() for threads that haad their
priority elevated while in kernel. This gives us the same context switch
optimization as SCHED_4BSD.
- Limit the child's slice to 1 in sched_fork_kse() so we detect its behavior
more quickly.
- Inhert some of the run/slp time from the child in sched_exit_ksegrp().
- Redo some of the priority comparisons so they are more clear.
- Throttle the frequency of sched_pctcpu_update() so that rounding errors
do not make it invalid.
to the machine-independent parts of the VM. At the same time, this
introduces vm object locking for the non-i386 platforms.
Two details:
1. KSTACK_GUARD has been removed in favor of KSTACK_GUARD_PAGES. The
different machine-dependent implementations used various combinations
of KSTACK_GUARD and KSTACK_GUARD_PAGES. To disable guard page, set
KSTACK_GUARD_PAGES to 0.
2. Remove the (unnecessary) clearing of PG_ZERO in vm_thread_new. In
5.x, (but not 4.x,) PG_ZERO can only be set if VM_ALLOC_ZERO is passed
to vm_page_alloc() or vm_page_grab().
small but noticeable increase in performance for name lookup operations.
The code uses two zones, one for short names (less than 32 characters)
and one for long names (up to NAME_MAX). Since most file names are
fairly short, this saves a considerable amount of space that would
otherwise be wasted if we always allocated NAME_MAX bytes. The cutoff
value of 32 characters was picked arbitrarily and may benefit from some
tweaking; it could also be made into a tunable.
Submitted by: hmp
