Commit Graph

18 Commits

Author SHA1 Message Date
David Xu
0cb7166f78 Remove thread_upcall_check, it was used to avoid race bug in earlier
day's sleep queue code, today the bug no longer exists.
please see 04/25/2004 freebsd-threads@ mailing list archive.
2005-05-27 15:57:27 +00:00
John Baldwin
95b66e9e53 Close a race between sleepq_broadcast() and sleepq_catch_signals().
Specifically, sleepq_broadcast() uses td_slpq for its private pending
queue of threads that it is going to wake up after it takes them off the
sleep queue.  The problem is that if one of the threads is actually not
asleep yet, then we can end up with td_slpq being corrupted and/or the
thread being made runnable at the wrong time resulting in the td_sleepqueue
== NULL assertion failures occasionally reported under heavy load.

The fix is to stop being so fancy and ditch the whole pending queue bit.
Instead, sleepq_remove_thread() and sleepq_resume_thread() were merged
into one function that requires the caller to hold sched_lock.  This
fixes several places that unlocked sched_lock only to call a function
that then locked sched_lock, so even though sched_lock is now held
slightly longer, removing the extra lock acquires (1 pair instead of 3
in some cases) probably makes it an overall win if you don't include the
fact that it closes a race.  This is definitely a 5.4 candidate.

PR:		kern/79693
Submitted by:	Steven Sears stevenjsears at yahoo dot com
MFC after:	4 days
2005-04-14 06:30:32 +00:00
Poul-Henning Kamp
c711aea6ca Make a bunch of malloc types static.
Found by:	src/tools/tools/kernxref
2005-02-10 12:02:37 +00:00
Warner Losh
9454b2d864 /* -> /*- for copyright notices, minor format tweaks as necessary 2005-01-06 23:35:40 +00:00
John Baldwin
bd1d11f5dc - Store threads on sleep queues in FIFO order rather than sorted by
priority.  The sleep queues don't get updated when the priority of
  threads changes, so sleepq_signal() might not always wakeup the
  highest priority thread.  Updating the queues when thread priorities
  change cannot be easily done due to lock orders, so instead we do an
  O(n) walk of the queue for a sleepq_signal() operation instead of O(1).
  On the other hand, adding a thread to a sleep queue now goes from O(n)
  to O(1) so it ends up as an even tradeoff.  The correctness here with
  regards to priorities is actually fairly important.  msleep() gives
  interactive threads their priority "boost" after they are placed on the
  queue, but before this fix that "boost" wasn't used to determine the
  highest priority thread that sleepq_signal() awoke.
- Fix up some comments.

Inspired by:	ups, bde
2004-11-05 20:19:58 +00:00
John Baldwin
2ff0e645d1 Refine the turnstile and sleep queue interfaces just a bit:
- Add a new _lock() call to each API that locks the associated chain lock
  for a lock_object pointer or wait channel.  The _lookup() functions now
  require that the chain lock be locked via _lock() when they are called.
- Change sleepq_add(), turnstile_wait() and turnstile_claim() to lookup
  the associated queue structure internally via _lookup() rather than
  accepting a pointer from the caller.  For turnstiles, this means that
  the actual lookup of the turnstile in the hash table is only done when
  the thread actually blocks rather than being done on each loop iteration
  in _mtx_lock_sleep().  For sleep queues, this means that sleepq_lookup()
  is no longer used outside of the sleep queue code except to implement an
  assertion in cv_destroy().
- Change sleepq_broadcast() and sleepq_signal() to require that the chain
  lock is already required.  For condition variables, this lets the
  cv_broadcast() and cv_signal() functions lock the sleep queue chain lock
  while testing the waiters count.  This means that the waiters count
  internal to condition variables is no longer protected by the interlock
  mutex and cv_broadcast() and cv_signal() now no longer require that the
  interlock be held when they are called.  This lets consumers of condition
  variables drop the lock before waking other threads which can result in
  fewer context switches.

MFC after:	1 month
2004-10-12 18:36:20 +00:00
Stephan Uphoff
c6a08cf2d7 Directly modifying the priority of a thread that may be on the runqueue
can break the sorting order of the ksegp run queue.

Tested   by: pho
Reviewed by: jhb, julian
Approved by: sam (mentor)
MFC: ASAP
2004-10-12 16:31:23 +00:00
John Baldwin
007ddf7e7a Now that the return value semantics of cv's for multithreaded processes
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.
2004-08-19 11:31:42 +00:00
John Baldwin
bf0acc273a - Change mi_switch() and sched_switch() to accept an optional thread to
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.
2004-07-02 19:09:50 +00:00
John Baldwin
ef0ebfc351 Add two new kernel options to allow rudimentary profiling of the internal
hash tables used in the sleep queue and turnstile code.  Each option adds
a sysctl tree under debug containing the maximum depth of any bucket in
the hash table as well as a separate node for each bucket (or chain)
containing the current depth and maximum depth for that bucket.
2004-06-29 02:30:12 +00:00
John Baldwin
a5471e4ef4 Remove the signal_caught argument from sleepq_timedwait() as it was
effectively always zero.
2004-06-28 18:57:06 +00:00
Bruce Evans
a13ec35b05 Fixed some common printf format errors. Don't assume that "struct foo *"
is "void *" (it isn't) or that the default promotion of pid_t is int.
Instead, assume that casting "struct foo *" to "void *" and printing the
result with %p is useful, and that all pid_t's are representable as longs.

Fixed some minor style bugs (mainly spelling errors in comments).
2004-05-14 20:51:42 +00:00
John Baldwin
3335671ddd Split sleepq_wakeup_thread() into two functions. sleepq_remove_thread()
removes a specific thread from a sleep queue.  sleepq_resume_thread()
resumes scheduling of a thread that has been previously removed from a
sleep queue.
- sleepq_catch_signals() just removes a thread from the queue it was just
  added to when a pending signal is found.
- sleepq_signal() and sleepq_broadcast() remove threads from a queue,
  drop the queue lock, and then resume all the previously removed threads.
  This doesn't completely fix the sched_lock <-> sleepq chain LOR, but it
  makes it a little better as we no longer call setrunnble() with a sleep
  queue lock held meaning if setrunnable() tries to wakeup the swapper we
  don't try to lock two sleep queue chains at the same time.
2004-05-13 20:00:43 +00:00
Daniel Eischen
4fc21c0947 Keep track of threads waiting in kse_release() to avoid a race
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>
2004-04-28 20:36:53 +00:00
John Baldwin
27de234992 Remove a bogus assertion and readd it in a more correct location. A thread
might be enqueued on a sleep queue but not be asleep when the timeout fires
if it is blocked on a lock trying to check for pending signals before going
to sleep.  In the case of fixing up the TDF_TIMEOUT race, however, the
thread must be marked asleep.

Reported by:	kan (the bogus one)
2004-03-16 18:56:22 +00:00
John Baldwin
1ed3e44f22 - Remove old sleep queues.
- Remove sleepqueue argument from sleepq_set_timeout() since it is not
  used.
2004-03-12 19:06:18 +00:00
John Baldwin
efac7951fe Always assert that the passed in lock is the same as the saved lock in the
sleep queue now that the one abnormal case has been fixed.
2004-03-02 15:02:08 +00:00
John Baldwin
dd75b0a90d Add an implementation of a generic sleep queue abstraction that is used
to queue threads sleeping on a wait channel similar to how turnstiles are
used to queue threads waiting for a lock.  This subsystem will be used as
the backend for sleep/wakeup and condition variables initially.  Eventually
it will also be used to replace the ithread-specific iwait thread
inhibitor.

Sleep queues are also not locked by sched_lock, so this splits sched_lock
up a bit further increasing concurrency within the scheduler.  Sleep queues
also natively support timeouts on sleeps and interruptible sleeps allowing
for the reduction of a lot of duplicated code between the sleep/wakeup and
condition variable implementations.  For more details on the sleep queue
implementation, check the comments in sys/sleepqueue.h and
kern/subr_sleepqueue.c.
2004-02-27 18:33:09 +00:00