Commit Graph

239 Commits

Author SHA1 Message Date
Dmitry Chagin
fd07ddcf6f Add _NEW flag to mtx(9), sx(9), rmlock(9) and rwlock(9).
A _NEW flag passed to _init_flags() to avoid check for double-init.

Differential Revision:	https://reviews.freebsd.org/D1208
Reviewed by:	jhb, wblock
MFC after:	1 Month
2014-12-13 21:00:10 +00:00
Konstantin Belousov
6afb32fc67 Disable recursion for the process spinlock.
Tested by:	pho
Discussed with:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
2014-12-01 17:36:10 +00:00
Konstantin Belousov
5c7bebf961 The process spin lock currently has the following distinct uses:
- Threads lifetime cycle, in particular, counting of the threads in
  the process, and interlocking with process mutex and thread lock.
  The main reason of this is that turnstile locks are after thread
  locks, so you e.g. cannot unlock blockable mutex (think process
  mutex) while owning thread lock.

- Virtual and profiling itimers, since the timers activation is done
  from the clock interrupt context.  Replace the p_slock by p_itimmtx
  and PROC_ITIMLOCK().

- Profiling code (profil(2)), for similar reason.  Replace the p_slock
  by p_profmtx and PROC_PROFLOCK().

- Resource usage accounting.  Need for the spinlock there is subtle,
  my understanding is that spinlock blocks context switching for the
  current thread, which prevents td_runtime and similar fields from
  changing (updates are done at the mi_switch()).  Replace the p_slock
  by p_statmtx and PROC_STATLOCK().

The split is done mostly for code clarity, and should not affect
scalability.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
2014-11-26 14:10:00 +00:00
Warner Losh
40e6bdaf1e opt_global.h is included automatically in the build. No need to
explicitly include it in these places.

Sponsored by: Netflix
2014-11-18 17:06:56 +00:00
John Baldwin
2cba8dd301 Add a new thread state "spinning" to schedgraph and add tracepoints at the
start and stop of spinning waits in lock primitives.
2014-11-04 16:35:56 +00:00
Attilio Rao
54366c0bd7 - For kernel compiled only with KDTRACE_HOOKS and not any lock debugging
option, unbreak the lock tracing release semantic by embedding
  calls to LOCKSTAT_PROFILE_RELEASE_LOCK() direclty in the inlined
  version of the releasing functions for mutex, rwlock and sxlock.
  Failing to do so skips the lockstat_probe_func invokation for
  unlocking.
- As part of the LOCKSTAT support is inlined in mutex operation, for
  kernel compiled without lock debugging options, potentially every
  consumer must be compiled including opt_kdtrace.h.
  Fix this by moving KDTRACE_HOOKS into opt_global.h and remove the
  dependency by opt_kdtrace.h for all files, as now only KDTRACE_FRAMES
  is linked there and it is only used as a compile-time stub [0].

[0] immediately shows some new bug as DTRACE-derived support for debug
in sfxge is broken and it was never really tested.  As it was not
including correctly opt_kdtrace.h before it was never enabled so it
was kept broken for a while.  Fix this by using a protection stub,
leaving sfxge driver authors the responsibility for fixing it
appropriately [1].

Sponsored by:	EMC / Isilon storage division
Discussed with:	rstone
[0] Reported by:	rstone
[1] Discussed with:	philip
2013-11-25 07:38:45 +00:00
Davide Italiano
7faf4d90e8 Fix lc_lock/lc_unlock() support for rmlocks held in shared mode. With
current lock classes KPI it was really difficult because there was no
way to pass an rmtracker object to the lock/unlock routines. In order
to accomplish the task, modify the aforementioned functions so that
they can return (or pass as argument) an uinptr_t, which is in the rm
case used to hold a pointer to struct rm_priotracker for current
thread. As an added bonus, this fixes rm_sleep() in the rm shared
case, which right now can communicate priotracker structure between
lc_unlock()/lc_lock().

Suggested by:	jhb
Reviewed by:	jhb
Approved by:	re (delphij)
2013-09-20 23:06:21 +00:00
Attilio Rao
ac6b769be9 Give mutex(9) the ability to recurse on a per-instance basis.
Now the MTX_RECURSE flag can be passed to the mtx_*_flag() calls.
This helps in cases we want to narrow down to specific calls the
possibility to recurse for some locks.

Sponsored by:	EMC / Isilon storage division
Reviewed by:	jeff, alc
Tested by:	pho
2013-08-09 11:24:29 +00:00
Scott Long
de925dd31f Fix r253823. Some WIP patches snuck in.
Submitted by:	zont
2013-07-30 23:50:09 +00:00
Scott Long
fc4a5f052b Create a knob, kern.ipc.sfreadahead, that allows one to tune the amount of
readahead that sendfile() will do.  Default remains the same.

Obtained from:	Netflix
MFC after:	3 days
2013-07-30 23:26:05 +00:00
John Baldwin
b5fb43e572 A few mostly cosmetic nits to aid in debugging:
- Call lock_init() first before setting any lock_object fields in
  lock init routines.  This way if the machine panics due to a duplicate
  init the lock's original state is preserved.
- Somewhat similarly, don't decrement td_locks and td_slocks until after
  an unlock operation has completed successfully.
2013-06-25 20:23:08 +00:00
Attilio Rao
cd2fe4e632 Fixup r240424: On entering KDB backends, the hijacked thread to run
interrupt context can still be idlethread. At that point, without the
panic condition, it can still happen that idlethread then will try to
acquire some locks to carry on some operations.

Skip the idlethread check on block/sleep lock operations when KDB is
active.

Reported by:	jh
Tested by:	jh
MFC after:	1 week
2012-12-22 09:37:34 +00:00
Attilio Rao
7f44c61839 Give mtx(9) the ability to crunch different type of structures, with the
only constraint that they have a lock cookie named mtx_lock.
This name, then, becames reserved from the struct that wants to use the
mtx(9) KPI and other locking primitives cannot reuse it for their
members.

Namely such structs are the current struct mtx and the new
struct mtx_padalign.  The new structure will define an object which is
the same as the same layout of a struct mtx but will be allocated in
areas aligned to the cache line size and will be as big as a cache line.

This is supposed to give higher performance for highly contented mutexes
both spin or sleep (because of the adaptive spinning), where the cache
line contention results in too much traffic on the system bus.

The struct mtx_padalign can be used in a completely transparent way
with the mtx(9) KPI.

At the moment, a possibility to MFC the patch should be carefully
evaluated because this patch breaks the low level KPI
(not its representation though).

Discussed with:	jhb
Reviewed by:	jeff, andre
Reviewed by:	mdf (earlier version)
Tested by:	jimharris
2012-10-31 13:38:56 +00:00
Attilio Rao
0a15e5d30d Remove all the checks on curthread != NULL with the exception of some MD
trap checks (eg. printtrap()).

Generally this check is not needed anymore, as there is not a legitimate
case where curthread != NULL, after pcpu 0 area has been properly
initialized.

Reviewed by:	bde, jhb
MFC after:	1 week
2012-09-13 22:26:22 +00:00
Attilio Rao
e3ae0dfe69 Improve check coverage about idle threads.
Idle threads are not allowed to acquire any lock but spinlocks.
Deny any attempt to do so by panicing at the locking operation
when INVARIANTS is on. Then, remove the check on blocking on a
turnstile.
The check in sleepqueues is left because they are not allowed to use
tsleep() either which could happen still.

Reviewed by:	bde, jhb, kib
MFC after:	1 week
2012-09-12 22:10:53 +00:00
Fabien Thomas
f5f9340b98 Add software PMC support.
New kernel events can be added at various location for sampling or counting.
This will for example allow easy system profiling whatever the processor is
with known tools like pmcstat(8).

Simultaneous usage of software PMC and hardware PMC is possible, for example
looking at the lock acquire failure, page fault while sampling on
instructions.

Sponsored by: NETASQ
MFC after:	1 month
2012-03-28 20:58:30 +00:00
Andriy Gapon
353705930f panic: add a switch and infrastructure for stopping other CPUs in SMP case
Historical behavior of letting other CPUs merily go on is a default for
time being.  The new behavior can be switched on via
kern.stop_scheduler_on_panic tunable and sysctl.

Stopping of the CPUs has (at least) the following benefits:
- more of the system state at panic time is preserved intact
- threads and interrupts do not interfere with dumping of the system
  state

Only one thread runs uninterrupted after panic if stop_scheduler_on_panic
is set.  That thread might call code that is also used in normal context
and that code might use locks to prevent concurrent execution of certain
parts.  Those locks might be held by the stopped threads and would never
be released.  To work around this issue, it was decided that instead of
explicit checks for panic context, we would rather put those checks
inside the locking primitives.

This change has substantial portions written and re-written by attilio
and kib at various times.  Other changes are heavily based on the ideas
and patches submitted by jhb and mdf.  bde has provided many insights
into the details and history of the current code.

The new behavior may cause problems for systems that use a USB keyboard
for interfacing with system console.  This is because of some unusual
locking patterns in the ukbd code which have to be used because on one
hand ukbd is below syscons, but on the other hand it has to interface
with other usb code that uses regular mutexes/Giant for its concurrency
protection.  Dumping to USB-connected disks may also be affected.

PR:			amd64/139614 (at least)
In cooperation with:	attilio, jhb, kib, mdf
Discussed with:		arch@, bde
Tested by:		Eugene Grosbein <eugen@grosbein.net>,
			gnn,
			Steven Hartland <killing@multiplay.co.uk>,
			glebius,
			Andrew Boyer <aboyer@averesystems.com>
			(various versions of the patch)
MFC after:		3 months (or never)
2011-12-11 21:02:01 +00:00
Attilio Rao
ccdf233323 Introduce macro stubs in the mutex implementation that will be always
defined and will allow consumers, willing to provide options, file and
line to locking requests, to not worry about options redefining the
interfaces.
This is typically useful when there is the need to build another
locking interface on top of the mutex one.

The introduced functions that consumers can use are:
- mtx_lock_flags_
- mtx_unlock_flags_
- mtx_lock_spin_flags_
- mtx_unlock_spin_flags_
- mtx_assert_
- thread_lock_flags_

Spare notes:
- Likely we can get rid of all the 'INVARIANTS' specification in the
  ppbus code by using the same macro as done in this patch (but this is
  left to the ppbus maintainer)
- all the other locking interfaces may require a similar cleanup, where
  the most notable case is sx which will allow a further cleanup of
  vm_map locking facilities
- The patch should be fully compatible with older branches, thus a MFC
  is previewed (infact it uses all the underlying mechanisms already
  present).

Comments review by:	eadler, Ben Kaduk
Discussed with:		kib, jhb
MFC after:	1 month
2011-11-20 16:33:09 +00:00
Pawel Jakub Dawidek
d576deedb5 Constify arguments for locking KPIs where possible.
This enables locking consumers to pass their own structures around as const and
be able to assert locks embedded into those structures.

Reviewed by:	ed, kib, jhb
2011-11-16 21:51:17 +00:00
John Baldwin
961135ead8 - Remove <machine/mutex.h>. Most of the headers were empty, and the
contents of the ones that were not empty were stale and unused.
- Now that <machine/mutex.h> no longer exists, there is no need to allow it
  to override various helper macros in <sys/mutex.h>.
- Rename various helper macros for low-level operations on mutexes to live
  in the _mtx_* or __mtx_* namespaces.  While here, change the names to more
  closely match the real API functions they are backing.
- Drop support for including <sys/mutex.h> in assembly source files.

Suggested by:	bde (1, 2)
2010-11-09 20:46:41 +00:00
Attilio Rao
98332c8c71 Right now, WITNESS just blindly pipes all the output to the
(TOCONS | TOLOG) mask even when called from DDB points.
That breaks several output, where the most notable is textdump output.
Fix this by having configurable callbacks passed to witness_list_locks()
and witness_display_spinlock() for printing out datas.

Reported by:	several broken textdump outputs
Tested by:	Giovanni Trematerra
		<giovanni dot trematerra at gmail dot com>
MFC after:	7 days
X-MFC:		r207922
2010-05-11 18:24:22 +00:00
Attilio Rao
b0b9dee5c9 - Fix a race in sched_switch() of sched_4bsd.
In the case of the thread being on a sleepqueue or a turnstile, the
  sched_lock was acquired (without the aid of the td_lock interface) and
  the td_lock was dropped. This was going to break locking rules on other
  threads willing to access to the thread (via the td_lock interface) and
  modify his flags (allowed as long as the container lock was different
  by the one used in sched_switch).
  In order to prevent this situation, while sched_lock is acquired there
  the td_lock gets blocked. [0]
- Merge the ULE's internal function thread_block_switch() into the global
  thread_lock_block() and make the former semantic as the default for
  thread_lock_block(). This means that thread_lock_block() will not
  disable interrupts when called (and consequently thread_unlock_block()
  will not re-enabled them when called). This should be done manually
  when necessary.
  Note, however, that ULE's thread_unblock_switch() is not reaped
  because it does reflect a difference in semantic due in ULE (the
  td_lock may not be necessarilly still blocked_lock when calling this).
  While asymmetric, it does describe a remarkable difference in semantic
  that is good to keep in mind.

[0] Reported by:	Kohji Okuno
			<okuno dot kohji at jp dot panasonic dot com>
Tested by:		Giovanni Trematerra
			<giovanni dot trematerra at gmail dot com>
MFC:			2 weeks
2010-01-23 15:54:21 +00:00
Poul-Henning Kamp
6778431478 Revert previous commit and add myself to the list of people who should
know better than to commit with a cat in the area.
2009-09-08 13:19:05 +00:00
Poul-Henning Kamp
b34421bf9c Add necessary include. 2009-09-08 13:16:55 +00:00
Attilio Rao
353998acc3 * Change the scope of the ASSERT_ATOMIC_LOAD() from a generic check to
a pointer-fetching specific operation check. Consequently, rename the
  operation ASSERT_ATOMIC_LOAD_PTR().
* Fix the implementation of ASSERT_ATOMIC_LOAD_PTR() by checking
  directly alignment on the word boundry, for all the given specific
  architectures. That's a bit too strict for some common case, but it
  assures safety.
* Add a comment explaining the scope of the macro
* Add a new stub in the lockmgr specific implementation

Tested by: marcel (initial version), marius
Reviewed by: rwatson, jhb (comment specific review)
Approved by: re (kib)
2009-08-17 16:17:21 +00:00
Bjoern A. Zeeb
8d518523cc Add a new macro to test that a variable could be loaded atomically.
Check that the given variable is at most uintptr_t in size and that
it is aligned.

Note: ASSERT_ATOMIC_LOAD() uses ALIGN() to check for adequate
      alignment -- however, the function of ALIGN() is to guarantee
      alignment, and therefore may lead to stronger alignment
      enforcement than necessary for types that are smaller than
      sizeof(uintptr_t).

Add checks to mtx, rw and sx locks init functions to detect possible
breakage. This was used during debugging of the problem fixed with
r196118 where a pointer was on an un-aligned address in the dpcpu area.

In collaboration with:	rwatson
Reviewed by:		rwatson
Approved by:		re (kib)
2009-08-14 21:46:54 +00:00
John Baldwin
a571ad41ae Remove extra cpu_spinwait() invocations. This should really only be used
in tight spin loops, not in these edge cases where we restart a much
larger loop only a few times.

Reviewed by:	attilio
2009-05-29 14:03:34 +00:00
John Baldwin
fa29f0236f Tweak a few comments on adaptive spinning. 2009-05-29 13:56:34 +00:00
Stacey Son
a5aedd68b4 Add the OpenSolaris dtrace lockstat provider. The lockstat provider
adds probes for mutexes, reader/writer and shared/exclusive locks to
gather contention statistics and other locking information for
dtrace scripts, the lockstat(1M) command and other potential
consumers.

Reviewed by:	attilio jhb jb
Approved by:	gnn (mentor)
2009-05-26 20:28:22 +00:00
John Baldwin
583220dc4c Remove an obsolete assertion. We always wake up all waiters when unlocking
a mutex and never set the lock cookie == MTX_CONTESTED.
2009-05-20 18:29:14 +00:00
Jeff Roberson
1723a06485 - Wrap lock profiling state variables in #ifdef LOCK_PROFILING blocks. 2009-03-15 08:03:54 +00:00
Jeff Roberson
d3df4af368 - When a mutex is destroyed while locked we need to inform lock profiling
that it has been released.
2009-03-14 11:43:38 +00:00
John Baldwin
413134305e Teach WITNESS about the interlocks used with lockmgr. This removes a bunch
of spurious witness warnings since lockmgr grew witness support.  Before
this, every time you passed an interlock to a lockmgr lock WITNESS treated
it as a LOR.

Reviewed by:	attilio
2008-09-10 19:13:30 +00:00
John Baldwin
bf9c6c31e7 Various whitespace fixes. 2008-09-10 17:59:21 +00:00
John Baldwin
ad69e26b69 Add KASSERT()'s to catch attempts to recurse on spin mutexes that aren't
marked recursable either via mtx_lock_spin() or thread_lock().

MFC after:	1 week
2008-02-13 23:39:05 +00:00
John Baldwin
13c85a48df Add a couple of assertions and KTR logging to thread_lock_flags() to
match mtx_lock_spin_flags().

MFC after:	1 week
2008-02-13 23:33:50 +00:00
Jeff Roberson
eea4f254fe - Re-implement lock profiling in such a way that it no longer breaks
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
2007-12-15 23:13:31 +00:00
Attilio Rao
573c6b82df Make ADAPTIVE_GIANT as the default in the kernel and remove the option.
Currently, Giant is not too much contented so that it is ok to treact it
like any other mutexes.

Please don't forget to update your own custom config kernel files.

Approved by:	cognet, marcel (maintainers of arches where option is
		not enabled at the moment)
2007-11-28 05:50:45 +00:00
Attilio Rao
49aead8a10 Simplify the adaptive spinning algorithm in rwlock and mutex:
currently, before to spin the turnstile spinlock is acquired and the
waiters flag is set.
This is not strictly necessary, so just spin before to acquire the
spinlock and to set the flags.
This will simplify a lot other functions too, as now we have the waiters
flag set only if there are actually waiters.
This should make wakeup/sleeping couplet faster under intensive mutex
workload.
This also fixes a bug in rw_try_upgrade() in the adaptive case, where
turnstile_lookup() will recurse on the ts_lock lock that will never be
really released [1].

[1] Reported by: jeff with Nokia help
Tested by: pho, kris (earlier, bugged version of rwlock part)
Discussed with: jhb [2], jeff
MFC after: 1 week

[2] John had a similar patch about 6.x and/or 7.x about mutexes probabilly
2007-11-26 22:37:35 +00:00
Attilio Rao
f9721b43ed Expand lock class with the "virtual" function lc_assert which will offer
an unified way for all the lock primitives to express lock assertions.
Currenty, lockmgrs and rmlocks don't have assertions, so just panic in
that case.
This will be a base for more callout improvements.

Ok'ed by: jhb, jeff
2007-11-18 14:43:53 +00:00
Julian Elischer
431f890614 generally we are interested in what thread did something as
opposed to what process. Since threads by default have teh name of the
process unless over-written with more useful information, just print the
thread name instead.
2007-11-14 06:21:24 +00:00
Jeff Roberson
6ea38de8aa - Remove the global definition of sched_lock in mutex.h to break
new code and third party modules which try to depend on it.
 - Initialize sched_lock in sched_4bsd.c.
 - Declare sched_lock in sparc64 pmap.c and assert that we're compiling
   with SCHED_4BSD to prevent accidental crashes from running ULE.  This
   is the sole remaining file outside of the scheduler that uses the
   global sched_lock.

Approved by:	re
2007-07-18 20:46:06 +00:00
Jeff Roberson
773890b9a8 - Add the proper lock profiling calls to _thread_lock().
Obtained from:	kipmacy
Approved by:	re
2007-07-18 20:38:13 +00:00
Matt Jacob
65d32cd8fb Propagate volatile qualifier to make gcc4.2 happy. 2007-06-09 18:09:37 +00:00
Attilio Rao
e682569165 Remove the MUTEX_WAKE_ALL option and make it the default behaviour for our
mutexes.
Currently we alredy force MUTEX_WAKE_ALL beacause of some problems with the
!MUTEX_WAKE_ALL case (unavioidable priority inversion).
2007-06-08 21:36:52 +00:00
Jeff Roberson
710eacdc5f - Placing the 'volatile' on the right side of the * in the td_lock
declaration removes the need for __DEVOLATILE().

Pointed out by:	tegge
2007-06-06 03:40:47 +00:00
Attilio Rao
d301eb10c7 Fix a problem with not-preemptive kernels caming from mis-merging of
existing code with the new thread_lock patch.
This also cleans up a bit unlock operation for mutexes.

Approved by: jhb, jeff(mentor)
2007-06-05 18:57:09 +00:00
Konstantin Belousov
b95b98b0bd Restore non-SMP build.
Reviewed by:	attilio
2007-06-05 14:20:13 +00:00
Jeff Roberson
2502c107ba Commit 3/14 of sched_lock decomposition.
- Add a per-turnstile spinlock to solve potential priority propagation
   deadlocks that are possible with thread_lock().
 - The turnstile lock order is defined as the exact opposite of the
   lock order used with the sleep locks they represent.  This allows us
   to walk in reverse order in priority_propagate and this is the only
   place we wish to multiply acquire turnstile locks.
 - Use the turnstile_chain lock to protect assigning mutexes to turnstiles.
 - Change the turnstile interface to pass back turnstile pointers to the
   consumers.  This allows us to reduce some locking and makes it easier
   to cancel turnstile assignment while the turnstile chain lock is held.

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)
2007-06-04 23:51:44 +00:00
John Baldwin
c91fcee75d Move lock_profile_object_{init,destroy}() into lock_{init,destroy}(). 2007-05-18 15:04:59 +00:00