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* Add a reset sysctl for mutex profiling: zeros all of the mutexrwatson2004-01-281-0/+27
| | | | | | | | profiling buffers and hash table. This makes it a lot easier to do multiple profiling runs without rebooting or performing gratuitous arithmetic. Sysctl is named debug.mutex.prof.reset. Reviewed by: jake
* Rework witness_lock() to make it slightly more useful and flexible.jhb2004-01-281-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | - witness_lock() is split into two pieces: witness_checkorder() and witness_lock(). Witness_checkorder() determines if acquiring a specified lock at the time it is called would result in a lock order. It optionally adds a new lock order relationship as well. witness_lock() updates witness's data structures to assume that a lock has been acquired by stick a new lock instance in the appropriate lock instance list. - The mutex and sx lock functions now call checkorder() prior to trying to acquire a lock and continue to call witness_lock() after the acquire is completed. This will let witness catch a deadlock before it happens rather than trying to do so after the threads have deadlocked (i.e. never actually report it). - A new function witness_defineorder() has been added that adds a lock order between two locks at runtime without having to acquire the locks. If the lock order cannot be added it will return an error. This function is available to programmers via the WITNESS_DEFINEORDER() macro which accepts either two mutexes or two sx locks as its arguments. - A few simple wrapper macros were added to allow developers to call witness_checkorder() anywhere as a way of enforcing locking assertions in code that might acquire a certain lock in some situations. The macros are: witness_check_{mutex,shared_sx,exclusive_sx} and take an appropriate lock as the sole argument. - The code to remove a lock instance from a lock list in witness_unlock() was unnested by using a goto to vastly improve the readability of this function.
* - Add a flags parameter to mi_switch. The value of flags may be SW_VOL orjeff2004-01-251-2/+1
| | | | | | | | | | SW_INVOL. Assert that one of these is set in mi_switch() and propery adjust the rusage statistics. This is to simplify the large number of users of this interface which were previously all required to adjust the proper counter prior to calling mi_switch(). This also facilitates more switch and locking optimizations. - Change all callers of mi_switch() to pass the appropriate paramter and remove direct references to the process statistics.
* Add some basic support for measuring sleep mutex contention to therwatson2004-01-251-5/+33
| | | | | | | | | | | | | | | | | | | | | | mutex profiling code. As with existing mutex profiling, measurement is done with respect to mtx_lock() instances in the code, as opposed to specific mutexes. In particular, measure two things: (1) Lock contention. How often did this mtx_lock() call get made and have to sleep (or almost sleep) waiting for the lock. This helps identify the "victims" of contention. (2) Hold contention. How often, while the lock was held by a thread as a result of this mtx_lock(), did another thread try to acquire the same mutex. This helps identify the causes of contention. I'm currently exploring adding measurement of "time waited for the lock", but the current implementation has proven useful to me so far so I figured I'd commit it so others could try it out. Note that this increases the size of mutexes when MUTEX_PROFILING is enabled, so you might find you need to further bump UMA_BOOT_PAGES. Fixes welcome. The once over: des, others
* - Allow mtx_trylock() to recurse on a recursive mutex. Attempts to recursejhb2004-01-051-5/+11
| | | | | | | | on a non-recursive mutex will fail but will not trigger any assertions. - Add an assertion to mtx_lock() that one never recurses on a non-recursive mutex. This is mostly useful for the non-WITNESS case. Requested by: deischen, julian, others (1)
* Add an implementation of turnstiles and change the sleep mutex code to usejhb2003-11-111-225/+39
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | turnstiles to implement blocking isntead of implementing a thread queue directly. These turnstiles are somewhat similar to those used in Solaris 7 as described in Solaris Internals but are also different. Turnstiles do not come out of a fixed-sized pool. Rather, each thread is assigned a turnstile when it is created that it frees when it is destroyed. When a thread blocks on a lock, it donates its turnstile to that lock to serve as queue of blocked threads. The queue associated with a given lock is found by a lookup in a simple hash table. The turnstile itself is protected by a lock associated with its entry in the hash table. This means that sched_lock is no longer needed to contest on a mutex. Instead, sched_lock is only used when manipulating run queues or thread priorities. Turnstiles also implement priority propagation inherently. Currently turnstiles only support mutexes. Eventually, however, turnstiles may grow two queue's to support a non-sleepable reader/writer lock implementation. For more details, see the comments in sys/turnstile.h and kern/subr_turnstile.c. The two primary advantages from the turnstile code include: 1) the size of struct mutex shrinks by four pointers as it no longer stores the thread queue linkages directly, and 2) less contention on sched_lock in SMP systems including the ability for multiple CPUs to contend on different locks simultaneously (not that this last detail is necessarily that much of a big win). Note that 1) means that this commit is a kernel ABI breaker, so don't mix old modules with a new kernel and vice versa. Tested on: i386 SMP, sparc64 SMP, alpha SMP
* If a spin lock is held for too long and WITNESS is enabled, then calljhb2003-07-311-3/+9
| | | | | witness_display_spinlock() to see if we can find out where the current owner of the spin lock last acquired the lock.
* When complaining about a sleeping thread owning a mutex, display thejhb2003-07-301-1/+3
| | | | | | | thread's pid to make debugging easier for people who don't want to have to use the intended tool for these panics (witness). Indirectly prodded by: kris
* - Add comments about the maintenance of the per-thread list of contestedjhb2003-07-021-4/+9
| | | | | | | | | | | | | 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)
* Use __FBSDID().obrien2003-06-111-1/+3
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* Add "" around mutex name to make message less confusing.phk2003-05-311-1/+1
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* Use TD_IS_RUNNING() instead of thread_running() in the adaptive mutexjhb2003-04-171-7/+2
| | | | code.
* Move the _oncpu entry from the KSE to the thread.julian2003-04-101-1/+2
| | | | | The entry in the KSE still exists but it's purpose will change a bit when we add the ability to lock a KSE to a cpu.
* Remove unused mtx_lock_giant(), mtx_unlock_giant(), related globalstjr2003-03-231-43/+0
| | | | and sysctls.
* Including <sys/stdint.h> is (almost?) universally only to be able to usephk2003-03-181-1/+0
| | | | | %j in printfs, so put a newsted include in <sys/systm.h> where the printf prototype lives and save everybody else the trouble.
* Axe the useless MTX_SLEEPABLE flag. mutexes are not sleepable locks.jhb2003-03-111-3/+1
| | | | | Nothing used this flag and WITNESS would have panic'd during mtx_init() if anything had.
* Remove safety belt: it is now ok to do a mtx_trylock() on a mutex youjhb2003-03-041-5/+4
| | | | | | | already own. The mtx_trylock() will fail however. Enhance the comment at the top of the try lock function to explain this. Requested by: jlemon and his evil netisr locking
* Miscellaneous cleanups to _mtx_lock_sleep():jhb2003-03-041-4/+6
| | | | | | | | - Declare some local variables at the top of the function instead of in a nested block. - Use mtx_owned() instead of masking off bits from mtx_lock manually. - Read the value of mtx_lock into 'v' as a separate line rather than inside an if statement for clarity. This code is hairy enough as it is.
* Properly assert that mtx_trylock() is not called on a mutex we alreadyjhb2003-03-041-8/+4
| | | | | | | owned. Previously the KASSERT would only trigger if we successfully acquired a lock that we already held. However, _obtain_lock() fails to acquire locks that we already hold, so the KASSERT was never checked in the case it was supposed to fail.
* Unbreak mutex profiling (at least for me).mtm2003-02-251-3/+15
| | | | | | | | | | o Always check for null when dereferencing the filename component. o Implement a try-and-backoff method for allocating memory to dump stats to avoid a spin-lock -> sleep-lock mutex lock order panic with WITNESS. Approved by: des, markm (mentor) Not objected: jhb
* There's absolutely no need for a struct-within-a-struct, so move thedes2003-01-211-14/+12
| | | | counters out of the inner struct and remove it.
* Disable the kernacc() check in mtx_validate() until such time that kernaccphk2002-10-251-0/+5
| | | | | | | | | does not require Giant. This means that we may miss panics on a class of mutex programming bugs, but only if running with a Chernobyl setting of debug-flags. Spotted by: Pete Carah <pete@ns.altadena.net>
* Whitespace cleanup.des2002-10-231-10/+9
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* Change the `mutex_prof' structure to use three variables containedrobert2002-10-221-18/+14
| | | | | | in an anonymous structure as counters, instead of an array with preprocessor-defined names for indices. Remove the associated XXX- comment.
* Reduce the overhead of the mutex statistics gathering code, try to producedes2002-10-211-19/+28
| | | | shorter lines in the report, and clean up some minor style issues.
* - Create a new scheduler api that is defined in sys/sched.hjeff2002-10-121-4/+2
| | | | | | | | | | - Begin moving scheduler specific functionality into sched_4bsd.c - Replace direct manipulation of scheduler data with hooks provided by the new api. - Remove KSE specific state modifications and single runq assumptions from kern_switch.c Reviewed by: -arch
* Rename the mutex thread and process states to use a more generic 'LOCK'jhb2002-10-021-13/+13
| | | | | | | | | name instead. (e.g., SLOCK instead of SMTX, TD_ON_LOCK() instead of TD_ON_MUTEX()) Eventually a turnstile abstraction will be added that will be shared with mutexes and other types of locks. SLOCK/TDI_LOCK will be used internally by the turnstile code and will not be specific to mutexes. Making the change now ensures that turnstiles can be dropped in at a later date without affecting the ABI of userland applications.
* uh, commit all of the patchjulian2002-09-291-0/+1
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* commit the version I actually tested..julian2002-09-291-2/+4
| | | | Submitted by: davidxu
* Implement basic KSE loaning. This stops a hread that is blocked in BOUND modejulian2002-09-291-1/+2
| | | | | | | | | from stopping another thread from completing a syscall, and this allows it to release its resources etc. Probably more related commits to follow (at least one I know of) Initial concept by: julian, dillon Submitted by: davidxu
* Completely redo thread states.julian2002-09-111-7/+6
| | | | Reviewed by: davidxu@freebsd.org
* Add some KASSERT()'s to ensure that we don't perform spin mutex ops onjhb2002-09-031-4/+16
| | | | | | sleep mutexes and vice versa. WITNESS normally should catch this but not everyone uses WITNESS so this is a fallback to catch nasty but easy to do bugs.
* Add a new KTR type KTR_CONTENTION, and use it in the mutex code toiedowse2002-08-261-0/+20
| | | | | | | | log the start and end of periods during which mtx_lock() is waiting to acquire a sleep mutex. The log message includes the file and line of both the waiter and the holder. Reviewed by: jhb, jake
* Disable optimization of spinlocks on UP kernels w/o debugging for nowjhb2002-07-271-2/+2
| | | | | | | | since it breaks mtx_owned() on spin mutexes when used outside of mtx_assert(). Unfortunately we currently use it in the i386 MD code and in the sio(4) driver. Reported by: bde
* Add mtx_ prefixes to the fields used for mutex profiling, and fix a bugdes2002-07-031-11/+12
| | | | | | | where the profiling code would report the release point instead of the acquisition point. Requested by: bde
* Part 1 of KSE-IIIjulian2002-06-291-15/+16
| | | | | | | | | | | | | The ability to schedule multiple threads per process (one one cpu) by making ALL system calls optionally asynchronous. to come: ia64 and power-pc patches, patches for gdb, test program (in tools) Reviewed by: Almost everyone who counts (at various times, peter, jhb, matt, alfred, mini, bernd, and a cast of thousands) NOTE: this is still Beta code, and contains lots of debugging stuff. expect slight instability in signals..
* Replace thread_runnable() with thread_running() as the latter is morejhb2002-06-041-6/+5
| | | | | | accurate. Suggested by: julian
* Optimize the adaptive mutex spin a bit. Use a simple while loop withjhb2002-06-041-1/+4
| | | | | | | | | simple reads (and on IA32, a "pause" instruction for each interation of the loop) to spin until either the mutex owner field changes, or the lock owner stops executing. Suggested by: tanimura Tested on: i386
* Add a private thread_runnable() macro to make the code more readable andjhb2002-06-041-3/+5
| | | | make the KSE diff easier to maintain.
* Make the counters uintmax_ts, and use %ju rather than %llu.des2002-05-231-2/+3
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* Rename pause() to ia32_pause() so it doesn't conflict with the pause()jhb2002-05-221-5/+5
| | | | | function defined in <unistd.h>. I didn't #ifdef _KERNEL it because the mutex implementation in libpthread will probably need this.
* Rename cpu_pause() to pause(). Originally I was going to make this anjhb2002-05-221-5/+5
| | | | | | | | | MI API with empty cpu_pause() functions on other arch's, but this functionality is definitely unique to IA-32, so I decided to leave it as i386-only and wrap it in #ifdef's. I should have dropped the cpu_ prefix when I made that decision. Requested by: bde
* Add appropriate IA32 "pause" instructions to improve performanec onjhb2002-05-211-1/+17
| | | | | | Pentium 4's and newer IA32 processors. The "pause" instruction has been verified by Intel to be a NOP on all currently existing IA32 processors prior to the Pentium 4.
* Fix an old cut 'n' paste bug inherited from BSD/OS: don't increment 'i'jhb2002-05-211-1/+1
| | | | twice once we are in the long wait stage of spinning on a spin mutex.
* Whitespace fixup, properly indent the body of an else clause.jhb2002-05-211-2/+2
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* Add code to make default mutexes adaptive if the ADAPTIVE_MUTEXES kerneljhb2002-05-211-0/+26
| | | | | | | | | | | | | | | | | | | | | | option is used (not on by default). - In the case of trying to lock a mutex, if the MTX_CONTESTED flag is set, then we can safely read the thread pointer from the mtx_lock member while holding sched_lock. We then examine the thread to see if it is currently executing on another CPU. If it is, then we keep looping instead of blocking. - In the case of trying to unlock a mutex, it is now possible for a mutex to have MTX_CONTESTED set in mtx_lock but to not have any threads actually blocked on it, so we need to handle that case. In that case, we just release the lock as if MTX_CONTESTED was not set and return. - We do not adaptively spin on Giant as Giant is held for long times and it slows SMP systems down to a crawl (it was taking several minutes, like 5-10 or so for my test alpha and sparc64 SMP boxes to boot up when they adaptively spinned on Giant). - We only compile in the code to do this for SMP kernels, it doesn't make sense for UP kernels. Tested on: i386, alpha, sparc64
* Optimize spin mutexes for UP kernels without debugging to just enter andjhb2002-05-211-0/+8
| | | | | exit critical sections. We only contest on a spin mutex on an SMP kernel running on an SMP machine.
* Change mtx_init() to now take an extra argument. The third argument isjhb2002-04-041-8/+11
| | | | | | the generic lock type for use with witness. If this argument is NULL then the lock name is used as the lock type. Add a macro for a lock type name for network driver locks.
* Revert to open hashing. It makes the code simpler, and works farily welldes2002-04-021-16/+10
| | | | | | | even when the number of records approaches the size of the hash table. Besides, the previous implementation (using linear probing) was broken :) Also, use the newly introduced MTX_SYSINIT.
* - Move the MI mutexes sched_lock and Giant from being declared in thejhb2002-04-021-0/+27
| | | | | | | | | | various machdep.c's to being declared in kern_mutex.c. - Add a new function mutex_init() used to perform early initialization needed for mutexes such as setting up thread0's contested lock list and initializing MI mutexes. Change the various MD startup routines to call this function instead of duplicating all the code themselves. Tested on: alpha, i386
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