Commit Graph

30 Commits

Author SHA1 Message Date
John Baldwin
462a7add8e Add a new 'show sleepchain' ddb command similar to 'show lockchain' except
that it operates on lockmgr and sx locks.  This can be useful for tracking
down vnode deadlocks in VFS for example.  Note that this command is a bit
more fragile than 'show lockchain' as we have to poke around at the
wait channel of a thread to see if it points to either a struct lock or
a condition variable inside of a struct sx.  If td_wchan points to
something unmapped, then this command will terminate early due to a fault,
but no harm will be done.
2006-08-15 18:29:01 +00:00
John Baldwin
764e4d54e9 Adjust td_locks for non-spin mutexes, rwlocks, and sx locks so that it is
a count of all non-spin locks, not just lockmgr locks.  This can give us a
much cheaper way to see if we have any locks held (such as when returning
to userland via userret()) without requiring WITNESS.

MFC after:	1 week
2006-07-27 21:45:55 +00:00
John Baldwin
83a81bcb14 Add a new file (kern/subr_lock.c) for holding code related to struct
lock_obj objects:
- Add new lock_init() and lock_destroy() functions to setup and teardown
  lock_object objects including KTR logging and registering with WITNESS.
- Move all the handling of LO_INITIALIZED out of witness and the various
  lock init functions into lock_init() and lock_destroy().
- Remove the constants for static indices into the lock_classes[] array
  and change the code outside of subr_lock.c to use LOCK_CLASS to compare
  against a known lock class.
- Move the 'show lock' ddb function and lock_classes[] array out of
  kern_mutex.c over to subr_lock.c.
2006-01-17 16:55:17 +00:00
John Baldwin
3c6decc327 Trim another pointer from struct lock_object (and thus from struct mtx and
struct sx).  Instead of storing a direct pointer to a our lock_class
struct in lock_object, reserve 4 bits in the lo_flags field to serve as an
index into a global lock_classes array that contains pointers to the lock
classes.  Only debugging code such as WITNESS or INVARIANTS checks and KTR
logging need to access the lock_class member, so this shouldn't add any
overhead to production kernels.  It might add some slight overhead to
kernels using those debug options however.

As with the previous set of changes to lock_object, this is going to
completely obliterate the kernel ABI, so be sure to recompile all your
modules.
2006-01-06 18:07:32 +00:00
John Baldwin
d272fe53a4 Add a new 'show lock' command to ddb. If the argument has a valid lock
class, then it displays various information about the lock and calls a
new function pointer in lock_class (lc_ddb_show) to dump class-specific
information about the lock as well (such as the owner of a mutex or
xlock'ed sx lock).  This is easier than staring at hex dumps of locks to
figure out who owns the lock, etc.  Note that extending lock_class doesn't
affect the ABI for any kernel modules as the only code that deals with
lock_class structures directly is kern_mutex.c, kern_sx.c, and witness.

MFC after:	1 week
2005-12-13 23:14:35 +00:00
Warner Losh
9454b2d864 /* -> /*- for copyright notices, minor format tweaks as necessary 2005-01-06 23:35:40 +00:00
John Baldwin
03129ba97f Fix _sx_assert() to panic() rather than printf() when an assertion fails
and ignore assertions if we have already paniced.
2004-02-27 16:13:44 +00:00
Pawel Jakub Dawidek
f6739b1ddc Simplify check. We are only able to check exclusive lock and if
2nd condition is true, first one is true for sure.

Approved by:	jhb, scottl (mentor)
2004-02-19 14:19:31 +00:00
Pawel Jakub Dawidek
19b0efd32d Allow assert that the current thread does not hold the sx(9) lock.
Reviewed by:		jhb
In cooperation with:	juli, jhb
Approved by:		jhb, scottl (mentor)
2004-02-04 08:14:58 +00:00
John Baldwin
8d768e7676 Rework witness_lock() to make it slightly more useful and flexible.
- 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.
2004-01-28 20:39:57 +00:00
Don Lewis
857d9c60d0 Extend the mutex pool implementation to permit the creation and use of
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
2003-07-13 01:22:21 +00:00
David E. O'Brien
677b542ea2 Use __FBSDID(). 2003-06-11 00:56:59 +00:00
John Baldwin
9939f0f11c Set the lock type equal to the lock name for now as all of the current
sx locks don't use very specific lock names.
2002-04-04 20:49:35 +00:00
Andrew R. Reiter
c27b56999e - Add MTX_SYSINIT and SX_SYSINIT as macro glue for allowing sx and mtx
locks to be able to setup a SYSINIT call.  This helps in places where
  a lock is needed to protect some data, but the data is not truly
  associated with a subsystem that can properly initialize it's lock.
  The macros use the mtx_sysinit() and sx_sysinit() functions,
  respectively, as the handler argument to SYSINIT().

Reviewed by: alfred, jhb, smp@
2002-04-02 16:05:43 +00:00
Seigo Tanimura
98bf25aae1 Invert the test of sx_xholder for SX_LOCKED. We need to warn if a
thread other than the curthread holds an sx.

While I am here, break a line at the end of warning.
2002-01-18 09:21:15 +00:00
David E. O'Brien
a48740b6c5 Update to C99, s/__FUNCTION__/__func__/. 2001-12-10 05:51:45 +00:00
Matthew Dillon
f286003909 Create a mutex pool API for short term leaf mutexes.
Replace the manual mutex pool in kern_lock.c (lockmgr locks) with the new API.
Replace the mutexes embedded in sxlocks with the new API.
2001-11-13 21:55:13 +00:00
John Baldwin
781a35df6b Fix this to actually compile in the !INVARIANTS case.
Reported by:	Maxime Henrion <mux@qualys.com>
2001-10-24 14:18:33 +00:00
John Baldwin
4e5e677bc0 Change the sx(9) assertion API to use a sx_assert() function similar to
mtx_assert(9) rather than several SX_ASSERT_* macros.
2001-10-23 22:39:11 +00:00
John Baldwin
7ada587697 The mtx_init() and sx_init() functions bzero'd locks before handing them
off to witness_init() making the check for double intializating a lock by
testing the LO_INITIALIZED flag moot.  Workaround this by checking the
LO_INITIALIZED flag ourself before we bzero the lock structure.
2001-10-20 01:22:42 +00:00
Julian Elischer
b40ce4165d KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after:    ha ha ha ha
2001-09-12 08:38:13 +00:00
John Baldwin
b0b7cb508c Use witness_upgrade/downgrade for sx_try_upgrade/downgrade. 2001-08-23 22:51:22 +00:00
John Baldwin
e2870579fa Clear the sx_xholder pointer when downgrading an exclusive lock. 2001-08-23 17:57:37 +00:00
Jason Evans
d55229b72e Add sx_try_upgrade() and sx_downgrade().
Submitted by:	Alexander Kabaev <ak03@gte.com>
2001-08-13 21:25:30 +00:00
John Baldwin
5f36700a32 - Add trylock variants of shared and exclusive locks.
- The sx assertions don't actually need the internal sx mutex lock, so
  don't bother doing so.
- Add a new assertion SX_ASSERT_LOCKED() that asserts that either a
  shared or exclusive lock should be held.  This assertion should be used
  instead of SX_ASSERT_SLOCKED() in almost all cases.
- Adjust some KASSERT()'s to include file and line information.
- Use the new witness_assert() function in the WITNESS case for sx slock
  asserts to verify that the current thread actually owns a slock.
2001-06-27 06:39:37 +00:00
John Baldwin
2d96f0b145 - Move state about lock objects out of struct lock_object and into a new
struct lock_instance that is stored in the per-process and per-CPU lock
  lists.  Previously, the lock lists just kept a pointer to each lock held.
  That pointer is now replaced by a lock instance which contains a pointer
  to the lock object, the file and line of the last acquisition of a lock,
  and various flags about a lock including its recursion count.
- If we sleep while holding a sleepable lock, then mark that lock instance
  as having slept and ignore any lock order violations that occur while
  acquiring Giant when we wake up with slept locks.  This is ok because of
  Giant's special nature.
- Allow witness to differentiate between shared and exclusive locks and
  unlocks of a lock.  Witness will now detect the case when a lock is
  acquired first in one mode and then in another.  Mutexes are always
  locked and unlocked exclusively.  Witness will also now detect the case
  where a process attempts to unlock a shared lock while holding an
  exclusive lock and vice versa.
- Fix a bug in the lock list implementation where we used the wrong
  constant to detect the case where a lock list entry was full.
2001-05-04 17:15:16 +00:00
John Baldwin
192846463a Rework the witness code to work with sx locks as well as mutexes.
- Introduce lock classes and lock objects.  Each lock class specifies a
  name and set of flags (or properties) shared by all locks of a given
  type.  Currently there are three lock classes: spin mutexes, sleep
  mutexes, and sx locks.  A lock object specifies properties of an
  additional lock along with a lock name and all of the extra stuff needed
  to make witness work with a given lock.  This abstract lock stuff is
  defined in sys/lock.h.  The lockmgr constants, types, and prototypes have
  been moved to sys/lockmgr.h.  For temporary backwards compatability,
  sys/lock.h includes sys/lockmgr.h.
- Replace proc->p_spinlocks with a per-CPU list, PCPU(spinlocks), of spin
  locks held.  By making this per-cpu, we do not have to jump through
  magic hoops to deal with sched_lock changing ownership during context
  switches.
- Replace proc->p_heldmtx, formerly a list of held sleep mutexes, with
  proc->p_sleeplocks, which is a list of held sleep locks including sleep
  mutexes and sx locks.
- Add helper macros for logging lock events via the KTR_LOCK KTR logging
  level so that the log messages are consistent.
- Add some new flags that can be passed to mtx_init():
  - MTX_NOWITNESS - specifies that this lock should be ignored by witness.
    This is used for the mutex that blocks a sx lock for example.
  - MTX_QUIET - this is not new, but you can pass this to mtx_init() now
    and no events will be logged for this lock, so that one doesn't have
    to change all the individual mtx_lock/unlock() operations.
- All lock objects maintain an initialized flag.  Use this flag to export
  a mtx_initialized() macro that can be safely called from drivers.  Also,
  we on longer walk the all_mtx list if MUTEX_DEBUG is defined as witness
  performs the corresponding checks using the initialized flag.
- The lock order reversal messages have been improved to output slightly
  more accurate file and line numbers.
2001-03-28 09:03:24 +00:00
John Baldwin
7331c2a252 In order to avoid recursing on the backing mutex for sx locks in the
INVARIANTS case, define the actual KASSERT() in _SX_ASSERT_[SX]LOCKED
macros that are used in the sx code itself and convert the
SX_ASSERT_[SX]LOCKED macros to simple wrappers that grab the mutex for the
duration of the check.
2001-03-06 23:13:15 +00:00
Bosko Milekic
af76144992 - Add sx_descr description member to sx lock structure
- Add sx_xholder member to sx struct which is used for INVARIANTS-enabled
  assertions. It indicates the thread that presently owns the xlock.
- Add some assertions to the sx lock code that will detect the fatal
  API abuse:
     xlock --> xlock
     xlock --> slock
  which now works thanks to sx_xholder.
  Notice that the remaining two problematic cases:
     slock --> xlock
     slock --> slock (a little less problematic, but still recursion)
  will need to be handled by witness eventually, as they are more
  involved.

Reviewed by: jhb, jake, jasone
2001-03-06 06:17:05 +00:00
Jason Evans
6281b30a73 Implement shared/exclusive locks.
Reviewed by:	bmilekic, jake, jhb
2001-03-05 19:59:41 +00:00