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mtx: clean up locking spin mutexes

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1) shorten the fast path by pushing the lockstat probe to the slow path
2) test for kernel panic only after it turns out we will have to spin,
in particular test only after we know we are not recursing

MFC after:	1 week
This commit is contained in:
mjg 2017-10-20 00:30:35 +00:00
parent 906113c872
commit 96ff69bdc9
2 changed files with 39 additions and 16 deletions
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30
sys/kern/kern_mutex.c
View File

@ -289,6 +289,7 @@ __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
int line)
{
struct mtx *m;
uintptr_t tid, v;
if (SCHEDULER_STOPPED())
return;
@ -308,7 +309,14 @@ __mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
opts &= ~MTX_RECURSE;
WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
file, line, NULL);
__mtx_lock_spin(m, curthread, opts, file, line);
spinlock_enter();
tid = (uintptr_t)curthread;
v = MTX_UNOWNED;
if (!_mtx_obtain_lock_fetch(m, &v, tid))
_mtx_lock_spin(m, v, opts, file, line);
else
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire,
m, 0, 0, file, line);
LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
line);
WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
@ -682,12 +690,18 @@ _mtx_lock_spin_failed(struct mtx *m)
* This is only called if we need to actually spin for the lock. Recursion
* is handled inline.
*/
#if LOCK_DEBUG > 0
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, uintptr_t tid,
int opts, const char *file, int line)
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
const char *file, int line)
#else
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v)
#endif
{
struct mtx *m;
struct lock_delay_arg lda;
uintptr_t tid;
#ifdef LOCK_PROFILING
int contested = 0;
uint64_t waittime = 0;
@ -699,10 +713,7 @@ _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, uintptr_t tid,
int doing_lockprof;
#endif
if (SCHEDULER_STOPPED())
return;
lock_delay_arg_init(&lda, &mtx_spin_delay);
tid = (uintptr_t)curthread;
m = mtxlock2mtx(c);
if (__predict_false(v == MTX_UNOWNED))
@ -713,6 +724,11 @@ _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, uintptr_t tid,
return;
}
if (SCHEDULER_STOPPED())
return;
lock_delay_arg_init(&lda, &mtx_spin_delay);
if (LOCK_LOG_TEST(&m->lock_object, opts))
CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),

25
sys/sys/mutex.h
View File

@ -105,8 +105,12 @@ void __mtx_unlock_sleep(volatile uintptr_t *c);
#endif
#ifdef SMP
void _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, uintptr_t tid,
int opts, const char *file, int line);
#if LOCK_DEBUG > 0
void _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
const char *file, int line);
#else
void _mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v);
#endif
#endif
void __mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file,
int line);
@ -154,8 +158,13 @@ void thread_lock_flags_(struct thread *, int, const char *, int);
__mtx_unlock_sleep(&(m)->mtx_lock)
#endif
#ifdef SMP
#define _mtx_lock_spin(m, v, t, o, f, l) \
_mtx_lock_spin_cookie(&(m)->mtx_lock, v, t, o, f, l)
#if LOCK_DEBUG > 0
#define _mtx_lock_spin(m, v, o, f, l) \
_mtx_lock_spin_cookie(&(m)->mtx_lock, v, o, f, l)
#else
#define _mtx_lock_spin(m, v, o, f, l) \
_mtx_lock_spin_cookie(&(m)->mtx_lock, v)
#endif
#endif
#define _mtx_lock_flags(m, o, f, l) \
__mtx_lock_flags(&(m)->mtx_lock, o, f, l)
@ -219,11 +228,9 @@ void thread_lock_flags_(struct thread *, int, const char *, int);
uintptr_t _v = MTX_UNOWNED; \
\
spinlock_enter(); \
if (!_mtx_obtain_lock_fetch((mp), &_v, _tid)) \
_mtx_lock_spin((mp), _v, _tid, (opts), (file), (line)); \
else \
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, \
mp, 0, 0, file, line); \
if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire) || \
!_mtx_obtain_lock_fetch((mp), &_v, _tid))) \
_mtx_lock_spin((mp), _v, (opts), (file), (line)); \
} while (0)
#define __mtx_trylock_spin(mp, tid, opts, file, line) __extension__ ({ \
uintptr_t _tid = (uintptr_t)(tid); \