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mtx: eliminate recursion support from thread lock

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Now that it is not used after schedlock changes got merged.

Note the unlock routine temporarily still checks for it on account of just using
regular spin unlock.

This is a prelude towards a general clean up.
This commit is contained in:
Mateusz Guzik 2019-12-16 00:04:33 +00:00
parent 5233eb9dc6
commit 3fd19ce7a5
1 changed files with 10 additions and 22 deletions
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32
sys/kern/kern_mutex.c
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@ -797,10 +797,9 @@ thread_lock_validate(struct mtx *m, int opts, const char *file, int line)
KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
("thread_lock() of sleep mutex %s @ %s:%d",
m->lock_object.lo_name, file, line));
if (mtx_owned(m))
KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0,
("thread_lock: recursed on non-recursive mutex %s @ %s:%d\n",
m->lock_object.lo_name, file, line));
KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) == 0,
("thread_lock: got a recursive mutex %s @ %s:%d\n",
m->lock_object.lo_name, file, line));
WITNESS_CHECKORDER(&m->lock_object,
opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
}
@ -818,7 +817,7 @@ _thread_lock(struct thread *td)
#endif
{
struct mtx *m;
uintptr_t tid, v;
uintptr_t tid;
tid = (uintptr_t)curthread;
@ -827,19 +826,14 @@ _thread_lock(struct thread *td)
spinlock_enter();
m = td->td_lock;
thread_lock_validate(m, 0, file, line);
v = MTX_READ_VALUE(m);
if (__predict_true(v == MTX_UNOWNED)) {
if (__predict_false(!_mtx_obtain_lock(m, tid)))
goto slowpath_unlocked;
} else if (v == tid) {
m->mtx_recurse++;
} else
if (__predict_false(m == &blocked_lock))
goto slowpath_unlocked;
if (__predict_false(!_mtx_obtain_lock(m, tid)))
goto slowpath_unlocked;
if (__predict_true(m == td->td_lock)) {
WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line);
return;
}
MPASS(m->mtx_recurse == 0);
_mtx_release_lock_quick(m);
slowpath_unlocked:
spinlock_exit();
@ -907,11 +901,7 @@ retry:
break;
continue;
}
if (v == tid) {
m->mtx_recurse++;
MPASS(m == td->td_lock);
break;
}
MPASS(v != tid);
lock_profile_obtain_lock_failed(&m->lock_object,
&contested, &waittime);
/* Give interrupts a chance while we spin. */
@ -932,7 +922,6 @@ retry:
}
if (m == td->td_lock)
break;
MPASS(m->mtx_recurse == 0);
_mtx_release_lock_quick(m);
}
LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
@ -946,9 +935,8 @@ retry:
#ifdef KDTRACE_HOOKS
spin_time += lockstat_nsecs(&m->lock_object);
#endif
if (m->mtx_recurse == 0)
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m,
contested, waittime, file, line);
LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(spin__acquire, m, contested,
waittime, file, line);
#ifdef KDTRACE_HOOKS
if (lda.spin_cnt != 0)
LOCKSTAT_RECORD1(thread__spin, m, spin_time);