Rich Felker
4e98cce1c5
as a result of commit 12e1e32468, kernel
processing of the robust list is only needed for process-shared
mutexes. previously the first attempt to lock any owner-tracked mutex
resulted in robust list initialization and a set_robust_list syscall.
this is no longer necessary, and since the kernel's record of the
robust list must now be cleared at thread exit time for detached
threads, optimizing it out is more worthwhile than before too.
59 lines
1.5 KiB
C
59 lines
1.5 KiB
C
#include "pthread_impl.h"
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int __pthread_mutex_trylock_owner(pthread_mutex_t *m)
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{
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int old, own;
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int type = m->_m_type & 15;
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pthread_t self = __pthread_self();
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int tid = self->tid;
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old = m->_m_lock;
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own = old & 0x7fffffff;
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if (own == tid && (type&3) == PTHREAD_MUTEX_RECURSIVE) {
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if ((unsigned)m->_m_count >= INT_MAX) return EAGAIN;
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m->_m_count++;
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return 0;
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}
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if (own == 0x40000000) return ENOTRECOVERABLE;
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if (m->_m_type & 128) {
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if (!self->robust_list.off) {
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self->robust_list.off = (char*)&m->_m_lock-(char *)&m->_m_next;
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__syscall(SYS_set_robust_list, &self->robust_list, 3*sizeof(long));
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}
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if (m->_m_waiters) tid |= 0x80000000;
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self->robust_list.pending = &m->_m_next;
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}
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if ((own && (!(own & 0x40000000) || !(type & 4)))
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|| a_cas(&m->_m_lock, old, tid) != old) {
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self->robust_list.pending = 0;
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return EBUSY;
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}
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volatile void *next = self->robust_list.head;
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m->_m_next = next;
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m->_m_prev = &self->robust_list.head;
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if (next != &self->robust_list.head) *(volatile void *volatile *)
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((char *)next - sizeof(void *)) = &m->_m_next;
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self->robust_list.head = &m->_m_next;
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self->robust_list.pending = 0;
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if (own) {
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m->_m_count = 0;
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m->_m_type |= 8;
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return EOWNERDEAD;
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}
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return 0;
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}
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int __pthread_mutex_trylock(pthread_mutex_t *m)
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{
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if ((m->_m_type&15) == PTHREAD_MUTEX_NORMAL)
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return a_cas(&m->_m_lock, 0, EBUSY) & EBUSY;
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return __pthread_mutex_trylock_owner(m);
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}
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weak_alias(__pthread_mutex_trylock, pthread_mutex_trylock);
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