Author: kib
Date: Tue Jan 24 17:30:13 2017
New Revision: 312701
URL: https://svnweb.freebsd.org/changeset/base/312701
Log:
MFC r311886:
Fix acquisition of nested write compat rtld locks.
PR: 215826
Modified:
stable/10/libexec/rtld-elf/rtld_lock.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/libexec/rtld-elf/rtld_lock.c
==============================================================================
--- stable/10/libexec/rtld-elf/rtld_lock.c Tue Jan 24 16:47:06 2017
(r312700)
+++ stable/10/libexec/rtld-elf/rtld_lock.c Tue Jan 24 17:30:13 2017
(r312701)
@@ -64,7 +64,7 @@ typedef struct Struct_Lock {
} Lock;
static sigset_t fullsigmask, oldsigmask;
-static int thread_flag;
+static int thread_flag, wnested;
static void *
def_lock_create(void)
@@ -117,29 +117,34 @@ def_rlock_acquire(void *lock)
static void
def_wlock_acquire(void *lock)
{
- Lock *l = (Lock *)lock;
- sigset_t tmp_oldsigmask;
+ Lock *l;
+ sigset_t tmp_oldsigmask;
- for ( ; ; ) {
- sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask);
- if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
- break;
- sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL);
- }
- oldsigmask = tmp_oldsigmask;
+ l = (Lock *)lock;
+ for (;;) {
+ sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask);
+ if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
+ break;
+ sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL);
+ }
+ if (atomic_fetchadd_int(&wnested, 1) == 0)
+ oldsigmask = tmp_oldsigmask;
}
static void
def_lock_release(void *lock)
{
- Lock *l = (Lock *)lock;
+ Lock *l;
- if ((l->lock & WAFLAG) == 0)
- atomic_add_rel_int(&l->lock, -RC_INCR);
- else {
- atomic_add_rel_int(&l->lock, -WAFLAG);
- sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
- }
+ l = (Lock *)lock;
+ if ((l->lock & WAFLAG) == 0)
+ atomic_add_rel_int(&l->lock, -RC_INCR);
+ else {
+ assert(wnested > 0);
+ atomic_add_rel_int(&l->lock, -WAFLAG);
+ if (atomic_fetchadd_int(&wnested, -1) == 1)
+ sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
+ }
}
static int
@@ -373,12 +378,12 @@ _rtld_atfork_pre(int *locks)
return;
/*
- * Warning: this does not work with the rtld compat locks
- * above, since the thread signal mask is corrupted (set to
- * all signals blocked) if two locks are taken in write mode.
- * The caller of the _rtld_atfork_pre() must provide the
- * working implementation of the locks, and libthr locks are
- * fine.
+ * Warning: this did not worked well with the rtld compat
+ * locks above, when the thread signal mask was corrupted (set
+ * to all signals blocked) if two locks were taken
+ * simultaneously in the write mode. The caller of the
+ * _rtld_atfork_pre() must provide the working implementation
+ * of the locks anyway, and libthr locks are fine.
*/
wlock_acquire(rtld_phdr_lock, &ls[0]);
wlock_acquire(rtld_bind_lock, &ls[1]);
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