Module Name: src
Committed By: yamt
Date: Mon Apr 6 09:34:15 UTC 2015
Modified Files:
src/libexec/ld.elf_so: rtld.c
Log Message:
Fix membars around rtld internal mutex.
This fixes the most of lockups i observed with Open vSwitch
on NetBSD/amd64. ("most of" because it still occasionally
locks up because of other problems. see PR/49816)
To generate a diff of this commit:
cvs rdiff -u -r1.176 -r1.177 src/libexec/ld.elf_so/rtld.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/libexec/ld.elf_so/rtld.c
diff -u src/libexec/ld.elf_so/rtld.c:1.176 src/libexec/ld.elf_so/rtld.c:1.177
--- src/libexec/ld.elf_so/rtld.c:1.176 Sat Apr 4 18:51:57 2015
+++ src/libexec/ld.elf_so/rtld.c Mon Apr 6 09:34:15 2015
@@ -1,4 +1,4 @@
-/* $NetBSD: rtld.c,v 1.176 2015/04/04 18:51:57 joerg Exp $ */
+/* $NetBSD: rtld.c,v 1.177 2015/04/06 09:34:15 yamt Exp $ */
/*
* Copyright 1996 John D. Polstra.
@@ -40,7 +40,7 @@
#include <sys/cdefs.h>
#ifndef lint
-__RCSID("$NetBSD: rtld.c,v 1.176 2015/04/04 18:51:57 joerg Exp $");
+__RCSID("$NetBSD: rtld.c,v 1.177 2015/04/06 09:34:15 yamt Exp $");
#endif /* not lint */
#include <sys/param.h>
@@ -1544,6 +1544,7 @@ _rtld_shared_enter(void)
/* Yes, so increment use counter */
if (atomic_cas_uint(&_rtld_mutex, cur, cur + 1) != cur)
continue;
+ membar_enter();
return;
}
/*
@@ -1561,6 +1562,7 @@ _rtld_shared_enter(void)
/*
* Check for race against _rtld_exclusive_exit before sleeping.
*/
+ membar_sync();
if ((_rtld_mutex & RTLD_EXCLUSIVE_MASK) ||
_rtld_waiter_exclusive)
_lwp_park(CLOCK_REALTIME, 0, NULL, 0,
@@ -1588,12 +1590,12 @@ _rtld_shared_exit(void)
* Wakeup LWPs waiting for an exclusive lock if this is the last
* LWP on the shared lock.
*/
+ membar_exit();
if (atomic_dec_uint_nv(&_rtld_mutex))
return;
+ membar_sync();
if ((waiter = _rtld_waiter_exclusive) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
-
- membar_exit();
}
void
@@ -1608,12 +1610,13 @@ _rtld_exclusive_enter(sigset_t *mask)
sigdelset(&blockmask, SIGTRAP); /* Allow the debugger */
sigprocmask(SIG_BLOCK, &blockmask, mask);
- membar_enter();
-
for (;;) {
- if (atomic_cas_uint(&_rtld_mutex, 0, locked_value) == 0)
+ if (atomic_cas_uint(&_rtld_mutex, 0, locked_value) == 0) {
+ membar_enter();
break;
+ }
waiter = atomic_swap_uint(&_rtld_waiter_exclusive, self);
+ membar_sync();
cur = _rtld_mutex;
if (cur == locked_value) {
_rtld_error("dead lock detected");
@@ -1633,13 +1636,14 @@ _rtld_exclusive_exit(sigset_t *mask)
{
lwpid_t waiter;
+ membar_exit();
_rtld_mutex = 0;
+ membar_sync();
if ((waiter = _rtld_waiter_exclusive) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
if ((waiter = _rtld_waiter_shared) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
- membar_exit();
sigprocmask(SIG_SETMASK, mask, NULL);
}
