Attachment 897574 Details for Bug 1099509 – Fix for bdb issue #3514381

[patch] Fix for bdb issue #3514381

0001-Fix-a-CDB-race.patch (text/plain), 3.97 KB, created by Lubomir Rintel on 2014-05-20 13:34:12 UTC

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Creator: Lubomir Rintel

Created: 2014-05-20 13:34:12 UTC

Size: 3.97 KB

patch

obsolete

>From 4ae2eb88fadc256ddf9862b2e72ed216ddbb919d Mon Sep 17 00:00:00 2001
>From: michael brey <michael.brey@oracle.com>
>Date: Tue, 20 May 2014 14:49:44 +0200
>Subject: [PATCH] Fix a CDB race
>
>Report and reproducer here:
>https://community.oracle.com/thread/3514381
>
>From: michael brey <michael.brey@oracle.com>
>To: Lubomir Rintel <lkundrak@v3.sk>
>Subject: Re: BDB crash
>Date: Tue, 13 May 2014 09:07:45 -0600 (05/13/2014 05:07:45 PM)
>Message-id: <53723541.7040203@oracle.com>
>
>  attached are patches for each release.  the 5.3.28 patch will apply on
>top of 5.3.21.
>
>thanks
>mike
>---
> src/env/env_failchk.c | 24 ++++++++++++++++++++++++
> src/mutex/mut_tas.c   | 18 +++++++++++++++++-
> 2 files changed, 41 insertions(+), 1 deletion(-)
>
>diff --git a/src/env/env_failchk.c b/src/env/env_failchk.c
>index 05752f0..b09df96 100644
>--- a/src/env/env_failchk.c
>+++ b/src/env/env_failchk.c
>@@ -312,6 +312,7 @@ __env_in_api(env)
> 	REGINFO *infop;
> 	THREAD_INFO *thread;
> 	u_int32_t i;
>+	pid_t pid;
> 	int unpin, ret;
> 
> 	if ((htab = env->thr_hashtab) == NULL)
>@@ -325,6 +326,7 @@ __env_in_api(env)
> 
> 	for (i = 0; i < env->thr_nbucket; i++)
> 		SH_TAILQ_FOREACH(ip, &htab[i], dbth_links, __db_thread_info) {
>+			pid = ip->dbth_pid;
> 			if (ip->dbth_state == THREAD_SLOT_NOT_IN_USE ||
> 			    (ip->dbth_state == THREAD_OUT &&
> 			    thread->thr_count <  thread->thr_max))
>@@ -341,6 +343,28 @@ __env_in_api(env)
> 				ip->dbth_state = THREAD_SLOT_NOT_IN_USE;
> 				continue;
> 			}
>+			/*
>+			 * The above tests are not atomic, so it is possible that
>+			 * the process pointed by ip has changed during the tests.
>+			 * In particular, if the process pointed by ip when is_alive
>+			 * was executed terminated normally, a new process may reuse
>+			 * the same ip structure and change its dbth_state before the
>+			 * next two tests were performed. Therefore, we need to test
>+			 * here that all four tests above are done on the same process.
>+			 * If the process pointed by ip changed, all tests are invalid
>+			 * and can be ignored.
>+			 * Similarly, it's also possible for two processes racing to
>+			 * change the dbth_state of the same ip structure. For example,
>+			 * both process A and B reach the above test for the same
>+			 * terminated process C where C's dbth_state is THREAD_OUT.
>+			 * If A goes into the 'if' block and changes C's dbth_state to
>+			 * THREAD_SLOT_NOT_IN_USE before B checks the condition, B
>+			 * would incorrectly fail the test and run into this line.
>+			 * Therefore, we need to check C's dbth_state again and fail
>+			 * the db only if C's dbth_state is indeed THREAD_ACTIVE.
>+			 */
>+			if (ip->dbth_state != THREAD_ACTIVE || ip->dbth_pid != pid)
>+				continue;
> 			return (__db_failed(env, DB_STR("1507",
> 			    "Thread died in Berkeley DB library"),
> 			    ip->dbth_pid, ip->dbth_tid));
>diff --git a/src/mutex/mut_tas.c b/src/mutex/mut_tas.c
>index 0899d23..db95030 100644
>--- a/src/mutex/mut_tas.c
>+++ b/src/mutex/mut_tas.c
>@@ -151,10 +151,26 @@ loop:	/* Attempt to acquire the resource for N spins. */
> 			if (F_ISSET(dbenv, DB_ENV_FAILCHK) &&
> 			    ip == NULL && dbenv->is_alive(dbenv,
> 			    mutexp->pid, mutexp->tid, 0) == 0) {
>+				/*
>+				 * The process owing the mutex is "dead" now, but it may
>+				 * have already released the mutex. We need to check again
>+				 * by going back to the top of the loop
>+				 * if the mutex is still held by the "dead" process. We
>+				 * yield 10 us to increase the likelyhood of mutexp fields
>+				 * being up-to-date. Set spin so we spin one more time
>+				 * because no need to spin more if dead process owns mutex.
>+				 */                               
>+				if (nspins > 1) {
>+					nspins = 2;
>+					__os_yield(env, 0, 10);
>+					continue;
>+				}
> 				ret = __env_set_state(env, &ip, THREAD_VERIFY);
> 				if (ret != 0 ||
>-				    ip->dbth_state == THREAD_FAILCHK)
>+				    ip->dbth_state == THREAD_FAILCHK) {
>+					printf("mut_tas:172, pid: %d, flag: %d\n", mutexp->pid, mutexp->flags);
> 					return (DB_RUNRECOVERY);
>+				}
> 			}
> 			if (nowait)
> 				return (DB_LOCK_NOTGRANTED);
>-- 
>1.8.3.1
>

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