From 0b362d6f999cbbe4b1a0d8cee2a9fb9a34422b7a Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 3 Mar 2011 11:46:20 -0500 Subject: [PATCH] fork: child should issue synchronize_rcu() for urcu-bp garbage collection After a fork(), the child process should execute synchronize_rcu() before any new thread can be created. Failure to do so could lead to a deadlock in the unlikely scenario where a thread ID appearing in the parent is reused in the child before GC is performed. Signed-off-by: Mathieu Desnoyers --- libust/tracectl.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/libust/tracectl.c b/libust/tracectl.c index bef4537..3b60975 100644 --- a/libust/tracectl.c +++ b/libust/tracectl.c @@ -1711,7 +1711,7 @@ static void ust_after_fork_common(ust_fork_info_t *fork_info) void ust_after_fork_parent(ust_fork_info_t *fork_info) { - /* Reenable signals */ + /* Release mutexes and reenable signals */ ust_after_fork_common(fork_info); } @@ -1720,7 +1720,15 @@ void ust_after_fork_child(ust_fork_info_t *fork_info) /* First sanitize the child */ ust_fork(); - /* Then reenable interrupts */ + /* Then release mutexes and reenable signals */ ust_after_fork_common(fork_info); + + /* + * Make sure we clean up the urcu-bp thread list in the child by running + * the garbage collection before any pthread_create can be called. + * Failure to do so could lead to a deadlock caused by reuse of a thread + * ID before urcu-bp garbage collection is performed. + */ + synchronize_rcu(); } -- 2.34.1