From f83c5ad964c09857faa22dd99fb2537f290a979f Mon Sep 17 00:00:00 2001 From: Pranith Kumar K Date: Tue, 23 Jun 2015 06:39:49 +0530 Subject: [PATCH 128/129] cluster/ec: Avoid parallel executions of the same state machine Backport of http://review.gluster.org/11317 In very rare circumstances it was possible that a subfop started by another fop could finish fast enough to cause that two or more instances of the same state machine be executing at the same time. Change-Id: I319924a18bd3f88115e751a66f8f4560435e0e0e BUG: 1230513 Signed-off-by: Xavier Hernandez Reviewed-on: https://code.engineering.redhat.com/gerrit/51301 Reviewed-by: Pranith Kumar Karampuri Tested-by: Pranith Kumar Karampuri --- xlators/cluster/ec/src/ec-common.c | 25 ++++++++++++------------- 1 files changed, 12 insertions(+), 13 deletions(-) diff --git a/xlators/cluster/ec/src/ec-common.c b/xlators/cluster/ec/src/ec-common.c index be69c57..f69234e 100644 --- a/xlators/cluster/ec/src/ec-common.c +++ b/xlators/cluster/ec/src/ec-common.c @@ -250,7 +250,7 @@ int32_t ec_check_complete(ec_fop_data_t * fop, ec_resume_f resume) GF_ASSERT(fop->resume == NULL); - if (fop->jobs != 0) + if (--fop->jobs != 0) { ec_trace("WAIT", fop, "resume=%p", resume); @@ -1259,11 +1259,6 @@ void ec_lock(ec_fop_data_t *fop) ec_lock_link_t *timer_link = NULL; ec_lock_t *lock; - /* There is a chance that ec_resume is called on fop even before ec_sleep. - * Which can result in refs == 0 for fop leading to use after free in this - * function when it calls ec_sleep so do ec_sleep at start and end of this - * function.*/ - ec_sleep (fop); while (fop->locked < fop->lock_count) { /* Since there are only up to 2 locks per fop, this xor will change * the order of the locks if fop->first_lock is 1. */ @@ -1328,7 +1323,6 @@ void ec_lock(ec_fop_data_t *fop) timer_link = NULL; } } - ec_resume (fop, 0); if (timer_link != NULL) { ec_resume(timer_link->fop, 0); @@ -1725,15 +1719,9 @@ void ec_unlock(ec_fop_data_t *fop) { int32_t i; - /*If fop->lock_count > 1 then there is a chance that by the time - * ec_unlock_timer_add() is called for the second lock epoll thread could - * reply inodelk and jobs will be '0' leading to completion of state - * machine and freeing of fop. So add sleep/resume*/ - ec_sleep (fop); for (i = 0; i < fop->lock_count; i++) { ec_unlock_timer_add(&fop->locks[i]); } - ec_resume (fop, 0); } void @@ -1879,6 +1867,17 @@ void __ec_manager(ec_fop_data_t * fop, int32_t error) break; } + /* At each state, fop must not be used anywhere else and there + * shouldn't be any pending subfop going on. */ + GF_ASSERT(fop->jobs == 0); + + /* While the manager is running we need to avoid that subfops launched + * from it could finish and call ec_resume() before the fop->handler + * has completed. This could lead to the same manager being executed + * by two threads concurrently. ec_check_complete() will take care of + * this reference. */ + fop->jobs = 1; + fop->state = fop->handler(fop, fop->state); error = ec_check_complete(fop, __ec_manager); -- 1.7.1