From c768e45ed336970a42e58e679804f0f455422cd8 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Wed, 8 Jun 2011 18:28:46 -0400 Subject: [PATCH] call_rcu: fix futex-based wakeup The initial decrement was missing from the implementation. It now behaves exactly like the urcu.c wait/wakeup code. Signed-off-by: Mathieu Desnoyers --- urcu-call-rcu-impl.h | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h index 69edd49..cfe1cce 100644 --- a/urcu-call-rcu-impl.h +++ b/urcu-call-rcu-impl.h @@ -212,6 +212,11 @@ static void *call_rcu_thread(void *arg) thread_call_rcu_data = crdp; for (;;) { + if (!(crdp->flags & URCU_CALL_RCU_RT)) { + uatomic_dec(&crdp->futex); + /* Decrement futex before reading call_rcu list */ + cmm_smp_mb(); + } if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) poll(NULL, 0, 1); @@ -235,15 +240,21 @@ static void *call_rcu_thread(void *arg) } while (cbs != NULL); uatomic_sub(&crdp->qlen, cbcount); } - if (crdp->flags & URCU_CALL_RCU_STOP) + if (crdp->flags & URCU_CALL_RCU_STOP) { + if (!(crdp->flags & URCU_CALL_RCU_RT)) { + /* + * Read call_rcu list before write futex. + */ + cmm_smp_mb(); + uatomic_set(&crdp->futex, 0); + } break; - if (crdp->flags & URCU_CALL_RCU_RT) - poll(NULL, 0, 10); - else { + } + if (!(crdp->flags & URCU_CALL_RCU_RT)) { if (&crdp->cbs.head == _CMM_LOAD_SHARED(crdp->cbs.tail)) call_rcu_wait(crdp); - poll(NULL, 0, 10); } + poll(NULL, 0, 10); } call_rcu_lock(&crdp->mtx); crdp->flags |= URCU_CALL_RCU_STOPPED; -- 2.34.1