From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josht@linux.vnet.ibm.com, dvhltc@us.ibm.com, niv@us.ibm.com,
tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/3] Need to update rnp->gpnum if preemptable RCU is to be reliable.
Date: Tue, 8 Sep 2009 15:54:36 -0700 [thread overview]
Message-ID: <12524504771622-git-send-email-> (raw)
In-Reply-To: <20090908225349.GA19524@linux.vnet.ibm.com>
From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Without this patch, tasks preempted in RCU read-side critical sections
can fail to block the grace period, given that rnp->gpnum is used to
determine which rnp->blocked_tasks[] element the preempted task is
enqueued on. Before the patch, rnp->gpnum is always zero, so preempted
tasks are always enqueued on rnp->blocked_tasks[0], which is correct
only when the current CPU has not checked into the current grace period
and the grace-period number is even, or, similarly, if the current CPU
-has- checked into the current grace period and the grace-period number
is odd.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 71bc797..03866bd 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -627,6 +627,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
/* Special-case the common single-level case. */
if (NUM_RCU_NODES == 1) {
rnp->qsmask = rnp->qsmaskinit;
+ rnp->gpnum = rsp->gpnum;
rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
spin_unlock_irqrestore(&rnp->lock, flags);
return;
@@ -652,8 +653,10 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
*/
rnp_end = rsp->level[NUM_RCU_LVLS - 1];
- for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++)
+ for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++) {
rnp_cur->qsmask = rnp_cur->qsmaskinit;
+ rnp->gpnum = rsp->gpnum;
+ }
/*
* Now set up the leaf nodes. Here we must be careful. First,
@@ -674,6 +677,7 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
for (; rnp_cur < rnp_end; rnp_cur++) {
spin_lock(&rnp_cur->lock); /* irqs already disabled. */
rnp_cur->qsmask = rnp_cur->qsmaskinit;
+ rnp->gpnum = rsp->gpnum;
spin_unlock(&rnp_cur->lock); /* irqs already disabled. */
}
--
1.5.2.5
next prev parent reply other threads:[~2009-09-08 22:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-08 22:53 [PATCH tip/core/rcu 0/3] increase rcutorture intensity and fix a couple resulting bugs Paul E. McKenney
2009-09-08 22:54 ` [PATCH tip/core/rcu 1/3] rcutorture: Occasionally delay readers enough to make RCU force_quiescent_state Paul E. McKenney
2009-09-12 7:45 ` Ingo Molnar
2009-09-12 14:36 ` Paul E. McKenney
2009-09-12 7:55 ` [tip:core/urgent] " tip-bot for Josh Triplett
2009-09-17 22:10 ` tip-bot for Josh Triplett
2009-09-08 22:54 ` Paul E. McKenney [this message]
2009-09-12 7:55 ` [tip:core/urgent] rcu: Need to update rnp->gpnum if preemptable RCU is to be reliable tip-bot for Paul E. McKenney
2009-09-17 22:10 ` tip-bot for Paul E. McKenney
2009-09-08 22:54 ` [PATCH tip/core/rcu 3/3] Initialize multi-level RCU grace periods holding locks Paul E. McKenney
2009-09-12 7:55 ` [tip:core/urgent] rcu: " tip-bot for Paul E. McKenney
2009-09-17 22:10 ` tip-bot for Paul E. McKenney
2009-09-08 23:37 ` [PATCH tip/core/rcu 0/3] increase rcutorture intensity and fix a couple resulting bugs Steven Rostedt
2009-09-09 17:43 ` Valdis.Kletnieks
2009-09-09 18:23 ` Paul E. McKenney
2009-09-12 7:46 ` Ingo Molnar
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