Commit-ID: bc1dce514e9b29b64df28a533015885862f47814
Gitweb: http://git.kernel.org/tip/bc1dce514e9b29b64df28a533015885862f47814
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Wed, 18 Jun 2014 09:18:31 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Wed, 9 Jul 2014 09:15:04 -0700
rcu: Don't use NMIs to dump other CPUs' stacks
Although NMI-based stack dumps are in principle more accurate, they are
also more likely to trigger deadlocks. This commit therefore replaces
all uses of trigger_all_cpu_backtrace() with rcu_dump_cpu_stacks(), so
that the CPU detecting an RCU CPU stall does the stack dumping.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 3f93033..8f3e4d4 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1013,10 +1013,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp)
}
/*
- * Dump stacks of all tasks running on stalled CPUs. This is a fallback
- * for architectures that do not implement trigger_all_cpu_backtrace().
- * The NMI-triggered stack traces are more accurate because they are
- * printed by the target CPU.
+ * Dump stacks of all tasks running on stalled CPUs.
*/
static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
{
@@ -1094,7 +1091,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
(long)rsp->gpnum, (long)rsp->completed, totqlen);
if (ndetected == 0)
pr_err("INFO: Stall ended before state dump start\n");
- else if (!trigger_all_cpu_backtrace())
+ else
rcu_dump_cpu_stacks(rsp);
/* Complain about tasks blocking the grace period. */
@@ -1125,8 +1122,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n",
jiffies - rsp->gp_start,
(long)rsp->gpnum, (long)rsp->completed, totqlen);
- if (!trigger_all_cpu_backtrace())
- dump_stack();
+ rcu_dump_cpu_stacks(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall)))
--
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