From 6a23a4e0f94cf10ac6faa709e3827b13563e4ee3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 18 Jun 2014 09:18:31 -0700 Subject: [PATCH] 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 --- 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 2c4da8150994..6b65937664ac 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))) -- 2.39.5