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authorPaul Gortmaker <paul.gortmaker@windriver.com>2023-08-18 16:07:57 -0400
committerThomas Gleixner <tglx@linutronix.de>2023-08-30 12:20:28 +0200
commit96c1fa04f089a7e977a44e4e8fdc92e81be20bef (patch)
tree12acfb4dcea391c717c686110d77dac07e8b9840 /kernel
parent2dde18cd1d8fac735875f2e4987f11817cc0bc2c (diff)
tick/rcu: Fix false positive "softirq work is pending" messages
In commit 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") the new function report_idle_softirq() was created by breaking code out of the existing can_stop_idle_tick() for kernels v5.18 and newer. In doing so, the code essentially went from a one conditional: if (a && b && c) warn(); to a three conditional: if (!a) return; if (!b) return; if (!c) return; warn(); But that conversion got the condition for the RT specific local_bh_blocked() wrong. The original condition was: !local_bh_blocked() but the conversion failed to negate it so it ended up as: if (!local_bh_blocked()) return false; This issue lay dormant until another fixup for the same commit was added in commit a7e282c77785 ("tick/rcu: Fix bogus ratelimit condition"). This commit realized the ratelimit was essentially set to zero instead of ten, and hence *no* softirq pending messages would ever be issued. Once this commit was backported via linux-stable, both the v6.1 and v6.4 preempt-rt kernels started printing out 10 instances of this at boot: NOHZ tick-stop error: local softirq work is pending, handler #80!!! Remove the negation and return when local_bh_blocked() evaluates to true to bring the correct behaviour back. Fixes: 0345691b24c0 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de> Reviewed-by: Wen Yang <wenyang.linux@foxmail.com> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230818200757.1808398-1-paul.gortmaker@windriver.com
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/tick-sched.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4df14db4da49..87015e9deacc 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -1045,7 +1045,7 @@ static bool report_idle_softirq(void)
return false;
/* On RT, softirqs handling may be waiting on some lock */
- if (!local_bh_blocked())
+ if (local_bh_blocked())
return false;
pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n",