6.4-stable review patch. If anyone has any objections, please let me know.
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From: Paul Gortmaker paul.gortmaker@windriver.com
[ Upstream commit 96c1fa04f089a7e977a44e4e8fdc92e81be20bef ]
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.... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 4df14db4da490..87015e9deacc9 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",