This is a note to let you know that I've just added the patch titled
tick/rcu: Fix false positive "softirq work is pending" messages
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tick-rcu-fix-false-positive-softirq-work-is-pending-.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 55384ea86b38739f24befa15ca48fb465f7d2bb0
Author: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Date: Fri Aug 18 16:07:57 2023 -0400
tick/rcu: Fix false positive "softirq work is pending" messages
[ 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@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
Reviewed-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230818200757.1808398-1-paul.gortmaker@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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",
