diff options
| author | Paul Gortmaker <paul.gortmaker@windriver.com> | 2023-08-18 23:07:57 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-09-13 10:42:57 +0300 |
| commit | 55a448e8d86342a09e207c58675b65213509db2f (patch) | |
| tree | 668a77add2a639d75b4bfcc3bf4f48310df2c306 | |
| parent | 69b8d7bf834c3fcc598aadcf78a736a871befc17 (diff) | |
| download | linux-55a448e8d86342a09e207c58675b65213509db2f.tar.xz | |
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@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
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/time/tick-sched.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 1ad89eec2a55..798e1841d286 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -1050,7 +1050,7 @@ 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", |