From: "Paul E. McKenney" paulmck@kernel.org
mainline inclusion from mainline-v5.13-rc1 commit 1c0c4bc1ceb580851b2d76fdef9712b3bdae134b category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6O293 CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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If there is heavy softirq activity, the softirq system will attempt to awaken ksoftirqd and will stop the traditional back-of-interrupt softirq processing. This is all well and good, but only if the ksoftirqd kthreads already exist, which is not the case during early boot, in which case the system hangs.
One reproducer is as follows:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 2 --configs "TREE03" --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_NO_HZ_IDLE=y CONFIG_HZ_PERIODIC=n" --bootargs "threadirqs=1" --trust-make
This commit therefore adds a couple of existence checks for ksoftirqd and forces back-of-interrupt softirq processing when ksoftirqd does not yet exist. With this change, the above test passes.
Reported-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Reported-by: Uladzislau Rezki urezki@gmail.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de [ paulmck: Remove unneeded check per Sebastian Siewior feedback. ] Reviewed-by: Frederic Weisbecker frederic@kernel.org Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Lin Yujun linyujun809@huawei.com Reviewed-by: Zhang Jianhua chris.zjh@huawei.com Reviewed-by: Liao Chang liaochang1@huawei.com Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- kernel/softirq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c index 09229ad82209..19668d614f47 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -376,7 +376,7 @@ static inline void invoke_softirq(void) if (ksoftirqd_running(local_softirq_pending())) return;
- if (!force_irqthreads) { + if (!force_irqthreads || !__this_cpu_read(ksoftirqd)) { #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK /* * We can safely execute softirq on the current stack if