Commit f8e48a3d authored Oct 22, 2020 by Peter Zijlstra

lockdep: Fix preemption WARN for spurious IRQ-enable



It is valid (albeit uncommon) to call local_irq_enable() without first
having called local_irq_disable(). In this case we enter
lockdep_hardirqs_on*() with IRQs enabled and trip a preemption warning
for using __this_cpu_read().

Use this_cpu_read() instead to avoid the warning.

Fixes: 4d004099 ("lockdep: Fix lockdep recursion")
Reported-by:  <syzbot+53f8ce8bbc07924b6417@syzkaller.appspotmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

parent ed3e4537

kernel/locking/lockdep.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -4057,7 +4057,7 @@ void lockdep_hardirqs_on_prepare(unsigned long ip)
		if (unlikely(in_nmi()))
		return;

		if (unlikely(__this_cpu_read(lockdep_recursion)))
		if (unlikely(this_cpu_read(lockdep_recursion)))
		return;

		if (unlikely(lockdep_hardirqs_enabled())) {
		@@ -4126,7 +4126,7 @@ void noinstr lockdep_hardirqs_on(unsigned long ip)
		goto skip_checks;
		}

		if (unlikely(__this_cpu_read(lockdep_recursion)))
		if (unlikely(this_cpu_read(lockdep_recursion)))
		return;

		if (lockdep_hardirqs_enabled()) {