Currently there's an issue which is not always reproducible, where the
softirqs annotation in lockdep goes out of sync with the reality of the
world and causes a lockdep splat. This is because the preemptoff tracer
calls into lockdep which can cause a softirqs invalid annotation splat.
The same issue was fixed in local_bh_disable_ip.
/*
* The preempt tracer hooks into preempt_count_add and will break
* lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
* is set and before current->softirq_enabled is cleared.
* We must manually increment preempt_count here and manually
* call the trace_preempt_off later.
*/
I am not fully sure why the issue is reproducible with my patches easily,
but it seems like the same ordering issue can exist so we ought to fix
it.
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Peter Zilstra <pet...@infradead.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Cc: Tom Zanussi <tom.zanu...@linux.intel.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Thomas Glexiner <t...@linutronix.de>
Cc: Boqun Feng <boqun.f...@gmail.com>
Cc: Paul McKenney <paul...@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweis...@gmail.com>
Cc: Randy Dunlap <rdun...@infradead.org>
Cc: Masami Hiramatsu <mhira...@kernel.org>
Cc: Fenguang Wu <fengguang...@intel.com>
Cc: Baohong Liu <baohong....@intel.com>
Cc: Vedang Patel <vedang.pa...@intel.com>
Signed-off-by: Joel Fernandes <joe...@google.com>
---
kernel/softirq.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 177de3640c78..8a040bcaa033 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -139,9 +139,13 @@ static void __local_bh_enable(unsigned int cnt)
{
lockdep_assert_irqs_disabled();
+ if (preempt_count() == cnt)
+ trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+
if (softirq_count() == (cnt & SOFTIRQ_MASK))
trace_softirqs_on(_RET_IP_);
- preempt_count_sub(cnt);
+
+ __preempt_count_sub(cnt);
}
/*
--
2.17.0.484.g0c8726318c-goog
