softirq/preempt: Add missing current->preempt_disable_ip update

While debugging some "sleeping function called from invalid context" bug I
realized that the debugging message "Preemption disabled at:" pointed to
an incorrect function.

In particular if the last function/action that disabled preemption was
spin_lock_bh() then current->preempt_disable_ip won't be updated.

The reason for this is that __local_bh_disable_ip() will increase
preempt_count manually instead of calling preempt_count_add(), which
would handle the update correctly.

It look like the manual handling was done to work around some lockdep issue.

So add the missing update of current->preempt_disable_ip to
__local_bh_disable_ip() as well.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150107090441.GC4365@osiris
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 501baa9..b9ae816 100644 (file)
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -114,8 +114,12 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
                trace_softirqs_off(ip);
        raw_local_irq_restore(flags);
 
-       if (preempt_count() == cnt)
+       if (preempt_count() == cnt) {
+#ifdef CONFIG_DEBUG_PREEMPT
+               current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1);
+#endif
                trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+       }
 }
 EXPORT_SYMBOL(__local_bh_disable_ip);
 #endif /* CONFIG_TRACE_IRQFLAGS */