[tip:locking/core] softirq/preempt: Add missing current-> preempt_disable_ip update

[tip-bot for Heiko Carstens]

Commit-ID:  0f1ba9a2cea52896448ef4e14a4cb1880b8e5bee
Gitweb:     http://git.kernel.org/tip/0f1ba9a2cea52896448ef4e14a4cb1880b8e5bee
Author:     Heiko Carstens <heiko.carstens@xxxxxxxxxx>
AuthorDate: Wed, 7 Jan 2015 10:04:41 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 14 Jan 2015 15:16:21 +0100

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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150107090441.GC4365@osiris
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/softirq.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 501baa9..b9ae816 100644
--- 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 */
--
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