[PATCH] softirq/preempt: add missing current->preempt_disable_ip update

From: Heiko Carstens
Date: Mon Nov 24 2014 - 09:16:40 EST


While debugging some "sleeping function called from invalid context" bug I
realized that the debug message "Preemption disabled at:" pointed to an
incorrect function.
In particular if the 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>
---
kernel/softirq.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 501baa9ac1be..edd51027e3ab 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -114,8 +114,13 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
trace_softirqs_off(ip);
raw_local_irq_restore(flags);

- if (preempt_count() == cnt)
- trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+ if (preempt_count() == cnt) {
+ unsigned long ip = get_parent_ip(CALLER_ADDR1);
+#ifdef CONFIG_DEBUG_PREEMPT
+ current->preempt_disable_ip = ip;
+#endif
+ trace_preempt_off(CALLER_ADDR0, ip);
+ }
}
EXPORT_SYMBOL(__local_bh_disable_ip);
#endif /* CONFIG_TRACE_IRQFLAGS */
--
1.8.5.5

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