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Subject[PATCH RT 3/2] softirq: Avoid "local_softirq_pending" messages if task is in cpu_chill()
If the softirq thread enters cpu_chill() then ->state is UNINTERRUPTIBLE
and has no ->pi_blocked_on set and so its mask is not taken into account.

->sleeping_lock is increased by cpu_chill() since it is also requried to
avoid a splat by RCU in case cpu_chill() is used while a RCU-read lock
is held. Use the same mechanism for the softirq-pending check.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/softirq.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 48ae7dae81b9c..25bcf2f2714ba 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -105,9 +105,12 @@ static bool softirq_check_runner_tsk(struct task_struct *tsk,
* _before_ it sets pi_blocked_on to NULL under
* tsk->pi_lock. So we need to check for both: state
* and pi_blocked_on.
+ * The test against UNINTERRUPTIBLE + ->sleeping_lock is in case the
+ * task does cpu_chill().
*/
raw_spin_lock(&tsk->pi_lock);
- if (tsk->pi_blocked_on || tsk->state == TASK_RUNNING) {
+ if (tsk->pi_blocked_on || tsk->state == TASK_RUNNING ||
+ (tsk->state == TASK_UNINTERRUPTIBLE && tsk->sleeping_lock)) {
/* Clear all bits pending in that task */
*pending &= ~(tsk->softirqs_raised);
ret = true;
--
2.20.1
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