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Subject[PATCH] sched.h: Annotate sighand_struct with __rcu
Date
From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>

This patch fixes the following sparse errors by annotating the
sighand_struct with __rcu

kernel/fork.c:1511:9: error: incompatible types in comparison expression
kernel/exit.c:100:19: error: incompatible types in comparison expression
kernel/signal.c:1370:27: error: incompatible types in comparison expression

This fix introduces the following sparse error in signal.c due to
checking the sighand pointer without rcu primitives:

kernel/signal.c:1386:21: error: incompatible types in comparison expression

This new sparse error is also addressed in this patch.

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
---
include/linux/sched.h | 2 +-
kernel/signal.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b511e178a89f..7a351360ad54 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -918,7 +918,7 @@ struct task_struct {

/* Signal handlers: */
struct signal_struct *signal;
- struct sighand_struct *sighand;
+ struct sighand_struct __rcu *sighand;
sigset_t blocked;
sigset_t real_blocked;
/* Restored if set_restore_sigmask() was used: */
diff --git a/kernel/signal.c b/kernel/signal.c
index bcd46f547db3..1272def37462 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1383,7 +1383,8 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
* must see ->sighand == NULL.
*/
spin_lock_irqsave(&sighand->siglock, *flags);
- if (likely(sighand == tsk->sighand))
+ if (likely(sighand == rcu_dereference_protected(tsk->sighand,
+ lockdep_is_held(&sighand->siglock))))
break;
spin_unlock_irqrestore(&sighand->siglock, *flags);
}
--
2.17.1
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