sched.h: Annotate sighand_struct with __rcu

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 fixed in this patch.

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20200124045908.26389-1-madhuparnabhowmik10@gmail.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 467d260..ef60aa1 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -917,7 +917,7 @@ 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 bcd46f5..9ad8dea 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1383,7 +1383,7 @@ 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_access_pointer(tsk->sighand)))
                        break;
                spin_unlock_irqrestore(&sighand->siglock, *flags);
        }