[PATCH V2] libcfs: Fix a sleep-in-atomic bug in cfs_wi_exit

[PATCH V2] libcfs: Fix a sleep-in-atomic bug in cfs_wi_exit

[Jia-Ju Bai]

The driver may sleep under a spin lock, and the function call path is:
cfs_wi_exit (acquire the lock by spin_lock)
  LASSERT
    lbug_with_loc
      libcfs_debug_dumplog
        schedule and kthread_run --> may sleep

To fix it, all "LASSERT" is placed out of the spin_lock and spin_unlock.

Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
---
 drivers/staging/lustre/lnet/libcfs/workitem.c |   13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/lustre/lnet/libcfs/workitem.c b/drivers/staging/lustre/lnet/libcfs/workitem.c
index dbc2a9b..928d06d 100644
--- a/drivers/staging/lustre/lnet/libcfs/workitem.c
+++ b/drivers/staging/lustre/lnet/libcfs/workitem.c
@@ -111,22 +111,23 @@ struct cfs_wi_sched {
 {
 	LASSERT(!in_interrupt()); /* because we use plain spinlock */
 	LASSERT(!sched->ws_stopping);
+	LASSERT(wi->wi_running);
+	if (wi->wi_scheduled) {
+		LASSERT(!list_empty(&wi->wi_list));
+		LASSERT(sched->ws_nscheduled > 0);
+	}
 
 	spin_lock(&sched->ws_lock);
 
-	LASSERT(wi->wi_running);
 	if (wi->wi_scheduled) { /* cancel pending schedules */
-		LASSERT(!list_empty(&wi->wi_list));
 		list_del_init(&wi->wi_list);
-
-		LASSERT(sched->ws_nscheduled > 0);
 		sched->ws_nscheduled--;
 	}
 
-	LASSERT(list_empty(&wi->wi_list));
-
 	wi->wi_scheduled = 1; /* LBUG future schedule attempts */
 	spin_unlock(&sched->ws_lock);
+
+	LASSERT(list_empty(&wi->wi_list));
 }
 EXPORT_SYMBOL(cfs_wi_exit);
 
-- 
1.7.9.5

Re: [PATCH V2] libcfs: Fix a sleep-in-atomic bug in cfs_wi_exit

[Oleg Drokin]

Hello!

On May 31, 2017, at 4:00 AM, Jia-Ju Bai wrote:

> The driver may sleep under a spin lock, and the function call path is:
> cfs_wi_exit (acquire the lock by spin_lock)
>  LASSERT
>    lbug_with_loc
>      libcfs_debug_dumplog
>        schedule and kthread_run --> may sleep
> 
> To fix it, all "LASSERT" is placed out of the spin_lock and spin_unlock.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
> ---
> drivers/staging/lustre/lnet/libcfs/workitem.c |   13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lnet/libcfs/workitem.c b/drivers/staging/lustre/lnet/libcfs/workitem.c
> index dbc2a9b..928d06d 100644
> --- a/drivers/staging/lustre/lnet/libcfs/workitem.c
> +++ b/drivers/staging/lustre/lnet/libcfs/workitem.c
> @@ -111,22 +111,23 @@ struct cfs_wi_sched {
> {
> 	LASSERT(!in_interrupt()); /* because we use plain spinlock */
> 	LASSERT(!sched->ws_stopping);
> +	LASSERT(wi->wi_running);
> +	if (wi->wi_scheduled) {
> +		LASSERT(!list_empty(&wi->wi_list));
> +		LASSERT(sched->ws_nscheduled > 0);
> +	}

Similarly here and in all other patches about LASSERT calls under spinlocks() from you,
just think of them as a panic() call, no operations are expected to continue
after it triggers.

Thanks.

> 
> 	spin_lock(&sched->ws_lock);
> 
> -	LASSERT(wi->wi_running);
> 	if (wi->wi_scheduled) { /* cancel pending schedules */
> -		LASSERT(!list_empty(&wi->wi_list));
> 		list_del_init(&wi->wi_list);
> -
> -		LASSERT(sched->ws_nscheduled > 0);
> 		sched->ws_nscheduled--;
> 	}
> 
> -	LASSERT(list_empty(&wi->wi_list));
> -
> 	wi->wi_scheduled = 1; /* LBUG future schedule attempts */
> 	spin_unlock(&sched->ws_lock);
> +
> +	LASSERT(list_empty(&wi->wi_list));
> }
> EXPORT_SYMBOL(cfs_wi_exit);
> 
> -- 
> 1.7.9.5
> 

Re: [PATCH V2] libcfs: Fix a sleep-in-atomic bug in cfs_wi_exit

[Greg KH]

On Wed, May 31, 2017 at 04:00:41PM +0800, Jia-Ju Bai wrote:
> The driver may sleep under a spin lock, and the function call path is:
> cfs_wi_exit (acquire the lock by spin_lock)
>   LASSERT
>     lbug_with_loc
>       libcfs_debug_dumplog
>         schedule and kthread_run --> may sleep
> 
> To fix it, all "LASSERT" is placed out of the spin_lock and spin_unlock.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
> ---
>  drivers/staging/lustre/lnet/libcfs/workitem.c |   13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)

What changed from v1?  You have to always tell us that.

Please redo all of these, if they are still valid patches, and send them
as a patch series, so I know what order they should be applied in.

thanks,

greg k-h