On Wed, 06 May 2015 11:29:57 +0000 (GMT) Maninder Singh <[email protected]> wrote:
> EP-F6AA0618C49C4AEDA73BFF1B39950BAB > > Hi , > > Recently shared a patch for using freezable_schedule instead of schedule in > msgrcv, > and after analysing message queuie implemntation we have realized even msgsnd > can also block, if queue is full, > So in this scenerio msgsnd sets task state as TASK_INTERRUPTIBLE and can > schedule function, similar behaviour as msgrcv. > This change is applicable for msgsnd as well. > > we have created patch for remotes/linux-next/akpm, because msgrcv patch is > already applied at this branch. > so we didnt include <linux/freezer.h> > This changelog is quite poor. It doesn't explain why the change is being made, it doesn't explain the user-visible effects which are being fixed, etc. So I threw it away and copied text from "ipc/msg.c: use freezable blocking call": One thing which isn't clear to me: *why* do we want to "Avoid waking up every thread sleeping in XXX during suspend and resume"? Suspend and resume are rare operations. Why do we care if a few threads wake up then go to sleep again? From: Maninder Singh <[email protected]> Subject: ipc/msg.c: msgsnd: use freezable blocking call Avoid waking up every thread sleeping in a msgsnd call during suspend and resume by calling a freezable blocking call. Previous patches modified the freezer to avoid sending wakeups to threads that are blocked in freezable blocking calls. This call was selected to be converted to a freezable call because it doesn't hold any locks or release any resources when interrupted that might be needed by another freezing task or a kernel driver during suspend, and is a common site where idle userspace tasks are blocked. Signed-off-by: Vaneet narang <[email protected]> Signed-off-by: Maninder Singh <[email protected]> Cc: Yogesh Gaur <[email protected]> Cc: Manjeet Pawar <[email protected]> Cc: Ajeet Yadav <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Tejun Heo <[email protected]> Signed-off-by: Andrew Morton <[email protected]> --- ipc/msg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN ipc/msg.c~ipc-msgc-msgsnd-use-freezable-blocking-call ipc/msg.c --- a/ipc/msg.c~ipc-msgc-msgsnd-use-freezable-blocking-call +++ a/ipc/msg.c @@ -673,7 +673,7 @@ long do_msgsnd(int msqid, long mtype, vo ipc_unlock_object(&msq->q_perm); rcu_read_unlock(); - schedule(); + freezable_schedule(); rcu_read_lock(); ipc_lock_object(&msq->q_perm); _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
