We've also observed this issue on ChromeOS, it seems like it might long-standing epoll bug as it diverges from the behavior of poll. Any chance a maintainer can take a look? Thanks Brian On Fri, Apr 26, 2024 at 04:05:48PM +0800, Xuewen Yan wrote: > Now, the epoll only use wake_up() interface to wake up task. > However, sometimes, there are epoll users which want to use > the synchronous wakeup flag to hint the scheduler, such as > Android binder driver. > So add a wake_up_sync() define, and use the wake_up_sync() > when the sync is true in ep_poll_callback(). > > Co-developed-by: Jing Xia <jing.xia@xxxxxxxxxx> > Signed-off-by: Jing Xia <jing.xia@xxxxxxxxxx> > Signed-off-by: Xuewen Yan <xuewen.yan@xxxxxxxxxx> > --- > fs/eventpoll.c | 5 ++++- > include/linux/wait.h | 1 + > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/eventpoll.c b/fs/eventpoll.c > index 882b89edc52a..9b815e0a1ac5 100644 > --- a/fs/eventpoll.c > +++ b/fs/eventpoll.c > @@ -1336,7 +1336,10 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v > break; > } > } > - wake_up(&ep->wq); > + if (sync) > + wake_up_sync(&ep->wq); > + else > + wake_up(&ep->wq); > } > if (waitqueue_active(&ep->poll_wait)) > pwake++; > diff --git a/include/linux/wait.h b/include/linux/wait.h > index 8aa3372f21a0..2b322a9b88a2 100644 > --- a/include/linux/wait.h > +++ b/include/linux/wait.h > @@ -221,6 +221,7 @@ void __wake_up_pollfree(struct wait_queue_head *wq_head); > #define wake_up_all(x) __wake_up(x, TASK_NORMAL, 0, NULL) > #define wake_up_locked(x) __wake_up_locked((x), TASK_NORMAL, 1) > #define wake_up_all_locked(x) __wake_up_locked((x), TASK_NORMAL, 0) > +#define wake_up_sync(x) __wake_up_sync(x, TASK_NORMAL) > > #define wake_up_interruptible(x) __wake_up(x, TASK_INTERRUPTIBLE, 1, NULL) > #define wake_up_interruptible_nr(x, nr) __wake_up(x, TASK_INTERRUPTIBLE, nr, NULL) > -- > 2.25.1 >
