epoll: Add synchronous wakeup support for ep_poll_callback

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@unisoc.com>
Signed-off-by: Jing Xia <jing.xia@unisoc.com>
Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
Link: https://lore.kernel.org/r/20240426080548.8203-1-xuewen.yan@unisoc.com
Tested-by: Brian Geffon <bgeffon@google.com>
Reviewed-by: Brian Geffon <bgeffon@google.com>
Reported-by: Benoit Lize <lizeb@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 90fbab6b6f0363705222892f79e8e667340698f2..1a06e462b6efba8824456cffebad040720c4226a 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1373,7 +1373,10 @@ 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 8aa3372f21a080caf2738799700bd965fbd2198f..2b322a9b88a2bd122d30e70a3d6eaa12c5cec244 100644 (file)
--- 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)