[PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[Oleg Nesterov]

rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
POLLHUP-only waiters which wait for pid_task() == NULL.

TODO:
    - as Christian pointed out, this asks for the new wake_up_all_poll()
      helper, it can already have other users.

    - we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
      waiters, but this needs more work.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/signal.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 9b40109f0c56..c3fac06937e2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2021,11 +2021,12 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
 
 void do_notify_pidfd(struct task_struct *task)
 {
-	struct pid *pid;
+	struct pid *pid = task_pid(task);
 
 	WARN_ON(task->exit_state == 0);
-	pid = task_pid(task);
-	wake_up_all(&pid->wait_pidfd);
+
+	__wake_up(&pid->wait_pidfd, TASK_NORMAL, 0,
+			poll_to_key(EPOLLIN | EPOLLRDNORM));
 }
 
 /*
-- 
2.25.1.362.g51ebf55

Re: [PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[Oleg Nesterov]

Argh, sorry for noise Christian, I have sent the same patch twice.

Please ignore this email, the next email from me with the same
subject adds the reference to our discussion into the changelog.

On 02/05, Oleg Nesterov wrote:
>
> rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
> POLLHUP-only waiters which wait for pid_task() == NULL.
> 
> TODO:
>     - as Christian pointed out, this asks for the new wake_up_all_poll()
>       helper, it can already have other users.
> 
>     - we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
>       waiters, but this needs more work.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
>  kernel/signal.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 9b40109f0c56..c3fac06937e2 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2021,11 +2021,12 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
>  
>  void do_notify_pidfd(struct task_struct *task)
>  {
> -	struct pid *pid;
> +	struct pid *pid = task_pid(task);
>  
>  	WARN_ON(task->exit_state == 0);
> -	pid = task_pid(task);
> -	wake_up_all(&pid->wait_pidfd);
> +
> +	__wake_up(&pid->wait_pidfd, TASK_NORMAL, 0,
> +			poll_to_key(EPOLLIN | EPOLLRDNORM));
>  }
>  
>  /*
> -- 
> 2.25.1.362.g51ebf55
> 
> 

[PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[Oleg Nesterov]

rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
POLLHUP-only waiters which wait for pid_task() == NULL.

TODO:
    - as Christian pointed out, this asks for the new wake_up_all_poll()
      helper, it can already have other users.

    - we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
      waiters, but this needs more work. See
      https://lore.kernel.org/all/20240205140848.GA15853@redhat.com/

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/signal.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 9b40109f0c56..c3fac06937e2 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2021,11 +2021,12 @@ int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)
 
 void do_notify_pidfd(struct task_struct *task)
 {
-	struct pid *pid;
+	struct pid *pid = task_pid(task);
 
 	WARN_ON(task->exit_state == 0);
-	pid = task_pid(task);
-	wake_up_all(&pid->wait_pidfd);
+
+	__wake_up(&pid->wait_pidfd, TASK_NORMAL, 0,
+			poll_to_key(EPOLLIN | EPOLLRDNORM));
 }
 
 /*
-- 
2.25.1.362.g51ebf55

Re: [PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[Christian Brauner]

On Mon, 05 Feb 2024 15:13:48 +0100, Oleg Nesterov wrote:
> rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
> POLLHUP-only waiters which wait for pid_task() == NULL.
> 
> TODO:
>     - as Christian pointed out, this asks for the new wake_up_all_poll()
>       helper, it can already have other users.
> 
> [...]

Applied to the vfs.pidfd branch of the vfs/vfs.git tree.
Patches in the vfs.pidfd branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.pidfd

[1/1] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))
      https://git.kernel.org/vfs/vfs/c/e1358f104c9e

Re: [PATCH] pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))

[Tycho Andersen]

On Mon, Feb 05, 2024 at 03:13:48PM +0100, Oleg Nesterov wrote:
> rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
> POLLHUP-only waiters which wait for pid_task() == NULL.
> 
> TODO:
>     - as Christian pointed out, this asks for the new wake_up_all_poll()
>       helper, it can already have other users.
> 
>     - we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
>       waiters, but this needs more work. See
>       https://lore.kernel.org/all/20240205140848.GA15853@redhat.com/
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Reviewed-by: Tycho Andersen <tandersen@netflix.com>