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pidfd_poll: report POLLHUP when pid_task() == NULL

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Add another wake_up_all(wait_pidfd) into __change_pid() and change
pidfd_poll() to include EPOLLHUP if task == NULL.

This allows to wait until the target process/thread is reaped.

TODO: change do_notify_pidfd() to use the keyed wakeups.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240202131226.GA26018@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Oleg Nesterov
2024-02-02 14:12:26 +01:00
committed by Christian Brauner
parent 64bef697d3
commit 43f0df54c9
2 changed files with 12 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/fork.c
+7 -15
View File
@@ -2071,20 +2071,6 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
}
#endif
static bool pidfd_task_exited(struct pid *pid, bool thread)
{
struct task_struct *task;
bool exited;
rcu_read_lock();
task = pid_task(pid, PIDTYPE_PID);
exited = !task ||
(READ_ONCE(task->exit_state) && (thread || thread_group_empty(task)));
rcu_read_unlock();
return exited;
}
/*
* Poll support for process exit notification.
*/
@@ -2092,6 +2078,7 @@ static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
{
struct pid *pid = file->private_data;
bool thread = file->f_flags & PIDFD_THREAD;
struct task_struct *task;
__poll_t poll_flags = 0;
poll_wait(file, &pid->wait_pidfd, pts);
@@ -2099,8 +2086,13 @@ static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts)
* Depending on PIDFD_THREAD, inform pollers when the thread
* or the whole thread-group exits.
*/
if (pidfd_task_exited(pid, thread))
rcu_read_lock();
task = pid_task(pid, PIDTYPE_PID);
if (!task)
poll_flags = EPOLLIN | EPOLLRDNORM | EPOLLHUP;
else if (task->exit_state && (thread || thread_group_empty(task)))
poll_flags = EPOLLIN | EPOLLRDNORM;
rcu_read_unlock();
return poll_flags;
}
kernel/pid.c
+5
View File
@@ -349,6 +349,11 @@ static void __change_pid(struct task_struct *task, enum pid_type type,
hlist_del_rcu(&task->pid_links[type]);
*pid_ptr = new;
if (type == PIDTYPE_PID) {
WARN_ON_ONCE(pid_has_task(pid, PIDTYPE_PID));
wake_up_all(&pid->wait_pidfd);
}
for (tmp = PIDTYPE_MAX; --tmp >= 0; )
if (pid_has_task(pid, tmp))
return;