Merge tag 'pidfd-updates-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/braun...

[sfrench/cifs-2.6.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index 847dd147b06899ad7efb51be5df850b6db631856..187c02ce534c87a955cf93d1d01f9fba57c723e2 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1711,8 +1711,34 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)
 }
 #endif
 
+/*
+ * Poll support for process exit notification.
+ */
+static unsigned int pidfd_poll(struct file *file, struct poll_table_struct *pts)
+{
+       struct task_struct *task;
+       struct pid *pid = file->private_data;
+       int poll_flags = 0;
+
+       poll_wait(file, &pid->wait_pidfd, pts);
+
+       rcu_read_lock();
+       task = pid_task(pid, PIDTYPE_PID);
+       /*
+        * Inform pollers only when the whole thread group exits.
+        * If the thread group leader exits before all other threads in the
+        * group, then poll(2) should block, similar to the wait(2) family.
+        */
+       if (!task || (task->exit_state && thread_group_empty(task)))
+               poll_flags = POLLIN | POLLRDNORM;
+       rcu_read_unlock();
+
+       return poll_flags;
+}
+
 const struct file_operations pidfd_fops = {
        .release = pidfd_release,
+       .poll = pidfd_poll,
 #ifdef CONFIG_PROC_FS
        .show_fdinfo = pidfd_show_fdinfo,
 #endif