From 390d967653e17205f0e519f691b7d6be0a05ff45 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 5 Nov 2025 00:05:01 +0100 Subject: [PATCH] pidfs: reduce wait_pidfd lock scope There's no need to hold the lock after we realized that pid->attr is set. We're holding a reference to struct pid so it won't go away and pidfs_exit() is called once per struct pid. Link: https://patch.msgid.link/20251105-work-pidfs-wait_pidfd-lock-v1-1-02638783be07@kernel.org Signed-off-by: Christian Brauner --- fs/pidfs.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/fs/pidfs.c b/fs/pidfs.c index 354ceb2126e7c..dbbdd2085790b 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -634,17 +634,19 @@ void pidfs_exit(struct task_struct *tsk) might_sleep(); - guard(spinlock_irq)(&pid->wait_pidfd.lock); - attr = pid->attr; - if (!attr) { - /* - * No one ever held a pidfd for this struct pid. - * Mark it as dead so no one can add a pidfs - * entry anymore. We're about to be reaped and - * so no exit information would be available. - */ - pid->attr = PIDFS_PID_DEAD; - return; + /* Synchronize with pidfs_register_pid(). */ + scoped_guard(spinlock_irq, &pid->wait_pidfd.lock) { + attr = pid->attr; + if (!attr) { + /* + * No one ever held a pidfd for this struct pid. + * Mark it as dead so no one can add a pidfs + * entry anymore. We're about to be reaped and + * so no exit information would be available. + */ + pid->attr = PIDFS_PID_DEAD; + return; + } } /* -- 2.47.3