diff options
| author | Christian Brauner <brauner@kernel.org> | 2025-01-10 11:59:08 +0100 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-01-10 11:59:45 +0100 |
| commit | 67cd2e23c0f353803f182ae790a7d5074d4c1a4d (patch) | |
| tree | 21b4329a819a52e988be56b5faefd9a78255f896 /include/linux | |
| parent | 40384c840ea1944d7c5a392e8975ed088ecf0b37 (diff) | |
| parent | f005bf18a57aadf3af1e85a0f0151cb3688ee606 (diff) | |
Merge patch series "poll_wait: add mb() to fix theoretical race between waitqueue_active() and .poll()"
Oleg Nesterov <oleg@redhat.com> says:
The waitqueue_active() helper can only be used if both waker and waiter
have memory barriers that pair with each other. But __pollwait() is
broken in this respect. Fix it.
* patches from https://lore.kernel.org/r/20250107162649.GA18886@redhat.com:
poll: kill poll_does_not_wait()
sock_poll_wait: kill the no longer necessary barrier after poll_wait()
io_uring_poll: kill the no longer necessary barrier after poll_wait()
poll_wait: kill the obsolete wait_address check
poll_wait: add mb() to fix theoretical race between waitqueue_active() and .poll()
Link: https://lore.kernel.org/r/20250107162649.GA18886@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/poll.h | 26 |
1 files changed, 12 insertions, 14 deletions
diff --git a/include/linux/poll.h b/include/linux/poll.h index d1ea4f3714a8..12bb18e8b978 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -25,14 +25,14 @@ struct poll_table_struct; -/* +/* * structures and helpers for f_op->poll implementations */ typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *); /* - * Do not touch the structure directly, use the access functions - * poll_does_not_wait() and poll_requested_events() instead. + * Do not touch the structure directly, use the access function + * poll_requested_events() instead. */ typedef struct poll_table_struct { poll_queue_proc _qproc; @@ -41,18 +41,16 @@ typedef struct poll_table_struct { static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p) { - if (p && p->_qproc && wait_address) + if (p && p->_qproc) { p->_qproc(filp, wait_address, p); -} - -/* - * Return true if it is guaranteed that poll will not wait. This is the case - * if the poll() of another file descriptor in the set got an event, so there - * is no need for waiting. - */ -static inline bool poll_does_not_wait(const poll_table *p) -{ - return p == NULL || p->_qproc == NULL; + /* + * This memory barrier is paired in the wq_has_sleeper(). + * See the comment above prepare_to_wait(), we need to + * ensure that subsequent tests in this thread can't be + * reordered with __add_wait_queue() in _qproc() paths. + */ + smp_mb(); + } } /* |