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author | Jens Axboe <axboe@kernel.dk> | 2022-11-20 10:13:44 -0700 |
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committer | Jens Axboe <axboe@kernel.dk> | 2022-11-22 06:07:55 -0700 |
commit | 03e02acda8e267a8183e1e0ed289ff1ef9cd7ed8 (patch) | |
tree | 757d06e46ed4330edf949425d3036faa8da0ffb0 /fs/eventfd.c | |
parent | caf1aeaffc3b09649a56769e559333ae2c4f1802 (diff) | |
download | linux-03e02acda8e267a8183e1e0ed289ff1ef9cd7ed8.tar.gz linux-03e02acda8e267a8183e1e0ed289ff1ef9cd7ed8.tar.bz2 linux-03e02acda8e267a8183e1e0ed289ff1ef9cd7ed8.zip |
eventfd: provide a eventfd_signal_mask() helper
This is identical to eventfd_signal(), but it allows the caller to pass
in a mask to be used for the poll wakeup key. The use case is avoiding
repeated multishot triggers if we have a dependency between eventfd and
io_uring.
If we setup an eventfd context and register that as the io_uring eventfd,
and at the same time queue a multishot poll request for the eventfd
context, then any CQE posted will repeatedly trigger the multishot request
until it terminates when the CQ ring overflows.
In preparation for io_uring detecting this circular dependency, add the
mentioned helper so that io_uring can pass in EPOLL_URING as part of the
poll wakeup key.
Cc: stable@vger.kernel.org # 6.0
[axboe: fold in !CONFIG_EVENTFD fix from Zhang Qilong]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/eventfd.c')
-rw-r--r-- | fs/eventfd.c | 37 |
1 files changed, 21 insertions, 16 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c index c0ffee99ad23..249ca6c0b784 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -43,21 +43,7 @@ struct eventfd_ctx { int id; }; -/** - * eventfd_signal - Adds @n to the eventfd counter. - * @ctx: [in] Pointer to the eventfd context. - * @n: [in] Value of the counter to be added to the eventfd internal counter. - * The value cannot be negative. - * - * This function is supposed to be called by the kernel in paths that do not - * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX - * value, and we signal this as overflow condition by returning a EPOLLERR - * to poll(2). - * - * Returns the amount by which the counter was incremented. This will be less - * than @n if the counter has overflowed. - */ -__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) +__u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, unsigned mask) { unsigned long flags; @@ -78,12 +64,31 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) n = ULLONG_MAX - ctx->count; ctx->count += n; if (waitqueue_active(&ctx->wqh)) - wake_up_locked_poll(&ctx->wqh, EPOLLIN); + wake_up_locked_poll(&ctx->wqh, EPOLLIN | mask); current->in_eventfd = 0; spin_unlock_irqrestore(&ctx->wqh.lock, flags); return n; } + +/** + * eventfd_signal - Adds @n to the eventfd counter. + * @ctx: [in] Pointer to the eventfd context. + * @n: [in] Value of the counter to be added to the eventfd internal counter. + * The value cannot be negative. + * + * This function is supposed to be called by the kernel in paths that do not + * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX + * value, and we signal this as overflow condition by returning a EPOLLERR + * to poll(2). + * + * Returns the amount by which the counter was incremented. This will be less + * than @n if the counter has overflowed. + */ +__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) +{ + return eventfd_signal_mask(ctx, n, 0); +} EXPORT_SYMBOL_GPL(eventfd_signal); static void eventfd_free_ctx(struct eventfd_ctx *ctx) |