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io_uring: always lock __io_cqring_overflow_flush 

commit 8d09a88ef9d3cb7d21d45c39b7b7c31298d23998 upstream.

Conditional locking is never great, in case of
__io_cqring_overflow_flush(), which is a slow path, it's not justified.
Don't handle IOPOLL separately, always grab uring_lock for overflow
flushing.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/162947df299aa12693ac4b305dacedab32ec7976.1712708261.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pavel Begunkov 2024-04-10 02:26:54 +01:00 committed by Greg Kroah-Hartman
parent e3fb0e6afc
commit 6a91a5816b
1 changed files with 8 additions and 5 deletions
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13
io_uring/io_uring.c
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@ -667,6 +667,8 @@ static void io_cqring_overflow_kill(struct io_ring_ctx *ctx)
struct io_overflow_cqe *ocqe;
LIST_HEAD(list);
lockdep_assert_held(&ctx->uring_lock);
spin_lock(&ctx->completion_lock);
list_splice_init(&ctx->cq_overflow_list, &list);
clear_bit(IO_CHECK_CQ_OVERFLOW_BIT, &ctx->check_cq);
@ -683,6 +685,8 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx)
{
size_t cqe_size = sizeof(struct io_uring_cqe);
lockdep_assert_held(&ctx->uring_lock);
if (__io_cqring_events(ctx) == ctx->cq_entries)
return;
@ -727,12 +731,9 @@ static void __io_cqring_overflow_flush(struct io_ring_ctx *ctx)
static void io_cqring_do_overflow_flush(struct io_ring_ctx *ctx)
{
/* iopoll syncs against uring_lock, not completion_lock */
if (ctx->flags & IORING_SETUP_IOPOLL)
mutex_lock(&ctx->uring_lock);
mutex_lock(&ctx->uring_lock);
__io_cqring_overflow_flush(ctx);
if (ctx->flags & IORING_SETUP_IOPOLL)
mutex_unlock(&ctx->uring_lock);
mutex_unlock(&ctx->uring_lock);
}
static void io_cqring_overflow_flush(struct io_ring_ctx *ctx)
@ -1611,6 +1612,8 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
unsigned int nr_events = 0;
unsigned long check_cq;
lockdep_assert_held(&ctx->uring_lock);
if (!io_allowed_run_tw(ctx))
return -EEXIST;