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io_uring: delay sqarray static branch disablement

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io_key_has_sqarray static branch can be easily switched on/off by the
user every time patching the kernel. That can be very disruptive as it
might require heavy synchronisation across all CPUs. Use deferred static
keys, which can rate-limit it by deferring, batching and potentially
effectively eliminating dec+inc pairs.

Fixes: 9b296c625a ("io_uring: static_key for !IORING_SETUP_NO_SQARRAY")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2026-02-15 22:06:52 +00:00 • committed by Jens Axboe
parent 6b34f8edf8
commit 56112578c7
1 changed files with 4 additions and 4 deletions
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8
io_uring/io_uring.c
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@ -119,7 +119,7 @@
static void io_queue_sqe(struct io_kiocb *req, unsigned int extra_flags);
static void __io_req_caches_free(struct io_ring_ctx *ctx);
static __read_mostly DEFINE_STATIC_KEY_FALSE(io_key_has_sqarray);
static __read_mostly DEFINE_STATIC_KEY_DEFERRED_FALSE(io_key_has_sqarray, HZ);
struct kmem_cache *req_cachep;
static struct workqueue_struct *iou_wq __ro_after_init;
@ -1978,7 +1978,7 @@ static bool io_get_sqe(struct io_ring_ctx *ctx, const struct io_uring_sqe **sqe)
unsigned mask = ctx->sq_entries - 1;
unsigned head = ctx->cached_sq_head++ & mask;
if (static_branch_unlikely(&io_key_has_sqarray) &&
if (static_branch_unlikely(&io_key_has_sqarray.key) &&
(!(ctx->flags & IORING_SETUP_NO_SQARRAY))) {
head = READ_ONCE(ctx->sq_array[head]);
if (unlikely(head >= ctx->sq_entries)) {
@ -2173,7 +2173,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
io_rings_free(ctx);
if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
static_branch_dec(&io_key_has_sqarray);
static_branch_slow_dec_deferred(&io_key_has_sqarray);
percpu_ref_exit(&ctx->refs);
free_uid(ctx->user);
@ -2946,7 +2946,7 @@ static __cold int io_uring_create(struct io_ctx_config *config)
ctx->clock_offset = 0;
if (!(ctx->flags & IORING_SETUP_NO_SQARRAY))
static_branch_inc(&io_key_has_sqarray);
static_branch_deferred_inc(&io_key_has_sqarray);
if ((ctx->flags & IORING_SETUP_DEFER_TASKRUN) &&
!(ctx->flags & IORING_SETUP_IOPOLL))