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: 9b296c625ac1d ("io_uring: static_key for !IORING_SETUP_NO_SQARRAY") Signed-off-by: Pavel Begunkov --- io_uring/io_uring.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 3a2753f6b444..1e627b7a2f3a 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -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); @@ -2951,7 +2951,7 @@ 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)) -- 2.52.0