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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1654943518; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=XiEUBihp1TklQygOb5R5MwUB6ZpxGvauMVAboxJDCUQ=; b=UVWjkHFzL9Nm3iIUAybHTIVj9fDk7wsxKbXSpi9UYCWnFVcHgQv6QEVNr5cG2elTANksYx 64YMd1+BSK0W+51B5cKzuGt8F0Ob/My9kCjcylYtlwR8qtXXqkotCq/AeI+Z+vW4l4hNzN X638gE7b57dwiTZaa3+T339dcydWcTk= From: Hao Xu To: io-uring@vger.kernel.org Cc: Jens Axboe , Pavel Begunkov Subject: [PATCH v4] io_uring: switch cancel_hash to use per entry spinlock Date: Sat, 11 Jun 2022 18:31:49 +0800 Message-Id: <20220611103149.925423-1-hao.xu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org From: Hao Xu Add a new io_hash_bucket structure so that each bucket in cancel_hash has separate spinlock. Use per entry lock for cancel_hash, this removes some completion lock invocation and remove contension between different cancel_hash entries. Signed-off-by: Hao Xu --- v1->v2: - Add per entry lock for poll/apoll task work code which was missed in v1 - add an member in io_kiocb to track req's indice in cancel_hash v2->v3: - make struct io_hash_bucket align with cacheline to avoid cacheline false sharing. - re-calculate hash value when deleting an entry from cancel_hash. (cannot leverage struct io_poll to store the indice since it's already 64 Bytes) v3->v4: - address race issue in cancellation path per Pavel's comment - remove the inline decorator io_uring/cancel.c | 14 ++++++- io_uring/cancel.h | 6 +++ io_uring/fdinfo.c | 9 +++-- io_uring/io_uring.c | 8 ++-- io_uring/io_uring_types.h | 2 +- io_uring/poll.c | 80 ++++++++++++++++++++++++--------------- 6 files changed, 79 insertions(+), 40 deletions(-) diff --git a/io_uring/cancel.c b/io_uring/cancel.c index 83cceb52d82d..6f2888388a40 100644 --- a/io_uring/cancel.c +++ b/io_uring/cancel.c @@ -93,14 +93,14 @@ int io_try_cancel(struct io_kiocb *req, struct io_cancel_data *cd) if (!ret) return 0; - spin_lock(&ctx->completion_lock); ret = io_poll_cancel(ctx, cd); if (ret != -ENOENT) goto out; + spin_lock(&ctx->completion_lock); if (!(cd->flags & IORING_ASYNC_CANCEL_FD)) ret = io_timeout_cancel(ctx, cd); -out: spin_unlock(&ctx->completion_lock); +out: return ret; } @@ -192,3 +192,13 @@ int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags) io_req_set_res(req, ret, 0); return IOU_OK; } + +void init_hash_table(struct io_hash_bucket *hash_table, unsigned size) +{ + unsigned int i; + + for (i = 0; i < size; i++) { + spin_lock_init(&hash_table[i].lock); + INIT_HLIST_HEAD(&hash_table[i].list); + } +} diff --git a/io_uring/cancel.h b/io_uring/cancel.h index 4f35d8696325..556a7dcf160e 100644 --- a/io_uring/cancel.h +++ b/io_uring/cancel.h @@ -4,3 +4,9 @@ int io_async_cancel_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags); int io_try_cancel(struct io_kiocb *req, struct io_cancel_data *cd); +void init_hash_table(struct io_hash_bucket *hash_table, unsigned size); + +struct io_hash_bucket { + spinlock_t lock; + struct hlist_head list; +} ____cacheline_aligned_in_smp; diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c index fcedde4b4b1e..f941c73f5502 100644 --- a/io_uring/fdinfo.c +++ b/io_uring/fdinfo.c @@ -13,6 +13,7 @@ #include "io_uring.h" #include "sqpoll.h" #include "fdinfo.h" +#include "cancel.h" #ifdef CONFIG_PROC_FS static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id, @@ -157,17 +158,19 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, mutex_unlock(&ctx->uring_lock); seq_puts(m, "PollList:\n"); - spin_lock(&ctx->completion_lock); for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) { - struct hlist_head *list = &ctx->cancel_hash[i]; + struct io_hash_bucket *hb = &ctx->cancel_hash[i]; struct io_kiocb *req; - hlist_for_each_entry(req, list, hash_node) + spin_lock(&hb->lock); + hlist_for_each_entry(req, &hb->list, hash_node) seq_printf(m, " op=%d, task_works=%d\n", req->opcode, task_work_pending(req->task)); + spin_unlock(&hb->lock); } seq_puts(m, "CqOverflowList:\n"); + spin_lock(&ctx->completion_lock); list_for_each_entry(ocqe, &ctx->cq_overflow_list, list) { struct io_uring_cqe *cqe = &ocqe->cqe; diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 1572ebe3cff1..b67ab76b9e56 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -725,11 +725,13 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p) if (hash_bits <= 0) hash_bits = 1; ctx->cancel_hash_bits = hash_bits; - ctx->cancel_hash = kmalloc((1U << hash_bits) * sizeof(struct hlist_head), - GFP_KERNEL); + ctx->cancel_hash = + kmalloc((1U << hash_bits) * sizeof(struct io_hash_bucket), + GFP_KERNEL); if (!ctx->cancel_hash) goto err; - __hash_init(ctx->cancel_hash, 1U << hash_bits); + + init_hash_table(ctx->cancel_hash, 1U << hash_bits); ctx->dummy_ubuf = kzalloc(sizeof(*ctx->dummy_ubuf), GFP_KERNEL); if (!ctx->dummy_ubuf) diff --git a/io_uring/io_uring_types.h b/io_uring/io_uring_types.h index 7c22cf35a7e2..b67843a5f3b6 100644 --- a/io_uring/io_uring_types.h +++ b/io_uring/io_uring_types.h @@ -230,7 +230,7 @@ struct io_ring_ctx { * manipulate the list, hence no extra locking is needed there. */ struct io_wq_work_list iopoll_list; - struct hlist_head *cancel_hash; + struct io_hash_bucket *cancel_hash; unsigned cancel_hash_bits; bool poll_multi_queue; diff --git a/io_uring/poll.c b/io_uring/poll.c index 0df5eca93b16..bc93a89185f8 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -19,6 +19,7 @@ #include "opdef.h" #include "kbuf.h" #include "poll.h" +#include "cancel.h" struct io_poll_update { struct file *file; @@ -73,10 +74,22 @@ static struct io_poll *io_poll_get_single(struct io_kiocb *req) static void io_poll_req_insert(struct io_kiocb *req) { struct io_ring_ctx *ctx = req->ctx; - struct hlist_head *list; + u32 index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits); + struct io_hash_bucket *hb = &ctx->cancel_hash[index]; - list = &ctx->cancel_hash[hash_long(req->cqe.user_data, ctx->cancel_hash_bits)]; - hlist_add_head(&req->hash_node, list); + spin_lock(&hb->lock); + hlist_add_head(&req->hash_node, &hb->list); + spin_unlock(&hb->lock); +} + +static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx) +{ + u32 index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits); + spinlock_t *lock = &ctx->cancel_hash[index].lock; + + spin_lock(lock); + hash_del(&req->hash_node); + spin_unlock(lock); } static void io_init_poll_iocb(struct io_poll *poll, __poll_t events, @@ -220,8 +233,8 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked) } io_poll_remove_entries(req); + io_poll_req_delete(req, ctx); spin_lock(&ctx->completion_lock); - hash_del(&req->hash_node); req->cqe.flags = 0; __io_req_complete_post(req); io_commit_cqring(ctx); @@ -231,7 +244,6 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked) static void io_apoll_task_func(struct io_kiocb *req, bool *locked) { - struct io_ring_ctx *ctx = req->ctx; int ret; ret = io_poll_check_events(req, locked); @@ -239,9 +251,7 @@ static void io_apoll_task_func(struct io_kiocb *req, bool *locked) return; io_poll_remove_entries(req); - spin_lock(&ctx->completion_lock); - hash_del(&req->hash_node); - spin_unlock(&ctx->completion_lock); + io_poll_req_delete(req, req->ctx); if (!ret) io_req_task_submit(req, locked); @@ -435,9 +445,7 @@ static int __io_arm_poll_handler(struct io_kiocb *req, return 0; } - spin_lock(&ctx->completion_lock); io_poll_req_insert(req); - spin_unlock(&ctx->completion_lock); if (mask && (poll->events & EPOLLET)) { /* can't multishot if failed, just queue the event we've got */ @@ -534,32 +542,31 @@ __cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk, bool found = false; int i; - spin_lock(&ctx->completion_lock); for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) { - struct hlist_head *list; + struct io_hash_bucket *hb = &ctx->cancel_hash[i]; - list = &ctx->cancel_hash[i]; - hlist_for_each_entry_safe(req, tmp, list, hash_node) { + spin_lock(&hb->lock); + hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) { if (io_match_task_safe(req, tsk, cancel_all)) { hlist_del_init(&req->hash_node); io_poll_cancel_req(req); found = true; } } + spin_unlock(&hb->lock); } - spin_unlock(&ctx->completion_lock); return found; } static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only, struct io_cancel_data *cd) - __must_hold(&ctx->completion_lock) { - struct hlist_head *list; struct io_kiocb *req; + u32 index = hash_long(cd->data, ctx->cancel_hash_bits); + struct io_hash_bucket *hb = &ctx->cancel_hash[index]; - list = &ctx->cancel_hash[hash_long(cd->data, ctx->cancel_hash_bits)]; - hlist_for_each_entry(req, list, hash_node) { + spin_lock(&hb->lock); + hlist_for_each_entry(req, &hb->list, hash_node) { if (cd->data != req->cqe.user_data) continue; if (poll_only && req->opcode != IORING_OP_POLL_ADD) @@ -571,21 +578,21 @@ static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only, } return req; } + spin_unlock(&hb->lock); return NULL; } static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx, struct io_cancel_data *cd) - __must_hold(&ctx->completion_lock) { struct io_kiocb *req; int i; for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) { - struct hlist_head *list; + struct io_hash_bucket *hb = &ctx->cancel_hash[i]; - list = &ctx->cancel_hash[i]; - hlist_for_each_entry(req, list, hash_node) { + spin_lock(&hb->lock); + hlist_for_each_entry(req, &hb->list, hash_node) { if (!(cd->flags & IORING_ASYNC_CANCEL_ANY) && req->file != cd->file) continue; @@ -594,12 +601,12 @@ static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx, req->work.cancel_seq = cd->seq; return req; } + spin_unlock(&hb->lock); } return NULL; } static bool io_poll_disarm(struct io_kiocb *req) - __must_hold(&ctx->completion_lock) { if (!io_poll_get_ownership(req)) return false; @@ -609,17 +616,23 @@ static bool io_poll_disarm(struct io_kiocb *req) } int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd) - __must_hold(&ctx->completion_lock) { struct io_kiocb *req; + u32 index; + spinlock_t *lock; if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_ANY)) req = io_poll_file_find(ctx, cd); else req = io_poll_find(ctx, false, cd); - if (!req) + if (!req) { return -ENOENT; + } else { + index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits); + lock = &ctx->cancel_hash[index].lock; + } io_poll_cancel_req(req); + spin_unlock(lock); return 0; } @@ -714,18 +727,23 @@ int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags) struct io_poll_update *poll_update = io_kiocb_to_cmd(req); struct io_cancel_data cd = { .data = poll_update->old_user_data, }; struct io_ring_ctx *ctx = req->ctx; + u32 index = hash_long(cd.data, ctx->cancel_hash_bits); + spinlock_t *lock = &ctx->cancel_hash[index].lock; struct io_kiocb *preq; int ret2, ret = 0; bool locked; - spin_lock(&ctx->completion_lock); preq = io_poll_find(ctx, true, &cd); - if (!preq || !io_poll_disarm(preq)) { - spin_unlock(&ctx->completion_lock); - ret = preq ? -EALREADY : -ENOENT; + if (!preq) { + ret = -ENOENT; + goto out; + } + ret2 = io_poll_disarm(preq); + spin_unlock(lock); + if (!ret2) { + ret = -EALREADY; goto out; } - spin_unlock(&ctx->completion_lock); if (poll_update->update_events || poll_update->update_user_data) { /* only mask one event flags, keep behavior flags */ base-commit: d8271bf021438f468dab3cd84fe5279b5bbcead8 -- 2.25.1