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io_uring: never run tw and fallback in parallel 

Once we fallback a tw we want all requests to that task to be given to
the fallback wq so we dont run it in parallel with the last, i.e. post
PF_EXITING, tw run of the task.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/96f4987265c4312f376f206511c6af3e77aaf5ac.1670384893.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2022-12-07 03:53:33 +00:00 committed by Jens Axboe
parent d34b1b0b67
commit 77e443ab29
1 changed files with 10 additions and 2 deletions
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12
io_uring/io_uring.c
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@ -149,6 +149,7 @@ static void io_clean_op(struct io_kiocb *req);
static void io_queue_sqe(struct io_kiocb *req);
static void io_move_task_work_from_local(struct io_ring_ctx *ctx);
static void __io_submit_flush_completions(struct io_ring_ctx *ctx);
static __cold void io_fallback_tw(struct io_uring_task *tctx);
static struct kmem_cache *req_cachep;
@ -1149,10 +1150,17 @@ void tctx_task_work(struct callback_head *cb)
struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
task_work);
struct llist_node fake = {};
struct llist_node *node = io_llist_xchg(&tctx->task_list, &fake);
struct llist_node *node;
unsigned int loops = 1;
unsigned int count = handle_tw_list(node, &ctx, &uring_locked, NULL);
unsigned int count;
if (unlikely(current->flags & PF_EXITING)) {
io_fallback_tw(tctx);
return;
}
node = io_llist_xchg(&tctx->task_list, &fake);
count = handle_tw_list(node, &ctx, &uring_locked, NULL);
node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
while (node != &fake) {
loops++;