diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/io_uring.c | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 24bbe3cb7ad4..36f04d0b197b 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -805,11 +805,34 @@ static void io_iopoll_reap_events(struct io_ring_ctx *ctx) static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, long min) { - int ret = 0; + int iters, ret = 0; + + /* + * We disallow the app entering submit/complete with polling, but we + * still need to lock the ring to prevent racing with polled issue + * that got punted to a workqueue. + */ + mutex_lock(&ctx->uring_lock); + iters = 0; do { int tmin = 0; + /* + * If a submit got punted to a workqueue, we can have the + * application entering polling for a command before it gets + * issued. That app will hold the uring_lock for the duration + * of the poll right here, so we need to take a breather every + * now and then to ensure that the issue has a chance to add + * the poll to the issued list. Otherwise we can spin here + * forever, while the workqueue is stuck trying to acquire the + * very same mutex. + */ + if (!(++iters & 7)) { + mutex_unlock(&ctx->uring_lock); + mutex_lock(&ctx->uring_lock); + } + if (*nr_events < min) tmin = min - *nr_events; @@ -819,6 +842,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events, ret = 0; } while (min && !*nr_events && !need_resched()); + mutex_unlock(&ctx->uring_lock); return ret; } @@ -2280,15 +2304,7 @@ static int io_sq_thread(void *data) unsigned nr_events = 0; if (ctx->flags & IORING_SETUP_IOPOLL) { - /* - * We disallow the app entering submit/complete - * with polling, but we still need to lock the - * ring to prevent racing with polled issue - * that got punted to a workqueue. - */ - mutex_lock(&ctx->uring_lock); io_iopoll_check(ctx, &nr_events, 0); - mutex_unlock(&ctx->uring_lock); } else { /* * Normal IO, just pretend everything completed. @@ -3190,9 +3206,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit, min_complete = min(min_complete, ctx->cq_entries); if (ctx->flags & IORING_SETUP_IOPOLL) { - mutex_lock(&ctx->uring_lock); ret = io_iopoll_check(ctx, &nr_events, min_complete); - mutex_unlock(&ctx->uring_lock); } else { ret = io_cqring_wait(ctx, min_complete, sig, sigsz); } |