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io_uring: fix ctx-exit io_rsrc_put_work() deadlock

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__io_rsrc_put_work() might need ->uring_lock, so nobody should wait for
rsrc nodes holding the mutex. However, that's exactly what
io_ring_ctx_free() does with io_wait_rsrc_data().

Split it into rsrc wait + dealloc, and move the first one out of the
lock.

Cc: stable@vger.kernel.org
Fixes: b60c8dce33 ("io_uring: preparation for rsrc tagging")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/0130c5c2693468173ec1afab714e0885d2c9c363.1628559783.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2021-08-10 02:44:23 +01:00 committed by Jens Axboe
parent c018db4a57
commit 43597aac1f
1 changed files with 8 additions and 7 deletions
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15
fs/io_uring.c
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@ -8652,13 +8652,10 @@ static void io_req_caches_free(struct io_ring_ctx *ctx)
mutex_unlock(&ctx->uring_lock);
}
static bool io_wait_rsrc_data(struct io_rsrc_data *data)
static void io_wait_rsrc_data(struct io_rsrc_data *data)
{
if (!data)
return false;
if (!atomic_dec_and_test(&data->refs))
if (data && !atomic_dec_and_test(&data->refs))
wait_for_completion(&data->done);
return true;
}
static void io_ring_ctx_free(struct io_ring_ctx *ctx)
@ -8670,10 +8667,14 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
ctx->mm_account = NULL;
}
/* __io_rsrc_put_work() may need uring_lock to progress, wait w/o it */
io_wait_rsrc_data(ctx->buf_data);
io_wait_rsrc_data(ctx->file_data);
mutex_lock(&ctx->uring_lock);
if (io_wait_rsrc_data(ctx->buf_data))
if (ctx->buf_data)
__io_sqe_buffers_unregister(ctx);
if (io_wait_rsrc_data(ctx->file_data))
if (ctx->file_data)
__io_sqe_files_unregister(ctx);
if (ctx->rings)
__io_cqring_overflow_flush(ctx, true);