在 2021/2/4 上午12:45, Pavel Begunkov 写道:
On 03/02/2021 16:35, Pavel Begunkov wrote:
On 03/02/2021 14:57, Hao Xu wrote:
This is caused by calling io_run_task_work_sig() to do work under
uring_lock while the caller io_sqe_files_unregister() already held
uring_lock.
we need to check if uring_lock is held by us when doing unlock around
io_run_task_work_sig() since there are code paths down to that place
without uring_lock held.
1. we don't want to allow parallel io_sqe_files_unregister()s
happening, it's synchronised by uring_lock atm. Otherwise it's
buggy.
Here "since there are code paths down to that place without uring_lock
held" I mean code path of io_ring_ctx_free().
This one should be simple, alike to
if (percpu_refs_is_dying())
return error; // fail *files_unregister();
2. probably same with unregister and submit.
Reported-by: Abaci <abaci@xxxxxxxxxxxxxxxxx>
Fixes: 1ffc54220c44 ("io_uring: fix io_sqe_files_unregister() hangs")
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index efb6d02fea6f..b093977713ee 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7362,18 +7362,25 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx, bool locked)
/* wait for all refs nodes to complete */
flush_delayed_work(&ctx->file_put_work);
+ if (locked)
+ mutex_unlock(&ctx->uring_lock);
do {
ret = wait_for_completion_interruptible(&data->done);
if (!ret)
break;
ret = io_run_task_work_sig();
- if (ret < 0) {
- percpu_ref_resurrect(&data->refs);
- reinit_completion(&data->done);
- io_sqe_files_set_node(data, backup_node);
- return ret;
- }
+ if (ret < 0)
+ break;
} while (1);
+ if (locked)
+ mutex_lock(&ctx->uring_lock);
+
+ if (ret < 0) {
+ percpu_ref_resurrect(&data->refs);
+ reinit_completion(&data->done);
+ io_sqe_files_set_node(data, backup_node);
+ return ret;
+ }
__io_sqe_files_unregister(ctx);
nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE);
