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| author | Pavel Begunkov <asml.silence@gmail.com> | 2024-07-10 18:58:17 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-07-11 01:51:44 -0600 |
| commit | 0453aad676ff99787124b9b3af4a5f59fbe808e2 (patch) | |
| tree | 7e3717e964d83a91e7abb2d47295590663e31af9 /io_uring | |
| parent | f7c696a56cc7d70515774a24057b473757ec6089 (diff) | |
| download | lwn-0453aad676ff99787124b9b3af4a5f59fbe808e2.tar.gz lwn-0453aad676ff99787124b9b3af4a5f59fbe808e2.zip | |
io_uring/io-wq: limit retrying worker initialisation
If io-wq worker creation fails, we retry it by queueing up a task_work.
tasK_work is needed because it should be done from the user process
context. The problem is that retries are not limited, and if queueing a
task_work is the reason for the failure, we might get into an infinite
loop.
It doesn't seem to happen now but it would with the following patch
executing task_work in the freezer's loop. For now, arbitrarily limit the
number of attempts to create a worker.
Cc: stable@vger.kernel.org
Fixes: 3146cba99aa28 ("io-wq: make worker creation resilient against signals")
Reported-by: Julian Orth <ju.orth@gmail.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8280436925db88448c7c85c6656edee1a43029ea.1720634146.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/io-wq.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 913c92249522..f1e7c670add8 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -23,6 +23,7 @@ #include "io_uring.h" #define WORKER_IDLE_TIMEOUT (5 * HZ) +#define WORKER_INIT_LIMIT 3 enum { IO_WORKER_F_UP = 0, /* up and active */ @@ -58,6 +59,7 @@ struct io_worker { unsigned long create_state; struct callback_head create_work; + int init_retries; union { struct rcu_head rcu; @@ -745,7 +747,7 @@ static bool io_wq_work_match_all(struct io_wq_work *work, void *data) return true; } -static inline bool io_should_retry_thread(long err) +static inline bool io_should_retry_thread(struct io_worker *worker, long err) { /* * Prevent perpetual task_work retry, if the task (or its group) is @@ -753,6 +755,8 @@ static inline bool io_should_retry_thread(long err) */ if (fatal_signal_pending(current)) return false; + if (worker->init_retries++ >= WORKER_INIT_LIMIT) + return false; switch (err) { case -EAGAIN: @@ -779,7 +783,7 @@ static void create_worker_cont(struct callback_head *cb) io_init_new_worker(wq, worker, tsk); io_worker_release(worker); return; - } else if (!io_should_retry_thread(PTR_ERR(tsk))) { + } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) { struct io_wq_acct *acct = io_wq_get_acct(worker); atomic_dec(&acct->nr_running); @@ -846,7 +850,7 @@ fail: tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE); if (!IS_ERR(tsk)) { io_init_new_worker(wq, worker, tsk); - } else if (!io_should_retry_thread(PTR_ERR(tsk))) { + } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) { kfree(worker); goto fail; } else { |