6.1-stable review patch. If anyone has any objections, please let me know.
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From: Pavel Begunkov asml.silence@gmail.com
commit 0453aad676ff99787124b9b3af4a5f59fbe808e2 upstream.
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.172063414... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- io_uring/io-wq.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -22,6 +22,7 @@ #include "io_uring.h"
#define WORKER_IDLE_TIMEOUT (5 * HZ) +#define WORKER_INIT_LIMIT 3
enum { IO_WORKER_F_UP = 1, /* up and active */ @@ -58,6 +59,7 @@ struct io_worker { unsigned long create_state; struct callback_head create_work; int create_index; + int init_retries;
union { struct rcu_head rcu; @@ -729,7 +731,7 @@ static bool io_wq_work_match_all(struct 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 @@ -737,6 +739,8 @@ static inline bool io_should_retry_threa */ if (fatal_signal_pending(current)) return false; + if (worker->init_retries++ >= WORKER_INIT_LIMIT) + return false;
switch (err) { case -EAGAIN: @@ -763,7 +767,7 @@ static void create_worker_cont(struct ca io_init_new_worker(wqe, 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_wqe_acct *acct = io_wqe_get_acct(worker);
atomic_dec(&acct->nr_running); @@ -830,7 +834,7 @@ fail: tsk = create_io_thread(io_wqe_worker, worker, wqe->node); if (!IS_ERR(tsk)) { io_init_new_worker(wqe, 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 {