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@xxxxxxxxxxxxxxx
Fixes: 3146cba99aa28 ("io-wq: make worker creation resilient against signals")
Reported-by: Julian Orth <ju.orth@xxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
io_uring/io-wq.c | 10 +++++++---
1 file 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 @@ static bool create_io_worker(struct io_wq *wq, int index)
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 {
--
2.44.0
