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io_uring: use io-wq manager as backup task if task is exiting

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If the original task is (or has) exited, then the task work will not get
queued properly. Allow for using the io-wq manager task to queue this
work for execution, and ensure that the io-wq manager notices and runs
this work if woken up (or exiting).

Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-04-03 11:26:26 -06:00
parent 3537b6a7c6
commit aa96bf8a9e
3 changed files with 23 additions and 4 deletions
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12
fs/io-wq.c
View File

@ -17,6 +17,7 @@
#include <linux/kthread.h>
#include <linux/rculist_nulls.h>
#include <linux/fs_struct.h>
#include <linux/task_work.h>
#include "io-wq.h"
@ -716,6 +717,9 @@ static int io_wq_manager(void *data)
complete(&wq->done);
while (!kthread_should_stop()) {
if (current->task_works)
task_work_run();
for_each_node(node) {
struct io_wqe *wqe = wq->wqes[node];
bool fork_worker[2] = { false, false };
@ -738,6 +742,9 @@ static int io_wq_manager(void *data)
schedule_timeout(HZ);
}
if (current->task_works)
task_work_run();
return 0;
err:
set_bit(IO_WQ_BIT_ERROR, &wq->state);
@ -1124,3 +1131,8 @@ void io_wq_destroy(struct io_wq *wq)
if (refcount_dec_and_test(&wq->use_refs))
__io_wq_destroy(wq);
}
struct task_struct *io_wq_get_task(struct io_wq *wq)
{
return wq->manager;
}

2
fs/io-wq.h
View File

@ -136,6 +136,8 @@ typedef bool (work_cancel_fn)(struct io_wq_work *, void *);
enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
void *data);
struct task_struct *io_wq_get_task(struct io_wq *wq);
#if defined(CONFIG_IO_WQ)
extern void io_wq_worker_sleeping(struct task_struct *);
extern void io_wq_worker_running(struct task_struct *);

13
fs/io_uring.c
View File

@ -4120,6 +4120,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
__poll_t mask, task_work_func_t func)
{
struct task_struct *tsk;
int ret;
/* for instances that support it check for an event match first: */
if (mask && !(mask & poll->events))
@ -4133,11 +4134,15 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
req->result = mask;
init_task_work(&req->task_work, func);
/*
* If this fails, then the task is exiting. If that is the case, then
* the exit check will ultimately cancel these work items. Hence we
* don't need to check here and handle it specifically.
* If this fails, then the task is exiting. Punt to one of the io-wq
* threads to ensure the work gets run, we can't always rely on exit
* cancelation taking care of this.
*/
task_work_add(tsk, &req->task_work, true);
ret = task_work_add(tsk, &req->task_work, true);
if (unlikely(ret)) {
tsk = io_wq_get_task(req->ctx->io_wq);
task_work_add(tsk, &req->task_work, true);
}
wake_up_process(tsk);
return 1;
}