Commit c93493b7 authored by Linus Torvalds's avatar Linus Torvalds

Merge tag 'io_uring-5.8-2020-07-01' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "One fix in here, for a regression in 5.7 where a task is waiting in
  the kernel for a condition, but that condition won't become true until
  task_work is run. And the task_work can't be run exactly because the
  task is waiting in the kernel, so we'll never make any progress.

  One example of that is registering an eventfd and queueing io_uring
  work, and then the task goes and waits in eventfd read with the
  expectation that it'll get woken (and read an event) when the io_uring
  request completes. The io_uring request is finished through task_work,
  which won't get run while the task is looping in eventfd read"

* tag 'io_uring-5.8-2020-07-01' of git://git.kernel.dk/linux-block:
  io_uring: use signal based task_work running
  task_work: teach task_work_add() to do signal_wake_up()
parents cd77006e ce593a6c
......@@ -4072,6 +4072,21 @@ struct io_poll_table {
int error;
};
static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb,
int notify)
{
struct task_struct *tsk = req->task;
int ret;
if (req->ctx->flags & IORING_SETUP_SQPOLL)
notify = 0;
ret = task_work_add(tsk, cb, notify);
if (!ret)
wake_up_process(tsk);
return ret;
}
static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
__poll_t mask, task_work_func_t func)
{
......@@ -4095,13 +4110,13 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
* of executing it. We can't safely execute it anyway, as we may not
* have the needed state needed for it anyway.
*/
ret = task_work_add(tsk, &req->task_work, true);
ret = io_req_task_work_add(req, &req->task_work, TWA_SIGNAL);
if (unlikely(ret)) {
WRITE_ONCE(poll->canceled, true);
tsk = io_wq_get_task(req->ctx->io_wq);
task_work_add(tsk, &req->task_work, true);
}
task_work_add(tsk, &req->task_work, 0);
wake_up_process(tsk);
}
return 1;
}
......@@ -6182,19 +6197,20 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
do {
prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
TASK_INTERRUPTIBLE);
/* make sure we run task_work before checking for signals */
if (current->task_works)
task_work_run();
if (io_should_wake(&iowq, false))
break;
schedule();
if (signal_pending(current)) {
ret = -EINTR;
ret = -ERESTARTSYS;
break;
}
if (io_should_wake(&iowq, false))
break;
schedule();
} while (1);
finish_wait(&ctx->wait, &iowq.wq);
restore_saved_sigmask_unless(ret == -EINTR);
restore_saved_sigmask_unless(ret == -ERESTARTSYS);
return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
}
......
......@@ -19,6 +19,7 @@ struct task_struct;
#define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */
#define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */
#define JOBCTL_TRAP_FREEZE_BIT 23 /* trap for cgroup freezer */
#define JOBCTL_TASK_WORK_BIT 24 /* set by TWA_SIGNAL */
#define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT)
#define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT)
......@@ -28,9 +29,10 @@ struct task_struct;
#define JOBCTL_TRAPPING (1UL << JOBCTL_TRAPPING_BIT)
#define JOBCTL_LISTENING (1UL << JOBCTL_LISTENING_BIT)
#define JOBCTL_TRAP_FREEZE (1UL << JOBCTL_TRAP_FREEZE_BIT)
#define JOBCTL_TASK_WORK (1UL << JOBCTL_TASK_WORK_BIT)
#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK | JOBCTL_TASK_WORK)
extern bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask);
extern void task_clear_jobctl_trapping(struct task_struct *task);
......
......@@ -13,7 +13,10 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
twork->func = func;
}
int task_work_add(struct task_struct *task, struct callback_head *twork, bool);
#define TWA_RESUME 1
#define TWA_SIGNAL 2
int task_work_add(struct task_struct *task, struct callback_head *twork, int);
struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
void task_work_run(void);
......
......@@ -2529,9 +2529,6 @@ bool get_signal(struct ksignal *ksig)
struct signal_struct *signal = current->signal;
int signr;
if (unlikely(current->task_works))
task_work_run();
if (unlikely(uprobe_deny_signal()))
return false;
......@@ -2544,6 +2541,13 @@ bool get_signal(struct ksignal *ksig)
relock:
spin_lock_irq(&sighand->siglock);
current->jobctl &= ~JOBCTL_TASK_WORK;
if (unlikely(current->task_works)) {
spin_unlock_irq(&sighand->siglock);
task_work_run();
goto relock;
}
/*
* Every stopped thread goes here after wakeup. Check to see if
* we should notify the parent, prepare_signal(SIGCONT) encodes
......
......@@ -25,9 +25,10 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
* 0 if succeeds or -ESRCH.
*/
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
task_work_add(struct task_struct *task, struct callback_head *work, int notify)
{
struct callback_head *head;
unsigned long flags;
do {
head = READ_ONCE(task->task_works);
......@@ -36,8 +37,19 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
work->next = head;
} while (cmpxchg(&task->task_works, head, work) != head);
if (notify)
switch (notify) {
case TWA_RESUME:
set_notify_resume(task);
break;
case TWA_SIGNAL:
if (lock_task_sighand(task, &flags)) {
task->jobctl |= JOBCTL_TASK_WORK;
signal_wake_up(task, 0);
unlock_task_sighand(task, &flags);
}
break;
}
return 0;
}
......
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