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

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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()
This commit is contained in:
Linus Torvalds
2020-07-02 14:56:22 -07:00
parent cd77006e01 ce593a6c48
commit c93493b7cd
5 changed files with 52 additions and 15 deletions
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10
kernel/signal.c
View File

@@ -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

16
kernel/task_work.c
View File

@@ -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;
}