Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
io_uring/io-wq: don't trigger hung task for syzbot craziness
Use the same trick that blk_io_schedule() does to avoid triggering the
hung task warning (and potential reboot/panic, depending on system
settings), and only wait for half the hung task timeout at the time.
If we exceed the default IO_URING_EXIT_WAIT_MAX period where we expect
things to certainly have finished unless there's a bug, then throw a
WARN_ON_ONCE() for that case.
Reported-by: syzbot+4eb282331cab6d5b6588@syzkaller.appspotmail.com
Tested-by: syzbot+4eb282331cab6d5b6588@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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io_uring/io-wq.c
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io_uring/io-wq.c
···
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#include <linux/task_work.h>
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#include <linux/audit.h>
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#include <linux/mmu_context.h>
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#include <linux/sched/sysctl.h>
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#include <uapi/linux/io_uring.h>
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#include "io-wq.h"
···
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static void io_wq_exit_workers(struct io_wq *wq)
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{
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unsigned long timeout, warn_timeout;
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if (!wq->task)
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return;
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···
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io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);
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rcu_read_unlock();
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io_worker_ref_put(wq);
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wait_for_completion(&wq->worker_done);
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/*
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* Shut up hung task complaint, see for example
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*
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* https://lore.kernel.org/all/696fc9e7.a70a0220.111c58.0006.GAE@google.com/
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*
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* where completely overloading the system with tons of long running
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* io-wq items can easily trigger the hung task timeout. Only sleep
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* uninterruptibly for half that time, and warn if we exceeded end
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* up waiting more than IO_URING_EXIT_WAIT_MAX.
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*/
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timeout = sysctl_hung_task_timeout_secs * HZ / 2;
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warn_timeout = jiffies + IO_URING_EXIT_WAIT_MAX;
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do {
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if (wait_for_completion_timeout(&wq->worker_done, timeout))
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break;
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WARN_ON_ONCE(time_after(jiffies, warn_timeout));
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} while (1);
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spin_lock_irq(&wq->hash->wait.lock);
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list_del_init(&wq->wait.entry);