Messages in this thread | | | Date | Thu, 15 Feb 2024 18:26:59 -0500 | From | Kent Overstreet <> | Subject | Re: [PATCH] kernel/hung_task.c: export sysctl_hung_task_timeout_secs |
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On Thu, Feb 15, 2024 at 10:55:09AM -0800, Andrew Morton wrote: > On Wed, 14 Feb 2024 21:26:34 -0800 Christoph Hellwig <hch@infradead.org> wrote: > > > On Fri, Feb 09, 2024 at 02:09:35AM -0500, Kent Overstreet wrote: > > > needed for thread_with_file; also rare but not unheard of to need this > > > in module code, when blocking on user input. > > > > > > one workaround used by some code is wait_event_interruptible() - but > > > that can be buggy if the outer context isn't expecting unwinding. > > > > I don't think just exporting the variable ad thus allowing write > > access is a good idea. If we want to keep going down the route of > > this hack we should add an accessor function that returns the value. > > > > The cleaner solution would be a new task state that explicitly > > marks code than can sleep forever without triggerring the hang > > check. Although this might be a bit invaѕive and take a while.
I had the same thought.
> A new PF_whatever flag would solve that simply?
TASK_* flags are separate from PF_* flags, fortunately, and it doesn't look like anything but TASK_* flags go in task_struct->__state, so this shouldn't be a difficult change.
> Which are the potential use sites for such a thing?
There's a few places in the block layer that are using the sysctl value; those will be easy to fix. There's definitely more places abusing TASK_INTERRUPTIBLE, but aside from the ones in my code I can't think of a way to search for them.
But the block layer ones look a little suspect to me: the commit message indicates they were added becasue discards on some devices can take > 100 seconds - which is true, but this is a more general problem, there's other places we block on IO.
Might want to give this some more thought.
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