Messages in this thread | | | Subject | Re: [PATCH] modules: fix livelock in add_unformed_module() | From | Barret Rhoden <> | Date | Mon, 13 May 2019 10:37:03 -0400 |
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Hi -
On 5/13/19 7:23 AM, Prarit Bhargava wrote: [snip] > A module is loaded once for each cpu.
Does one CPU succeed in loading the module, and the others fail with EEXIST?
> My follow-up patch changes from wait_event_interruptible() to > wait_event_interruptible_timeout() so the CPUs are no longer sleeping and can > make progress on other tasks, which changes the return values from > wait_event_interruptible(). > > https://marc.info/?l=linux-kernel&m=155724085927589&w=2 > > I believe this also takes your concern into account?
That patch might work for me, but I think it papers over the bug where the check on old->state that you make before sleeping (was COMING || UNFORMED, now !LIVE) doesn't match the check to wake up in finished_loading().
The reason the issue might not show up in practice is that your patch basically polls, so the condition checks in finished_loading() are only a quicker exit.
If you squash my patch into yours, I think it will cover that case. Though if polling is the right answer here, it also raises the question of whether or not we even need finished_loading().
Barret
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