Messages in this thread | | | Date | Thu, 5 Oct 2017 18:19:30 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] drm/i915: Preallocate mmu notifier to unbreak cpu hotplug deadlock |
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On Thu, 5 Oct 2017, Daniel Vetter wrote: > On Thu, Oct 05, 2017 at 05:23:20PM +0200, Thomas Gleixner wrote: > > Aside of that, is it really required to use stomp_machine() for this > > synchronization? We certainly have less intrusive mechansisms than that. > > Yeah, the stop_machine needs to go, I'm working on something that uses > rcu_read_lock+synchronize_rcu for this case. Probably shouldn't have > merged even. > > Now this one isn't the one I wanted to fix with this patch since there's > clearly something dubious going on on the i915 side too.
I already wondered :)
> The proper trace, with the same part on the cpu hotplug side, highlights > that you can't allocate a workqueue while hodling mmap_sem. That one > matches patch description&diff a bit better :-)
> Sorry for misleading you, should have checked to attach the right one. No > stop_machine()/i915_gem_set_wedged() in the below one.
Well the problem is more or less the same and what I said about solving it in a different place is still valid. I think about it some more, but don't expect wonders :)
Thanks,
tglx
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