Messages in this thread | | | Subject | Re: [PATCH] x86,mm: print likely CPU at segfault time | From | Rik van Riel <> | Date | Fri, 23 Jul 2021 21:38:38 -0400 |
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On Wed, 2021-07-21 at 22:36 +0200, Thomas Gleixner wrote: > Rik, > > On Mon, Jul 19 2021 at 15:00, Rik van Riel wrote: > > > > Adding a printk to show_signal_msg() achieves that purpose. It > > isn't > > perfect since the task might get rescheduled on another CPU between > > when the fault hit and when the message is printed, but it should > > be > > good enough to show correlation between userspace and kernel errors > > when dealing with a bad CPU. > > we could collect the cpu number in do_*_addr_fault() before > interrupts > are enabled and just hand it through. There are only a few callchains > which end up in __bad_area_nosemaphore().
We could, but do we really want to add that to the hot path for page faults, when segfaults are so rare?
I suspect the simple patch I sent will be good enough to identify a bad CPU, even if only 3 out of 4 userspace crashes get attributed to the right CPU...
I would be happy to write a patch that does what you want though, so you can compare them side by side :)
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