APPLIED U: Re: [PATCH 0/1] Fix ftrace oops/hang on RISC-V and ARM64
paolo.pisati at canonical.com
Fri Oct 30 11:45:49 UTC 2020
On Wed, Oct 28, 2020 at 10:48:24AM +0000, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> == SRU Groovy ==
> Running the ftrace self tests results in null pointer dereference oops
> on RISC-V and also on ARM64.
> == Fix ==
> Upstream commit https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=4230e2deaa484b385aa01d598b2aea8e7f2660a6
> == Testcase ==
> Run the kernel ftrace selftest. Without the fix ftrace oopses on RISC-V
> and ARM64 and can also hang on ARM64 too. With the fix, tests run
> without oopsing or hanging.
> == Regression Potential ==
> This fix marks two functions as notrace, so the functionality of the
> functions is not actually altered so the risk is negligible. If there
> was a change in behaviour then RCU and stop machine operations will
> break causing machine hangs. We don't observe this and RCU is used
> heavily in the kernel so the code appears to not change the RCU
> behaviour as expected.
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