[PATCH 0/1] Fix ftrace oops/hang on RISC-V and ARM64
Colin Ian King
colin.king at canonical.com
Wed Oct 28 10:52:24 UTC 2020
Forgot to add [SRU][GROOVY] to $SUBJECT
On 28/10/2020 10:48, 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.
> The only change is the the functions are no longer traceable via
> ftrace, which is the desired operation.
> Zong Li (1):
> stop_machine, rcu: Mark functions as notrace
> kernel/rcu/tree.c | 2 +-
> kernel/stop_machine.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
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