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SubjectRe: [PATCH 1/3] comm: Introduce comm_lock spinlock to protect task->comm access

* John Stultz <john.stultz@linaro.org> wrote:

> The implicit rules for current->comm access being safe without locking are no
> longer true. Accessing current->comm without holding the task lock may result
> in null or incomplete strings (however, access won't run off the end of the
> string).

This is rather unfortunate - task->comm is used in a number of performance
critical codepaths such as tracing.

Why does this matter so much? A NULL string is not a big deal.

Note, since task->comm is 16 bytes there's the CMPXCHG16B instruction on x86
which could be used to update it atomically, should atomicity really be
desired.

Thanks,

Ingo


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