Re: [PATCH 1/3] comm: Introduce comm_lock spinlock to protecttask->comm access

[Ingo Molnar]

* John Stultz <john.stultz@xxxxxxxxxx> 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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