Re: [PATCH 1/2] break out page allocation warning code

[David Rientjes <rientjes@google.com>]

On Wed, 27 Apr 2011, john stultz wrote:

> So thinking further, this can be simplified by adding the seqlock first,
> and then retaining the task_locking only in the set_task_comm path until
> all comm accessors are converted to using get_task_comm.
> 

On second thought, I think it would be better to just retain using a 
spinlock but instead of using alloc_lock, introduce a new spinlock to 
task_struct for the sole purpose of protecting comm.

And, instead, of using get_task_comm() to write into a preallocated 
buffer, I think it would be easier in the vast majority of cases that 
you'll need to convert to just provide task_comm_lock(p) and 
task_comm_unlock(p) so that p->comm can be dereferenced safely.  
get_task_comm() could use that interface itself and then write into a 
preallocated buffer.

The problem with using get_task_comm() everywhere is it requires 16 
additional bytes to be allocated on the stack in hundreds of locations 
around the kernel which may or may not be safe.

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