Re: [SCM] systemtap: system-wide probe/trace tool branch, master, updated. release-1.6-594-g12aa5f9

[David Smith <dsmith at redhat dot com>]

On 12/14/2011 03:42 AM, Mark Wielaard wrote:

> On Tue, 2011-12-13 at 22:32 +0000, fche@sourceware.org wrote:

...

>>         entry = (struct __stp_tf_vma_entry *) _stp_kmalloc_gfp(size,
>> -                                                       STP_ALLOC_SLEEP_FLAGS);
>> +                                                               STP_ALLOC_FLAGS);
> 
> Urgh that hurts. Especially on memory constraint systems having to do
> non-sleeping allocations. Isn't there any way we can prevent this? Or at
> least detect that we are using a task_finder that doesn't notify us in
> user context? I think there are other places that assume the task_finder
> only notifies us about updates in user context, for example so we can
> check the build-id. Having a taks_finder that only operates in atomic
> contexts is pretty limiting.


We could postpone the pain a bit by changing the above to:

#ifdef CONFIG_UTRACE
         entry = (struct __stp_tf_vma_entry *) _stp_kmalloc_gfp(size,
		STP_ALLOC_SLEEP_FLAGS);
#else
         entry = (struct __stp_tf_vma_entry *) _stp_kmalloc_gfp(size,
		STP_ALLOC_FLAGS);
#endif

This way only systems using the new code use the non-sleepable alloc.

-- 
David Smith
dsmith@redhat.com
Red Hat
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