lkml.org 
[lkml]   [2009]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: broken do_each_pid_{thread,task}
On 02/24, Jiri Slaby wrote:
>
> On 15.12.2008 18:09, Oleg Nesterov wrote:
>> On 12/15, Oleg Nesterov wrote:
>>> On 12/14, Eric W. Biederman wrote:
>>>> Although seeing the unexpected corner case it gets us into I think it would
>>>> be good to reconsider this test.
>>
>> So. I can't decide whether this patch is cleanup or the further
>> uglification, but if anyone likes it I will be happy to send it.
>
> FWIW I don't like the patch :)

Well, I agree, it is not very nice ;)

But why do you dislike it? Yes, the implementation of pid_for_each_task()
is not simple. Partly because hlist_for_each_entry_rcu() is ugly and
imho should be fixed (see btw http://marc.info/?t=120879441200004).

But with this patch the callers become simpler, we can just do

pid_for_each_task(pid, type, task)
do_something(task);

instead of

do_each_pid_task(pid, type, task) {
do_something(task);
} while_each_pid_task(pid, type, task);

and we can use break/continue safely.

> Otherwise I'll add at least a big warning about using break/cont
> statements inside the loop.

Agreed, this would be nice.

>> +#define pid_for_each_task(pid, type, p) \
>> + for (p = (pid) ? (void*)(pid)->tasks[type].first : NULL; \
>> + rcu_dereference(p)&& ({ \
>> + prefetch(((struct hlist_node*)p)->next); \
>> + p = hlist_entry((void*)p, typeof(*p), pids[type].node); \
>> + 1; }); \
>> + p = ((type) != PIDTYPE_PID) ? \
>> + (void*)(p)->pids[type].node.next : NULL)
>> +

Really, is this too bad?

Oleg.



\
 
 \ /
  Last update: 2009-02-24 16:55    [W:0.089 / U:0.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site