Messages in this thread | | | Date | Fri, 25 Nov 2011 20:44:19 +0400 | From | Pavel Emelyanov <> | Subject | Re: [RFC][PATCH 0/3] fork: Add the ability to create tasks with given pids |
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On 11/25/2011 08:22 PM, Oleg Nesterov wrote: > On 11/25, Pavel Emelyanov wrote: >> >> The proposal is to implement the PR_RESERVE_PID prctl which allocates and puts a >> pid on the current. The subsequent fork() uses this pid, > > Oh. This is subjective, yes, but this doesn't clean to me. > > Amd why?? On the running system PR_RESERVE_PID can obviously fail anyway. > It only helps to avoid the race with another fork.
No. It can fail if you try to allocate a pid with given number. The API allows for pid generation. AFAIU this can help with Pedro's requirements to resurrect task with the same pid value it used to have before.
>> * one more field on struct pid is OK, since it size doesn't change (32 bit level is >> anyway not required, it's OK to reduce on down to 16 bits) > > Even if sizeof is the same, the new member and the code which plays > with ->flags doesn't make the things better ;) > >> * yes, we have +1 member on task_struct :( > > Yes, and this task_struct->rsv_pid acts as implicit parameter for the > next clone(). Doesn't look very nice to me. Plus the code complications.
Well, the last_pid is also an implicit parameter for the next clone() with sysctl approach :) But the code complication is the problem, yes :(
>> Oleg, Tejun, do you agree with such an approach? > > If set_last_pid doesn't work, I'd prefer CLONE_CHILD_USEPIDS.
OK, thanks.
> Oleg. > > . >
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