[petsc-dev] Signal handling

[Junchao Zhang]

On Mon, Mar 9, 2020 at 1:44 PM Lisandro Dalcin <dalcinl at gmail.com> wrote:

>
>
> On Mon, 9 Mar 2020 at 19:22, Junchao Zhang <jczhang at mcs.anl.gov> wrote:
>
>> Hi, Lisandro,
>>  It is very cool to see you can make petsc dance with slurm.
>>
>
> Oh, boy... another poor soul lost in Dante's inferno...
>
>
>> From you pseudo example, my comments are:
>>
>
> First of all, this is work in progress. I already have a few changes.
>
>
>> * Do we need a type PetscSigSet instead of explicit  int?
>>
>>
> Maybe, not a big deal.
>
>
>> * Why do PetscSignalBegin/End() have different argument types? Many petsc
>> XxxBegin/End() routines have the same arguments. It is easier to remember
>> for users.
>>
>>
> Right now I've change things this way:
>
> PETSC_EXTERN PetscErrorCode PetscSignalBegin(int);
> PETSC_EXTERN PetscErrorCode PetscSignalEnd(void);
>
> In my current implementation, I have no use for passing a signal set
> to PetscSignalEnd().
>

> Maybe we should rename to PetscSignalPush(sigset) / PetscSignalPop() ?
>
You can have PetscSignalEnd(int) without using the argument. Users are used
to styles of PETSc's XxxBegin/End(), XxxGet/XxxRestore().


>
>
>> * Why do you need PetscSigMask in public header?
>>
>>
> To construct a signal set to pass to Begin():
>
>   mask  = 0;
>   mask |= PetscSigMask(PETSC_SIGHUP);
>   mask |= PetscSigMask(PETSC_SIGINT);
>   mask |= PetscSigMask(PETSC_SIGCONT);
>   mask |= PetscSigMask(PETSC_SIGTERM);
>   mask |= PetscSigMask(PETSC_SIGUSR1);
>   mask |= PetscSigMask(PETSC_SIGUSR2);
>   ierr = PetscSignalBegin(mask);CHKERRQ(ierr);
>
> User can use your PetscSigSetAdd() to construct a SigSet and use it
in PetscSignalBegin or PetscSignalClear


>
>
>> Can user do PetscSignalClear(PETSC_SIGUSR1) instead of
>> PetscSignalClear(PetscSigMask(PETSC_SIGUSR1))?
>>
>>
> But then if you need to clear many signals, you have to call multiple
> times. Note that all my APIs PetscSignalXXX work with bitsets, not
> individual signals.
>
> Maybe we could have Remove(signum) and Clear(sigset) ?
>
> You can keep the "all PetscSignalXxx arguments are SigSet" design.  If
users pass a signal to them, you can detect this error, for example, by
using a 64-bit SigSet and leaving the lower 5 bits unused and starting the
first bitmask at 6-th bit.


>
>>  I like fewer and simpler public APIs.  Just my two cents.
>>
>>
> Much appreciated!. Let me think a bit more about it, I agree that the
> current API is a bit weird...
>
> PS: Do you  really think this may be actually useful in production to be
> worth to push into PETSc?
>
If you find it is useful, then I believe someone else will also.


>
>
> --
> Lisandro Dalcin
> ============
> Research Scientist
> Extreme Computing Research Center (ECRC)
> King Abdullah University of Science and Technology (KAUST)
> http://ecrc.kaust.edu.sa/
>
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