Re: [CRIU] [PATCH 3/3] signalfd: add ability to read siginfo-swithout dequeuing signals (v2)

From: Denys Vlasenko
Date: Mon Feb 11 2013 - 09:47:18 EST

On Mon, Feb 11, 2013 at 11:59 AM, Andrew Vagin <avagin@xxxxxxxxxxxxx> wrote:
>> > I suppose I had wondered along similar lines, but in a slightly
>> > different direction: would the use of a /proc interface to get the
>> > queued signals make some sense?
>> I think that /proc interface beats adding magic flags and magic semantic
>> to [p]read.
>> It also has the benefit of being human-readable. You don't need
>> to write a special C program to "cat /proc/$$/foo".
>> Andrey, I know that it is hard to let go of the code you invested time
>> and efforts in creating. But this isn't the last patch, is it?
>> You will need to retrieve yet more data for process checkpointing.
>> When you start working on the next patch for it, consider trying
>> /proc approach.
> I don't think that we need to convert siginfo into a human readable format
> in kernel.

My point is that bolting hacks onto various bits of kernel API
in order to support process checkpointing makes those APIs
(their in-kernel implementation) ridden with special cases
and harder to support in the future.

Process checkpointing needs to bite the bullet and
create its own API instead.

Whether it would be a /proc/PID/checkpoint or a
ptrace(PTRACE_GET_CHKPOINT_DATA) is another question.

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