Re: busyloop in sigchld_handler

[Andreas Schwab]

Sam Steingold <address@hidden> writes:

> Andreas Schwab wrote:
>> Sam Steingold <address@hidden> writes:
>>
>>> wait3 is a system call, which, when invoked in a loop, prevents the
>>> kernel from doing anything else (in this case, sending SIGCHLD to
>>> emacs). sleep allows the kernel some time to pass the signal.
>>
>> I don't find this explanation convincing at all.  Since the system call is
>> made _inside_ the signal handler, the signal is actually blocked here, so
>> it cannot be delivered anyway.
>
> yes, you are right.
> what I should have said was that by making a system call in a busyloop,
> emacs prevents the kernel from doing what it needs to do to the the child
> so that wait3 will succeed.

What does the kernel have to do?  The EINTR error will only happen when
the system call was interrupted _and_ a signal handler was called.

Andreas.

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Andreas Schwab, SuSE Labs, address@hidden
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