Messages in this thread | | | Subject | Re: [RESEND][RFC PATCH v2] waitfd | From | Scott James Remnant <> | Date | Sat, 10 Jan 2009 14:45:14 +0000 |
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On Wed, 2009-01-07 at 12:53 -0800, Roland McGrath wrote:
> New syscall should have gone to linux-api, I think. > > Do we really need another one for this? How about using signalfd plus > setting the child's exit_signal to a queuing (SIGRTMIN+n) signal instead of > SIGCHLD? It's slightly more magical for the userland process to know to do > that (fork -> clone SIGRTMIN). But compared to adding a syscall we don't > really have to add, maybe better. > This wouldn't help the init daemon case:
- the exit_signal is set on the child, not on the parent.
While the init daemon could clone() every new process and set exit_signal, this would not be set for processes reparented to init.
Even if we had a new syscall to change the exit_signal of a given process, *and* had the init reparent notification patch, this still wouldn't be sufficient; you'd have a race condition between the time you were notified of the reparent, and the time you set exit_signal, in which the child could die.
Since exit_signal is always reset to SIGCHLD before reparenting, this could be done by resetting it to a different signal; but at this point we're getting into a rather twisty method full of traps.
- exit_signal is reset to SIGCHLD on exec().
Pretty much a plan-killer ;)
Scott -- Scott James Remnant scott@canonical.com [unhandled content-type:application/pgp-signature] | |