Messages in this thread | | | Date | Tue, 1 May 2001 18:02:22 +0200 | From | Pavel Machek <> | Subject | Re: Patch(?): bash-2.05/jobs.c loses interrupts |
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Hi!
> > Linux-2.4.4 has a change, for which I must accept blame, > > where fork() runs the child first, reducing unnecessary copy-on-write > > page duplications, because the child will usually promptly do an > > exec(). I understand this is pretty standard in most unixes. > > > > Peter Osterlund noticed an annoying side effect of this, > > which I think is a bash bug. He wrote: > > > > > Another thing is that the bash loop "while true ; do /bin/true ; done" is > > > not possible to interrupt with ctrl-c. > > > > I have reproduced this problem on a single CPU system. > > I also modified my kernel to sometimes run the fork child first > > and sometimes not. In that case, that loop would sometimes > > abort on a control-C and sometimes ignore it, but ignoring it > > would not make the loop less likely to abort on another control-C. > > I'm pretty sure the control-C was being delivered only to the child > > due to a race condition in bash, which may be mandated by posix. > > Did you reconfigure and rebuild bash on your machine running the 2.4 > kernel, or just use a bash binary built on a previous kernel > version?
This is nasty race condition. I do not believe you can test for it in configure.
This might happen on 2.4.3 (occasionally) too. Kernel is permitted to do any kind of scheduling!
Pavel
> Bash has an autoconf test that will, if it detects the need to do so, > force the job control code to synchronize between parent and child > when setting up the process group for a new pipeline. It may be the > case that you have to reconfigure and rebuild bash to enable that code. > > Look for PGRP_PIPE in config.h.
-- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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