Date: Sat, 11 Aug 2001 12:06:23 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Michael Robinson <robinson@netrinsics.com> Cc: current@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: _sigprocmask in malloc.c causes full file table? Message-ID: <3B75822F.E84799BD@mindspring.com> References: <200108110115.f7B1F4100321@netrinsics.com>
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Michael Robinson wrote: > > I'm currently trying to deal with the problem where malloc/free in a > signal handler will crash (in my case, the X window server) if a signal > arrives during malloc or free. The manual pages suck, since this should be under signal(3), not as a reference to sigaction(2), but... man 2 sigaction You can not allocate or free in signal handlers because malloc(3) and free(3) use brk(2) and sbrk(2), which are system calls that can't be used in a signal handler, since they are missing from the list of permitted function. Signals are pretty brain damaged anyway: the correct way to deal with them is to set a flag, and then handle them in the main event loop by checking the flag. NB: ANSI C requires you to mark this flag as "volatile", even though all externally referenced variables from signal handlers should be implicitly volatile, so that it doesn't optimize it into a register on you, and make your code not work. It's really not that hard to clean up the code... -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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