Date: Sat, 21 Nov 1998 03:35:51 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: DBECK@ludens.elte.hu (David Beck) Cc: tlambert@primenet.com, freebsd-hackers@FreeBSD.ORG Subject: Re: SYSV Semaphores & mmap problems Message-ID: <199811210335.UAA09506@usr08.primenet.com> In-Reply-To: <Pine.VMS.3.91-vms-b4.981120095517.8865A-100000@ludens.elte.hu> from "David Beck" at Nov 20, 98 10:00:31 am
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> > > I ran into two problems with FreeBSD: > > > 1., If I create a program with a few threads and then I block > > > one thread with a SYSV semaphore, then it blocks all threads. > > > Any ideas ? > > > > Use a mutex instead. SYSV semaphores are not process reentrant > > (they're semaphores). Neither are pthreads mutexes, but at > > least you will only block threads wanting the mutex instead of > > all threads. > > Yep. The problem is to control access to a shared memory segment > between unrelated processes and in the same time the server process > actually is a multithreaded process. Use fcntl(2) based locks. Preferrably against an mmap'ed file as the shared memory region instead of a SYSV shared memory region, to avoid using up kernel virtual address space. Alternately, someone need to write a non-blocking version of the system call and implement call conversion in a (new) libipc_r. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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