Date: Mon, 28 Dec 2009 15:18:17 +0800 From: David Xu <davidxu@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Daniel Eischen <deischen@freebsd.org>, freebsd-threads@freebsd.org Subject: Re: first patch for process-shared semaphore Message-ID: <4B385BB9.3010109@freebsd.org> In-Reply-To: <200912240759.47703.jhb@freebsd.org> References: <4B317741.8080004@freebsd.org> <4B32CADA.4010407@freebsd.org> <20091223221219.4416cef6@kan.dnsalias.net> <200912240759.47703.jhb@freebsd.org>
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John Baldwin wrote: > On Wednesday 23 December 2009 10:12:19 pm Alexander Kabaev wrote: >> On Thu, 24 Dec 2009 09:58:50 +0800 >> David Xu <davidxu@freebsd.org> wrote: >> >>> Alexander Kabaev wrote: >>>> On Thu, 24 Dec 2009 09:22:34 +0800 >>>> David Xu <davidxu@freebsd.org> wrote: >>>>> libthr does not require semaphore, it implements semaphore, >>>>> it is easier than other ways to implement the process-shared. >>>>> >>>> Let me rephrase: I do not think semaphores belong in libthr. They >>>> should be either in libc or in librt. >>>> >>>> >>> OK, does others really implement semaphore in librt ? >>> unfortunately, the librt already requires libpthread to implement >>> SIGEV_THREAD. >> I retract that. It appears that there is no consistency - Solaris put >> these into libc, Linux into libpthread ans SUSv2 hints that these >> belong with realtime functions. libthr is fine. > > I vote for libc. Single-threaded processes can use sem_open() and PSHARED > sem_init() as well. Single-threaded processes can even use non-PSHARED > sem_init() by using fork() to create new "threads" that share the semaphore. > May I can move all semaphore functions into libc and remove all semaphore related symbols from libthr ? In pratical, this is not a problem, because libthr itself is not dlopen-safe, all missing semaphore functions in libthr will be found in libc by rtld.
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