From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Dake Subject: Re: [PATCH] change thread-unsafe readdir to thread-safe readdir_r calls Date: Wed, 07 Jul 2010 15:17:12 -0700 Message-ID: <4C34FCE8.4070208@redhat.com> References: <1278527821-14804-1-git-send-email-sdake@redhat.com> <20100707185257.GJ4630@obsidianresearch.com> <4C34D208.1000705@redhat.com> <20100707204712.GK4630@obsidianresearch.com> <4C34F09D.6080908@redhat.com> <20100707214920.GN4630@obsidianresearch.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100707214920.GN4630-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jason Gunthorpe Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 07/07/2010 02:49 PM, Jason Gunthorpe wrote: > On Wed, Jul 07, 2010 at 02:24:45PM -0700, Steven Dake wrote: > >> Not sure how to map a readdir to readdir_r on a thread unsafe system... >> perhaps with thread keys. In any regard, seems pointless, readdir_r is >> there and what POSIX specifies for this purpose. > > Override opendir and allocate the buffer then and return a pointer to it > through a custom 'DIR *'. > >>> FWIW, I've always considered readdir_r to be broken, you pass in a >>> buffer without passing in a size and hope everything works out. Your >> >> I also have objections to some POSIX standard APIs - however, using >> non-reentrant POSIX apis when reentrant POSIX APIs are available seems >> counterproductive. > > Well, if the non-reentrant ones are badly designed I'm not sure it is > a good trade.. Ie Solaris's man pages say: > > It is safe to use readdir() in a threaded application, so long as only > one thread reads from the directory stream at any given time. The > readdir() function is generally preferred over the readdir_r() > function. > > Also see > > http://lists.grok.org.uk/pipermail/full-disclosure/2005-November/038295.html > > The horribleness of readdir_r is well documented, and is partly why > libc's advocate thread safe readdir() desipte the existence of > readdir_r. > >>> proposed patch to libibverbs is also not-portable because it uses >>> NAME_MAX, not pathconf.. Sigh POSIX. > >> On bsd/solaris/darwin/linux, NAME_MAX is defined. Not sure which other >> POSIX systems one would care about.. > > If all you care able is bsd/solaris/darwin/linux then this is a > non-problem, AFAIK they have sane libc's :) Ie I just checked and > openbsd libc has been using a dynamic buffer allocated at opendir > since 1996. > > If you care about theortical portability then you have to worry about > NAME_MAX too.. > Thanks I'll look into NAME_MAX for my server. Regards -steve > Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html