site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com This isn't a race, see bottom of email! On 2010-01-18, at 3:16 PM, Godfrey van der Linden wrote:
G'day, all networking types.
I've recently tripped over a kernel race when attempting to connect with a DGRAM socket. This is the code fragment that is causing problems
struct sockaddr_un sa2; struct sockaddr_storage saLocal; socklen_t saLocalLen;
sa2.sun_family = AF_UNIX; strcpy(sa2.sun_path, kDefSocketName2); (void) unlink(kDefSocketName2);
sys_test(fd_skt = socket(AF_UNIX, SOCK_DGRAM, 0), "Can't open DGRAM socket %d", child_pid); sys_test(bind(fd_skt, (struct sockaddr *) &sa2, sizeof(sa2)), "Can't bind DGRAM socket %d", child_pid);
// Wait for first client message for connecting sys_test(recvfrom(fd_skt, msg, sizeof(msg), /* flags */ 0, (struct sockaddr *) &saLocal, &saLocalLen), "Error reading first message"); #if NOCRASH saP = (struct sockaddr_un *) &saLocal; #endif // NOCRASH sys_test(connect(fd_skt, (struct sockaddr *) &saLocal, saLocalLen), "Can't connect to client %d", child_pid);
notes: 1> sys_test is a macro that checks the result for -1 and crashes with the error if necessary. 2> sys_test is implemented within a do{ ... } while(0), i.e. the macros don't interact). 3> the server is single threaded and runs in its own process after a fork(). 4> The code is compiled with -O0 (no optimisation) 5> I'm running on an '06 intel iMac, which is dual core.
When I compile and run with -DNOCRASH=1 connect never seems to fail.
However if the connect directly follows the recvfrom then I get a "nwmark(main): Can't connect to client 53673 - Invalid argument(22)" about 50% of the time. Process is single threaded (see note <3>), so the saLocal variable is not being scribbled on between the recvfrom and the connect.
Has anybody seen the kernel race in this way before? Should I submit a bug?
It is not a race! I tried recvfrom()/usleep(100)/connect() it does not fix the problem! Is there any way that the sockaddr_storage returned from the recvfrom could be in an odd state. If I refer to it, even by just assigning the address this problem doesn't reproduce. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... This email sent to site_archiver@lists.apple.com