I built a Trusty test kernel with a cherry-pick of dfbafc99. This test kernel can be downloaded from:
http://kernel.ubuntu.com/~jsalisbury/lp1486146/ Can you test this kernel and see if it resolves this bug? Thanks in advance! ** Also affects: linux (Ubuntu Precise) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Vivid) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Wily) Importance: High Status: Triaged ** Also affects: linux (Ubuntu Trusty) Importance: Undecided Status: New ** Changed in: linux (Ubuntu Vivid) Status: New => Triaged ** Changed in: linux (Ubuntu Trusty) Status: New => Triaged ** No longer affects: linux (Ubuntu Precise) ** Changed in: linux (Ubuntu Trusty) Importance: Undecided => High ** Changed in: linux (Ubuntu Vivid) Importance: Undecided => High -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1486146 Title: recvfrom SYSCALL infinite loop/deadlock chewing 100% CPU (MSG_PEEK|MSG_WAITALL) Status in Linux: Unknown Status in linux package in Ubuntu: Triaged Status in linux source package in Trusty: Triaged Status in linux source package in Vivid: Triaged Status in linux source package in Wily: Triaged Bug description: In a multi-threaded pthreads process running on Ubuntu 14.04 AMD64 (with over 1000 threads) which uses real time FIFO scheduling, we occasionally see calls to recv() with flags (MSG_PEEK | MSG_WAITALL) get stuck in an infinte loop or deadlock meaning the threads lock up chewing as much CPU as they can (due to FIFO scheduling) while stuck inside recv(). Here's an example gdb back trace: [Switching to thread 4 (Thread 0x7f6040546700 (LWP 27251))] #0 0x00007f6231d2f7eb in __libc_recv (fd=fd@entry=146, buf=buf@entry=0x7f6040543600, n=n@entry=5, flags=-1, flags@entry=258) at ../sysdeps/unix/sysv/linux/x86_64/recv.c:33 33 ../sysdeps/unix/sysv/linux/x86_64/recv.c: No such file or directory. (gdb) bt #0 0x00007f6231d2f7eb in __libc_recv (fd=fd@entry=146, buf=buf@entry=0x7f6040543600, n=n@entry=5, flags=-1, flags@entry=258) at ../sysdeps/unix/sysv/linux/x86_64/recv.c:33 #1 0x0000000000421945 in recv (__flags=258, __n=5, __buf=0x7f6040543600, __fd=146) at /usr/include/x86_64-linux-gnu/bits/socket2.h:44 [snip] The socket is a TCP socket in blocking mode, the recv() call is inside an outer loop with a counter, and I've checked the counter with gdb and it's always at 1, meaning that I'm sure that the outer loop isn't the problem, the thread is indeed deadlocked inside the recv() internals. Other nodes: * There always seems to be 2 or more threads deadlocked in the same place (same recv() call but with distinct FDs) * The threads calling recv() have cancellation disbaled by previously executing: thread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL); I've even tried adding a poll() call for POLLRDNORM on the socket before calling recv() with MSG_PEEK | MSG_WAITALL flags to try to make sure there's data available on the socket before calling *recv()*, but it makes no difference. So, I don't know what is wrong here, I've read all the recv() documentation and believe that recv() is being used correctly, the only conclusion I can come to is that there is a bug in libc recv() when using flags MSG_PEEK | MSG_WAITALL with thousands of pthreads running. To manage notifications about this bug go to: https://bugs.launchpad.net/linux/+bug/1486146/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp