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  1. 16 Jul, 2012 2 commits
    • Anders Kaseorg's avatar
      fifo: Do not restart open() if it already found a partner · 05d290d6
      Anders Kaseorg authored 
      If a parent and child process open the two ends of a fifo, and the
child immediately exits, the parent may receive a SIGCHLD before its
open() returns.  In that case, we need to make sure that open() will
return successfully after the SIGCHLD handler returns, instead of
throwing EINTR or being restarted.  Otherwise, the restarted open()
would incorrectly wait for a second partner on the other end.

The following test demonstrates the EINTR that was wrongly thrown from
the parent’s open().  Change .sa_flags = 0 to .sa_flags = SA_RESTART
to see a deadlock instead, in which the restarted open() waits for a
second reader that will never come.  (On my systems, this happens
pretty reliably within about 5 to 500 iterations.  Others report that
it manages to loop ~forever sometimes; YMMV.)

  #include <sys/stat.h>
  #include <sys/types.h>
  #include <sys/wait.h>
  #include <fcntl.h>
  #include <signal.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>

  #define CHECK(x) do if ((x) == -1) {perror(#x); abort();} while(0)

  void handler(int signum) {}

  int main()
  {
      struct sigaction act = {.sa_handler = handler, .sa_flags = 0};
      CHECK(sigaction(SIGCHLD, &act, NULL));
      CHECK(mknod("fifo", S_IFIFO | S_IRWXU, 0));
      for (;;) {
          int fd;
          pid_t pid;
          putc('.', stderr);
          CHECK(pid = fork());
          if (pid == 0) {
              CHECK(fd = open("fifo", O_RDONLY));
              _exit(0);
          }
          CHECK(fd = open("fifo", O_WRONLY));
          CHECK(close(fd));
          CHECK(waitpid(pid, NULL, 0));
      }
  }

This is what I suspect was causing the Git test suite to fail in
t9010-svn-fe.sh:

	http://bugs.debian.org/678852Signed-off-by: default avatarAnders Kaseorg <andersk@mit.edu>
Reviewed-by: default avatarJonathan Nieder <jrnieder@gmail.com>
Cc: stable@kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      05d290d6
    • Linus Torvalds's avatar
      Merge tag 'fixes-for-v3.5-rc6' of... · 1694a0a0
      Linus Torvalds authored 
      Merge tag 'fixes-for-v3.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl

Pull late pinctrl fixes from Linus Walleij:
- Two fixes to the i.MX driver

* tag 'fixes-for-v3.5-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
  pinctrl: pinctrl-imx6q: add missed mux function for USBOTG_ID
  pinctrl: pinctrl-imx: only print debug message when DEBUG is defined
      1694a0a0
  3. 14 Jul, 2012 13 commits
  5. 13 Jul, 2012 19 commits
  7. 12 Jul, 2012 5 commits
  9. 11 Jul, 2012 1 commit
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