1. 24 Feb, 2012 1 commit
    • Oleg Nesterov's avatar
      epoll: introduce POLLFREE to flush ->signalfd_wqh before kfree() · d80e731e
      Oleg Nesterov authored
      This patch is intentionally incomplete to simplify the review.
      It ignores ep_unregister_pollwait() which plays with the same wqh.
      See the next change.
      
      epoll assumes that the EPOLL_CTL_ADD'ed file controls everything
      f_op->poll() needs. In particular it assumes that the wait queue
      can't go away until eventpoll_release(). This is not true in case
      of signalfd, the task which does EPOLL_CTL_ADD uses its ->sighand
      which is not connected to the file.
      
      This patch adds the special event, POLLFREE, currently only for
      epoll. It expects that init_poll_funcptr()'ed hook should do the
      necessary cleanup. Perhaps it should be defined as EPOLLFREE in
      eventpoll.
      
      __cleanup_sighand() is changed to do wake_up_poll(POLLFREE) if
      ->signalfd_wqh is not empty, we add the new signalfd_cleanup()
      helper.
      
      ep_poll_callback(POLLFREE) simply does list_del_init(task_list).
      This make this poll entry inconsistent, but we don't care. If you
      share epoll fd which contains our sigfd with another process you
      should blame yourself. signalfd is "really special". I simply do
      not know how we can define the "right" semantics if it used with
      epoll.
      
      The main problem is, epoll calls signalfd_poll() once to establish
      the connection with the wait queue, after that signalfd_poll(NULL)
      returns the different/inconsistent results depending on who does
      EPOLL_CTL_MOD/signalfd_read/etc. IOW: apart from sigmask, signalfd
      has nothing to do with the file, it works with the current thread.
      
      In short: this patch is the hack which tries to fix the symptoms.
      It also assumes that nobody can take tasklist_lock under epoll
      locks, this seems to be true.
      
      Note:
      
      	- we do not have wake_up_all_poll() but wake_up_poll()
      	  is fine, poll/epoll doesn't use WQ_FLAG_EXCLUSIVE.
      
      	- signalfd_cleanup() uses POLLHUP along with POLLFREE,
      	  we need a couple of simple changes in eventpoll.c to
      	  make sure it can't be "lost".
      Reported-by: default avatarMaxime Bizon <mbizon@freebox.fr>
      Cc: <stable@kernel.org>
      Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      d80e731e
  2. 08 Oct, 2010 1 commit
  3. 30 Jan, 2009 1 commit
  4. 24 Jul, 2008 2 commits
    • Ulrich Drepper's avatar
      flag parameters: NONBLOCK in signalfd · 5fb5e049
      Ulrich Drepper authored
      This patch adds support for the SFD_NONBLOCK flag to signalfd4.  The
      additional changes needed are minimal.
      
      The following test must be adjusted for architectures other than x86 and
      x86-64 and in case the syscall numbers changed.
      
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      #include <fcntl.h>
      #include <signal.h>
      #include <stdio.h>
      #include <unistd.h>
      #include <sys/syscall.h>
      
      #ifndef __NR_signalfd4
      # ifdef __x86_64__
      #  define __NR_signalfd4 289
      # elif defined __i386__
      #  define __NR_signalfd4 327
      # else
      #  error "need __NR_signalfd4"
      # endif
      #endif
      
      #define SFD_NONBLOCK O_NONBLOCK
      
      int
      main (void)
      {
        sigset_t ss;
        sigemptyset (&ss);
        sigaddset (&ss, SIGUSR1);
        int fd = syscall (__NR_signalfd4, -1, &ss, 8, 0);
        if (fd == -1)
          {
            puts ("signalfd4(0) failed");
            return 1;
          }
        int fl = fcntl (fd, F_GETFL);
        if (fl == -1)
          {
            puts ("fcntl failed");
            return 1;
          }
        if (fl & O_NONBLOCK)
          {
            puts ("signalfd4(0) set non-blocking mode");
            return 1;
          }
        close (fd);
      
        fd = syscall (__NR_signalfd4, -1, &ss, 8, SFD_NONBLOCK);
        if (fd == -1)
          {
            puts ("signalfd4(SFD_NONBLOCK) failed");
            return 1;
          }
        fl = fcntl (fd, F_GETFL);
        if (fl == -1)
          {
            puts ("fcntl failed");
            return 1;
          }
        if ((fl & O_NONBLOCK) == 0)
          {
            puts ("signalfd4(SFD_NONBLOCK) does not set non-blocking mode");
            return 1;
          }
        close (fd);
      
        puts ("OK");
      
        return 0;
      }
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      Signed-off-by: default avatarUlrich Drepper <drepper@redhat.com>
      Acked-by: default avatarDavide Libenzi <davidel@xmailserver.org>
      Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      5fb5e049
    • Ulrich Drepper's avatar
      flag parameters: signalfd · 9deb27ba
      Ulrich Drepper authored
      This patch adds the new signalfd4 syscall.  It extends the old signalfd
      syscall by one parameter which is meant to hold a flag value.  In this
      patch the only flag support is SFD_CLOEXEC which causes the close-on-exec
      flag for the returned file descriptor to be set.
      
      A new name SFD_CLOEXEC is introduced which in this implementation must
      have the same value as O_CLOEXEC.
      
      The following test must be adjusted for architectures other than x86 and
      x86-64 and in case the syscall numbers changed.
      
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      #include <fcntl.h>
      #include <signal.h>
      #include <stdio.h>
      #include <unistd.h>
      #include <sys/syscall.h>
      
      #ifndef __NR_signalfd4
      # ifdef __x86_64__
      #  define __NR_signalfd4 289
      # elif defined __i386__
      #  define __NR_signalfd4 327
      # else
      #  error "need __NR_signalfd4"
      # endif
      #endif
      
      #define SFD_CLOEXEC O_CLOEXEC
      
      int
      main (void)
      {
        sigset_t ss;
        sigemptyset (&ss);
        sigaddset (&ss, SIGUSR1);
        int fd = syscall (__NR_signalfd4, -1, &ss, 8, 0);
        if (fd == -1)
          {
            puts ("signalfd4(0) failed");
            return 1;
          }
        int coe = fcntl (fd, F_GETFD);
        if (coe == -1)
          {
            puts ("fcntl failed");
            return 1;
          }
        if (coe & FD_CLOEXEC)
          {
            puts ("signalfd4(0) set close-on-exec flag");
            return 1;
          }
        close (fd);
      
        fd = syscall (__NR_signalfd4, -1, &ss, 8, SFD_CLOEXEC);
        if (fd == -1)
          {
            puts ("signalfd4(SFD_CLOEXEC) failed");
            return 1;
          }
        coe = fcntl (fd, F_GETFD);
        if (coe == -1)
          {
            puts ("fcntl failed");
            return 1;
          }
        if ((coe & FD_CLOEXEC) == 0)
          {
            puts ("signalfd4(SFD_CLOEXEC) does not set close-on-exec flag");
            return 1;
          }
        close (fd);
      
        puts ("OK");
      
        return 0;
      }
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      [akpm@linux-foundation.org: add sys_ni stub]
      Signed-off-by: default avatarUlrich Drepper <drepper@redhat.com>
      Acked-by: default avatarDavide Libenzi <davidel@xmailserver.org>
      Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
      Cc: <linux-arch@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      9deb27ba
  5. 03 Feb, 2008 1 commit
  6. 17 Oct, 2007 1 commit
  7. 20 Sep, 2007 1 commit
    • Davide Libenzi's avatar
      signalfd simplification · b8fceee1
      Davide Libenzi authored
      This simplifies signalfd code, by avoiding it to remain attached to the
      sighand during its lifetime.
      
      In this way, the signalfd remain attached to the sighand only during
      poll(2) (and select and epoll) and read(2).  This also allows to remove
      all the custom "tsk == current" checks in kernel/signal.c, since
      dequeue_signal() will only be called by "current".
      
      I think this is also what Ben was suggesting time ago.
      
      The external effect of this, is that a thread can extract only its own
      private signals and the group ones.  I think this is an acceptable
      behaviour, in that those are the signals the thread would be able to
      fetch w/out signalfd.
      Signed-off-by: default avatarDavide Libenzi <davidel@xmailserver.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b8fceee1
  8. 11 May, 2007 1 commit
    • Davide Libenzi's avatar
      signal/timer/event: signalfd core · fba2afaa
      Davide Libenzi authored
      This patch series implements the new signalfd() system call.
      
      I took part of the original Linus code (and you know how badly it can be
      broken :), and I added even more breakage ;) Signals are fetched from the same
      signal queue used by the process, so signalfd will compete with standard
      kernel delivery in dequeue_signal().  If you want to reliably fetch signals on
      the signalfd file, you need to block them with sigprocmask(SIG_BLOCK).  This
      seems to be working fine on my Dual Opteron machine.  I made a quick test
      program for it:
      
      http://www.xmailserver.org/signafd-test.c
      
      The signalfd() system call implements signal delivery into a file descriptor
      receiver.  The signalfd file descriptor if created with the following API:
      
      int signalfd(int ufd, const sigset_t *mask, size_t masksize);
      
      The "ufd" parameter allows to change an existing signalfd sigmask, w/out going
      to close/create cycle (Linus idea).  Use "ufd" == -1 if you want a brand new
      signalfd file.
      
      The "mask" allows to specify the signal mask of signals that we are interested
      in.  The "masksize" parameter is the size of "mask".
      
      The signalfd fd supports the poll(2) and read(2) system calls.  The poll(2)
      will return POLLIN when signals are available to be dequeued.  As a direct
      consequence of supporting the Linux poll subsystem, the signalfd fd can use
      used together with epoll(2) too.
      
      The read(2) system call will return a "struct signalfd_siginfo" structure in
      the userspace supplied buffer.  The return value is the number of bytes copied
      in the supplied buffer, or -1 in case of error.  The read(2) call can also
      return 0, in case the sighand structure to which the signalfd was attached,
      has been orphaned.  The O_NONBLOCK flag is also supported, and read(2) will
      return -EAGAIN in case no signal is available.
      
      If the size of the buffer passed to read(2) is lower than sizeof(struct
      signalfd_siginfo), -EINVAL is returned.  A read from the signalfd can also
      return -ERESTARTSYS in case a signal hits the process.  The format of the
      struct signalfd_siginfo is, and the valid fields depends of the (->code &
      __SI_MASK) value, in the same way a struct siginfo would:
      
      struct signalfd_siginfo {
      	__u32 signo;	/* si_signo */
      	__s32 err;	/* si_errno */
      	__s32 code;	/* si_code */
      	__u32 pid;	/* si_pid */
      	__u32 uid;	/* si_uid */
      	__s32 fd;	/* si_fd */
      	__u32 tid;	/* si_fd */
      	__u32 band;	/* si_band */
      	__u32 overrun;	/* si_overrun */
      	__u32 trapno;	/* si_trapno */
      	__s32 status;	/* si_status */
      	__s32 svint;	/* si_int */
      	__u64 svptr;	/* si_ptr */
      	__u64 utime;	/* si_utime */
      	__u64 stime;	/* si_stime */
      	__u64 addr;	/* si_addr */
      };
      
      [akpm@linux-foundation.org: fix signalfd_copyinfo() on i386]
      Signed-off-by: default avatarDavide Libenzi <davidel@xmailserver.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      fba2afaa