[ovs-dev] [threads 01/17] signals: Make thread-safe.

Ethan Jackson ethan at nicira.com
Wed Jun 5 21:06:17 UTC 2013


Acked-by: Ethan Jackson <ethan at nicira.com>

On Wed, Jun 5, 2013 at 1:05 PM, Ben Pfaff <blp at nicira.com> wrote:
> Signed-off-by: Ben Pfaff <blp at nicira.com>
> ---
>  lib/signals.c           |   66 ++++++++++-------------------------------------
>  lib/signals.h           |    4 ---
>  vswitchd/ovs-vswitchd.c |    1 -
>  3 files changed, 14 insertions(+), 57 deletions(-)
>
> diff --git a/lib/signals.c b/lib/signals.c
> index 99a36a4..1340f54 100644
> --- a/lib/signals.c
> +++ b/lib/signals.c
> @@ -40,80 +40,47 @@ VLOG_DEFINE_THIS_MODULE(signals);
>  #endif
>
>  struct signal {
> -    struct sigaction saved_sa;
> -    int signr;
> +    int fds[2];
>  };
>
> -static volatile sig_atomic_t signaled[N_SIGNALS];
> -
> -static int fds[2];
> +static struct signal signals[N_SIGNALS];
>
>  static void signal_handler(int signr);
>
> -/* Initializes the signals subsystem (if it is not already initialized).  Calls
> - * exit() if initialization fails.
> - *
> - * Calling this function is optional; it will be called automatically by
> - * signal_start() if necessary.  Calling it explicitly allows the client to
> - * prevent the process from exiting at an unexpected time. */
> -void
> -signal_init(void)
> -{
> -    static bool inited;
> -    if (!inited) {
> -        inited = true;
> -        xpipe_nonblocking(fds);
> -    }
> -}
> -
>  /* Sets up a handler for 'signr' and returns a structure that represents it.
>   *
> - * Only one handler for a given signal may be registered at a time. */
> + * Only one handler for a given signal may be registered. */
>  struct signal *
>  signal_register(int signr)
>  {
>      struct sigaction sa;
>      struct signal *s;
>
> -    signal_init();
> +    ovs_assert(signr >= 1 && signr < N_SIGNALS);
>
> -    s = xmalloc(sizeof *s);
> -    s->signr = signr;
> +    /* Create a pipe. */
> +    s = &signals[signr];
> +    ovs_assert(!s->fds[0] && !s->fds[1]);
> +    xpipe_nonblocking(s->fds);
>
> -    /* Set up signal handler. */
> -    ovs_assert(signr >= 1 && signr < N_SIGNALS);
> +    /* Install signal handler. */
>      memset(&sa, 0, sizeof sa);
>      sa.sa_handler = signal_handler;
>      sigemptyset(&sa.sa_mask);
>      sa.sa_flags = SA_RESTART;
> -    xsigaction(signr, &sa, &s->saved_sa);
> +    xsigaction(signr, &sa, NULL);
>
>      return s;
>  }
>
> -/* Unregisters the handler for 's', restores the signal handler that was in
> - * effect before signal_register() was called, and frees 's'. */
> -void
> -signal_unregister(struct signal *s)
> -{
> -    if (s) {
> -        xsigaction(s->signr, &s->saved_sa, NULL);
> -        free(s);
> -    }
> -}
> -
>  /* Returns true if signal 's' has been received since the last call to this
>   * function with argument 's'. */
>  bool
>  signal_poll(struct signal *s)
>  {
>      char buf[_POSIX_PIPE_BUF];
> -    ignore(read(fds[0], buf, sizeof buf));
> -    if (signaled[s->signr]) {
> -        signaled[s->signr] = 0;
> -        return true;
> -    }
> -    return false;
> +
> +    return read(s->fds[0], buf, sizeof buf) > 0;
>  }
>
>  /* Causes the next call to poll_block() to wake up when signal_poll(s) would
> @@ -121,19 +88,14 @@ signal_poll(struct signal *s)
>  void
>  signal_wait(struct signal *s)
>  {
> -    if (signaled[s->signr]) {
> -        poll_immediate_wake();
> -    } else {
> -        poll_fd_wait(fds[0], POLLIN);
> -    }
> +    poll_fd_wait(s->fds[0], POLLIN);
>  }
>
>  static void
>  signal_handler(int signr)
>  {
>      if (signr >= 1 && signr < N_SIGNALS) {
> -        ignore(write(fds[1], "", 1));
> -        signaled[signr] = true;
> +        ignore(write(signals[signr].fds[1], "", 1));
>      }
>  }
>
> diff --git a/lib/signals.h b/lib/signals.h
> index 015d329..b3983b2 100644
> --- a/lib/signals.h
> +++ b/lib/signals.h
> @@ -21,11 +21,7 @@
>  #include <stdbool.h>
>  #include "type-props.h"
>
> -void signal_init(void);
> -
>  struct signal *signal_register(int signr);
> -void signal_unregister(struct signal *);
> -
>  bool signal_poll(struct signal *);
>  void signal_wait(struct signal *);
>
> diff --git a/vswitchd/ovs-vswitchd.c b/vswitchd/ovs-vswitchd.c
> index 78ebd31..e11febd 100644
> --- a/vswitchd/ovs-vswitchd.c
> +++ b/vswitchd/ovs-vswitchd.c
> @@ -140,7 +140,6 @@ main(int argc, char *argv[])
>      }
>      bridge_exit();
>      unixctl_server_destroy(unixctl);
> -    signal_unregister(sighup);
>
>      return 0;
>  }
> --
> 1.7.2.5
>
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> http://openvswitch.org/mailman/listinfo/dev



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