fd: Improve error handling of write_nonblock().

[paraslash.git] / signal.c

diff --git a/signal.c b/signal.c
index acc87802b33a841f8f5d7f90b971ae97a3edc3b0..0b7b47fa3d1401d57ae11ed107f487e9036a2870 100644 (file)
--- a/signal.c
+++ b/signal.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2004-2009 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2004-2012 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -7,7 +7,6 @@
 
 #include <signal.h>
 #include <sys/types.h>
-#include <dirent.h>
 
 #include "para.h"
 #include "error.h"
@@ -103,60 +102,112 @@ int para_reap_child(pid_t *pid)
 }
 
 /**
- * Paraslash's zombie killer.
+ * Install the given handler for the given signal.
  *
- * It just calls \p para_reap_child() until there are no more children left to
- * reap.
+ * \param sig The number of the signal to catch.
+ * \param handler to be installed, \p SIG_IGN, or \p SIG_DFL.
+ *
+ * This either succeeds or calls exit(EXIT_FAILURE).
+ *
+ * \sa sigaction(2).
  */
-void para_reap_children(void)
+void para_sigaction(int sig, void (*handler)(int))
 {
-       pid_t pid;
+       struct sigaction act;
 
-       while (para_reap_child(&pid) > 0)
-               ; /* nothing */
+       PARA_DEBUG_LOG("catching signal %d\n", sig);
+       act.sa_handler = handler;
+       sigemptyset(&act.sa_mask);
+       act.sa_flags = 0;
+       if (sig == SIGALRM) {
+               #ifdef SA_INTERRUPT /* SunOS */
+                       act.sa_flags |= SA_INTERRUPT;
+               #endif
+       } else {
+               #ifdef SA_RESTART /* BSD */
+                       act.sa_flags |= SA_RESTART;
+               #endif
+       }
+       if (sigaction(sig, &act, NULL) >= 0)
+               return;
+       PARA_EMERG_LOG("failed to install signal handler for signal %d\n",
+               sig);
+       exit(EXIT_FAILURE);
 }
 
 /**
- * Wrapper around signal(2).
+ * Install the generic signal handler for the given signal number.
  *
  * \param sig The number of the signal to catch.
  *
- * This installs the generic signal handler for the given signal.
+ * \sa signal(2), sigaction(2).
+ */
+void para_install_sighandler(int sig)
+{
+       para_sigaction(sig, &generic_signal_handler);
+}
+
+/**
+ * Block a signal for the caller.
+ *
+ * \param sig The signal to block.
  *
- * \return This function returns 1 on success and \p -E_SIGNAL_SIG_ERR on errors.
+ * This sets the given signal in the current signal mask of the calling process
+ * to prevent this signal from delivery.
  *
- * \sa signal(2).
+ * \sa \ref para_unblock_signal(), sigprocmask(2), sigaddset(3).
  */
-int para_install_sighandler(int sig)
+void para_block_signal(int sig)
 {
-       PARA_DEBUG_LOG("catching signal %d\n", sig);
-       return signal(sig, &generic_signal_handler) == SIG_ERR?  -E_SIGNAL_SIG_ERR : 1;
+       sigset_t set;
+
+       PARA_DEBUG_LOG("blocking signal %d\n", sig);
+       sigemptyset(&set);
+       sigaddset(&set, sig);
+       sigprocmask(SIG_BLOCK, &set, NULL);
 }
 
 /**
- * Return the number of next pending signal.
+ * Unblock a signal.
+ *
+ * \param sig The signal to unblock.
  *
- * This should be called if the fd for the signal pipe is ready for reading.
+ * This function removes the given signal from the current set of blocked
+ * signals.
  *
- * \return On success, the number of the received signal is returned.  If the
- * read returned zero or was interrupted by another signal the function returns
- * 0.  Otherwise, a negative error value is returned.
+ * \sa \ref para_block_signal(), sigprocmask(2), sigaddset(3).
  */
-int para_next_signal(void)
+void para_unblock_signal(int sig)
 {
-       int s;
-       ssize_t r = read(signal_pipe[0], &s, sizeof(s));
+       sigset_t set;
 
-       if (!r) {
-               PARA_CRIT_LOG("read from signal pipe returned zero\n");
-               return 0;
-       }
-       if (r < 0) {
-               if (errno == EAGAIN || errno == EINTR)
-                       return 0;
-               return -ERRNO_TO_PARA_ERROR(errno);
+       PARA_DEBUG_LOG("unblocking signal %d\n", sig);
+       sigemptyset(&set);
+       sigaddset(&set, sig);
+       sigprocmask(SIG_UNBLOCK, &set, NULL);
+}
+
+/**
+ * Return the number of the next pending signal.
+ *
+ * \param rfds The fd_set containing the signal pipe.
+ *
+ * \return On success, the number of the received signal is returned. If there
+ * is no signal currently pending, the function returns zero. On read errors
+ * from the signal pipe, the process is terminated.
+ */
+int para_next_signal(fd_set *rfds)
+{
+       size_t n;
+       int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), rfds, &n);
+
+       if (ret < 0) {
+               PARA_EMERG_LOG("%s\n", para_strerror(-ret));
+               exit(EXIT_FAILURE);
        }
-       assert(r == sizeof(s));
+       if (n == 0)
+               return 0;
+       assert(n == sizeof(s));
        PARA_DEBUG_LOG("next signal: %d\n", s);
        return s;
 }