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| -rw-r--r-- | idle.c | 178 |
1 files changed, 178 insertions, 0 deletions
@@ -0,0 +1,178 @@ +/* + * idle.c -- pause code for fetchmail + * + * For license terms, see the file COPYING in this directory. + */ +#include "config.h" + +#include <stdio.h> +#if defined(STDC_HEADERS) +#include <stdlib.h> +#endif +#if defined(HAVE_UNISTD_H) +#include <unistd.h> +#endif +#include <signal.h> +#include <errno.h> +#include <sys/time.h> + +#include "fetchmail.h" +#include "i18n.h" + +volatile int lastsig; /* last signal received */ + +#ifdef SLEEP_WITH_ALARM +/* + * The function of this variable is to remove the window during which a + * SIGALRM can hose the code (ALARM is triggered *before* pause() is called). + * This is a bit of a kluge; the real right thing would use sigprocmask(), + * sigsuspend(). This workaround lets the interval timer trigger the first + * alarm after the required interval and will then generate alarms all 5 + * seconds, until it is certain, that the critical section (ie., the window) + * is left. + */ +#if defined(STDC_HEADERS) +static sig_atomic_t alarm_latch = FALSE; +#else +/* assume int can be written in one atomic operation on non ANSI-C systems */ +static int alarm_latch = FALSE; +#endif + +RETSIGTYPE gotsigalrm(sig) +int sig; +{ + signal(sig, gotsigalrm); + lastsig = sig; + alarm_latch = TRUE; +} +#endif /* SLEEP_WITH_ALARM */ + +#ifdef __EMX__ +/* Various EMX-specific definitions */ +static int itimerflag; + +void itimerthread(void* dummy) +{ + if (outlevel >= O_VERBOSE) + report(stderr, + _("fetchmail: thread sleeping for %d sec.\n"), poll_interval); + while(1) + { + _sleep2(poll_interval*1000); + kill((getpid()), SIGALRM); + } +} +#endif + +RETSIGTYPE donothing(int sig) {signal(sig, donothing); lastsig = sig;} + +int idle(int seconds) +/* time for a pause in the action; return TRUE if awakened by signal */ +{ + int awoken = FALSE; + + /* + * With this simple hack, we make it possible for a foreground + * fetchmail to wake up one in daemon mode. What we want is the + * side effect of interrupting any sleep that may be going on, + * forcing fetchmail to re-poll its hosts. The second line is + * for people who think all system daemons wake up on SIGHUP. + */ + signal(SIGUSR1, donothing); + if (!getuid()) + signal(SIGHUP, donothing); + +#ifndef __EMX__ +#ifdef SLEEP_WITH_ALARM /* not normally on */ + /* + * We can't use sleep(3) here because we need an alarm(3) + * equivalent in order to implement server nonresponse timeout. + * We'll just assume setitimer(2) is available since fetchmail + * has to have a BSDoid socket layer to work at all. + */ + /* + * This code stopped working under glibc-2, apparently due + * to the change in signal(2) semantics. (The siginterrupt + * line, added later, should fix this problem.) John Stracke + * <francis@netscape.com> wrote: + * + * The problem seems to be that, after hitting the interval + * timer while talking to the server, the process no longer + * responds to SIGALRM. I put in printf()s to see when it + * reached the pause() for the poll interval, and I checked + * the return from setitimer(), and everything seemed to be + * working fine, except that the pause() just ignored SIGALRM. + * I thought maybe the itimer wasn't being fired, so I hit + * it with a SIGALRM from the command line, and it ignored + * that, too. SIGUSR1 woke it up just fine, and it proceeded + * to repoll--but, when the dummy server didn't respond, it + * never timed out, and SIGALRM wouldn't make it. + * + * (continued below...) + */ + { + struct itimerval ntimeout; + + ntimeout.it_interval.tv_sec = 5; /* repeat alarm every 5 secs */ + ntimeout.it_interval.tv_usec = 0; + ntimeout.it_value.tv_sec = seconds; + ntimeout.it_value.tv_usec = 0; + + siginterrupt(SIGALRM, 1); + alarm_latch = FALSE; + signal(SIGALRM, gotsigalrm); /* first trap signals */ + setitimer(ITIMER_REAL,&ntimeout,NULL); /* then start timer */ + /* there is a very small window between the next two lines */ + /* which could result in a deadlock. But this will now be */ + /* caught by periodical alarms (see it_interval) */ + if (!alarm_latch) + pause(); + /* stop timer */ + ntimeout.it_interval.tv_sec = ntimeout.it_interval.tv_usec = 0; + ntimeout.it_value.tv_sec = ntimeout.it_value.tv_usec = 0; + setitimer(ITIMER_REAL,&ntimeout,NULL); /* now stop timer */ + signal(SIGALRM, SIG_IGN); + } +#else + /* + * So the workaround I used is to make it sleep by using + * select() instead of setitimer()/pause(). select() is + * perfectly happy being called with a timeout and + * no file descriptors; it just sleeps until it hits the + * timeout. The only concern I had was that it might + * implement its timeout with SIGALRM--there are some + * Unices where this is done, because select() is a library + * function--but apparently not. + */ + { + struct timeval timeout; + + timeout.tv_sec = run.poll_interval; + timeout.tv_usec = 0; + do { + lastsig = 0; + select(0,0,0,0, &timeout); + } while (lastsig == SIGCHLD); + } +#endif +#else /* EMX */ + alarm_latch = FALSE; + signal(SIGALRM, gotsigalrm); + _beginthread(itimerthread, NULL, 32768, NULL); + /* see similar code above */ + if (!alarm_latch) + pause(); + signal(SIGALRM, SIG_IGN); +#endif /* ! EMX */ + if (lastsig == SIGUSR1 || ((seconds && !getuid()) && lastsig == SIGHUP)) + awoken = TRUE; + + /* now lock out interrupts again */ + signal(SIGUSR1, SIG_IGN); + if (!getuid()) + signal(SIGHUP, SIG_IGN); + + return(awoken ? lastsig : 0); +} + +/* idle.c ends here */ |