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Built-in watchdog: on SIGPWR, exit main loop and prepare for SIGTERM

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When Finit enters shutdown/reboot we need to advise any watchdogd that
we are going down *before* we unmount any file systems.  This to let
the user save any state, e.g. reboot counters, to disk.  Right before
we call reboot() in Finit we send SIGTERM to the watchdogd to give it
the chance to use the WDT to reboot the system.

The WDT cricuitry on embedded systems is often connected to the RESETn
logic of all relevant board compoents, whereas reboot() only reboots the
SoC with the CPU.  Hence, a WDT reboot is more efficient and more like a
regular power cycle, which users of embedded systems often want.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>
This commit is contained in:
Joachim Nilsson
2017-12-28 20:24:32 +01:00
parent e1bb5e3396
commit c82a2ce215
1 changed files with 25 additions and 6 deletions
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src/watchdog.c
+25 -6
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@@ -31,15 +31,19 @@
int running = 1;
int handover = 0;
int shutdown = 0;
static void sighandler(int signo)
{
if (signo == SIGTERM)
handover = 1;
if (signo == SIGPWR)
shutdown = 1;
running = 0;
}
static int init(char *progname, char *devnode, int timeout)
static int init(char *progname, char *devnode)
{
int fd;
@@ -51,20 +55,28 @@ static int init(char *progname, char *devnode, int timeout)
if (fd == -1)
return -1;
ioctl(fd, WDIOC_SETTIMEOUT, &timeout);
return fd;
}
static int loop(int fd, int period)
static int loop(int fd, int timeout)
{
int dummy = 0;
int period = timeout / 2;
ioctl(fd, WDIOC_SETTIMEOUT, &timeout);
while (running) {
ioctl(fd, WDIOC_KEEPALIVE, &dummy);
sleep(period);
}
/* System is going down, prepare to reboot system on TERM */
if (shutdown) {
timeout /= 3;
ioctl(fd, WDIOC_SETTIMEOUT, &timeout);
}
/* External watchdogd wants to take over ... */
if (handover) {
ioctl(fd, WDIOC_KEEPALIVE, &dummy);
return !write(fd, "V", 1);
@@ -81,13 +93,20 @@ int watchdog(char *progname)
if (pid == 0) {
int fd, ret;
fd = init(progname, WDT_DEVNODE, WDT_TIMEOUT);
fd = init(progname, WDT_DEVNODE);
if (fd == -1) {
_pe("Failed connecting to watchdog %s", WDT_DEVNODE);
_exit(1);
}
ret = loop(fd, WDT_TIMEOUT / 2);
ret = loop(fd, WDT_TIMEOUT);
while (!handover) {
/* Waiting for SIGTERM ... */
sleep(1);
/* Set lowest possible timeout on SIGTERM */
ioctl(fd, WDIOC_SETTIMEOUT, &shutdown);
}
close(fd);
_exit(ret);