watchdog: add setting to configure pretimeout governor

src/shared/watchdog.c

@@ -22,6 +22,7 @@ static usec_t watchdog_timeout; /* 0 → close device and USEC_INFINITY → don'
 static usec_t watchdog_pretimeout; /* 0 → disable pretimeout and USEC_INFINITY → don't change pretimeout */
 static usec_t watchdog_last_ping = USEC_INFINITY;
 static bool watchdog_supports_pretimeout = false; /* Depends on kernel state that might change at runtime */
+static char *watchdog_pretimeout_governor = NULL;
 
 /* Starting from kernel version 4.5, the maximum allowable watchdog timeout is
  * UINT_MAX/1000U seconds (since internal calculations are done in milliseconds
@@ -76,6 +77,28 @@ static int get_pretimeout_governor(char **ret_gov) {
         return 0;
 }
 
+static int set_pretimeout_governor(const char *governor) {
+        _cleanup_free_ char *sys_fn = NULL;
+        int r;
+
+        if (isempty(governor))
+                return 0; /* Nothing to do */
+
+        r = get_watchdog_sysfs_path("pretimeout_governor", &sys_fn);
+        if (r < 0)
+                return r;
+
+        log_info("Watchdog: setting pretimeout_governor to '%s' via '%s'", governor, sys_fn);
+
+        r = write_string_file(sys_fn,
+                              governor,
+                              WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_VERIFY_IGNORE_NEWLINE);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set pretimeout_governor to '%s': %m", governor);
+
+        return r;
+}
+
 static int watchdog_set_enable(bool enable) {
         int flags = enable ? WDIOS_ENABLECARD : WDIOS_DISABLECARD;
 
@@ -194,6 +217,9 @@ static int update_pretimeout(void) {
          * might have been unloaded. */
         watchdog_supports_pretimeout = false;
 
+        /* Update the pretimeout governor as well */
+        (void) set_pretimeout_governor(watchdog_pretimeout_governor);
+
         r = get_pretimeout_governor(&governor);
         if (r < 0)
                 return log_warning_errno(r, "Watchdog: failed to read pretimeout governor: %m");
@@ -362,6 +388,13 @@ int watchdog_setup_pretimeout(usec_t timeout) {
         return update_pretimeout();
 }
 
+int watchdog_setup_pretimeout_governor(const char *governor) {
+        if (free_and_strdup(&watchdog_pretimeout_governor, governor) < 0)
+                return -ENOMEM;
+
+        return set_pretimeout_governor(watchdog_pretimeout_governor);
+}
+
 static usec_t calc_timeout(void) {
         /* Calculate the effective timeout which accounts for the watchdog
          * pretimeout if configured and supported. */

src/shared/watchdog.h

@@ -9,6 +9,7 @@
 int watchdog_set_device(const char *path);
 int watchdog_setup(usec_t timeout);
 int watchdog_setup_pretimeout(usec_t usec);
+int watchdog_setup_pretimeout_governor(const char *governor);
 int watchdog_ping(void);
 void watchdog_close(bool disarm);
 usec_t watchdog_runtime_wait(void);