[logging] Add LL_CRUCIAL logging priority. JB#36274

Now and then there are issues that can't be easily diagnosed without
logging and the causes might be rare enough that manually enabling
extra logging after hitting the problem does not accomplish anything.

Provide separate logging priority that is easy to spot and demote
from mce code base once some specific issue has been found and fixed.

mce-log.c

@@ -78,13 +78,13 @@ static void timestamp(struct timeval *tv)
  *
  * @return log level clipped to LL_CRIT ... LL_DEBUG range
  */
-static loglevel_t mce_log_level_normalize(loglevel_t loglevel)
+static loglevel_t mce_log_level_clip(loglevel_t loglevel)
 {
-	if( loglevel < LL_EXTRA ) {
-		loglevel = LL_EXTRA;
+	if( loglevel <= LL_MINIMUM ) {
+		loglevel = LL_MINIMUM;
 	}
-	else if( loglevel > LL_DEBUG ) {
-		loglevel = LL_DEBUG;
+	else if( loglevel > LL_MAXIMUM ) {
+		loglevel = LL_MAXIMUM;
 	}
 	return loglevel;
 }
@@ -99,6 +99,7 @@ static const char *mce_log_level_tag(loglevel_t loglevel)
 {
 	const char *res = "?";
 	switch( loglevel ) {
+	case LL_CRUCIAL:res = "T"; break;
 	case LL_EXTRA:  res = "X"; break;
 	case LL_CRIT:   res = "C"; break;
 	case LL_ERR:    res = "E"; break;
@@ -169,7 +170,7 @@ void mce_log_file(loglevel_t loglevel, const char *const file,
 {
 	va_list args;
 
-	loglevel = mce_log_level_normalize(loglevel);
+	loglevel = mce_log_level_clip(loglevel);
 
 	if( mce_log_p_(loglevel, file, function) ) {
 		gchar *msg = 0;
@@ -193,9 +194,16 @@ void mce_log_file(loglevel_t loglevel, const char *const file,
 				mce_log_level_tag(loglevel),
 				msg);
 		} else {
-			/* LL_EXTRA = devel flavor notice */
-			if( loglevel == LL_EXTRA )
+			/* Use NOTICE priority when reporting LL_EXTRA
+			 * and LL_CRUCIAL logging */
+			switch( loglevel ) {
+			case LL_EXTRA:
+			case LL_CRUCIAL:
 				loglevel = LL_NOTICE;
+				break;
+			default:
+				break;
+			}
 
 			/* loglevels are subset of syslog priorities, so
 			 * we can use loglevel as is for syslog priority */
@@ -310,7 +318,7 @@ static bool mce_log_check_pattern(const char *func)
  *
  * @return 1 if logging at givel level is enabled, 0 if not
  */
-int mce_log_p_(const loglevel_t loglevel,
+int mce_log_p_(loglevel_t loglevel,
 	       const char *const file,
 	       const char *const func)
 {
@@ -321,8 +329,15 @@ int mce_log_p_(const loglevel_t loglevel,
 			return true;
 	}
 
-	if( loglevel < LL_EXTRA )
-		return logverbosity >= LL_NOTICE;
+	/* LL_EXTRA & LL_CRUCIAL are evaluated as WARNING level */
+	switch( loglevel ) {
+	case LL_EXTRA:
+	case LL_CRUCIAL:
+		loglevel = LL_WARN;;
+		break;
+	default:
+		break;
+	}
 
 	return logverbosity >= loglevel;
 }

mce-log.h

@@ -48,14 +48,18 @@ typedef enum {
 	LL_MAXIMUM = LOG_DEBUG,		/**< Minimum for bounds checking */
 	LL_MINIMUM = LOG_EMERG,		/**< Maximum for bounds checking */
 
+	LL_CRUCIAL = LOG_EMERG,		/**< Elevated priority for solving
+					 *   problems that require logs from
+					 *   the whole user base. Should be
+					 *   downgraded as soon as possible. */
 } loglevel_t;
 
 # ifdef OSSOLOG_COMPILE
 void mce_log_add_pattern(const char *pat);
 void mce_log_set_verbosity(int verbosity);
 int  mce_log_get_verbosity(void);
 
-int  mce_log_p_(const loglevel_t loglevel,
+int  mce_log_p_(loglevel_t loglevel,
 		const char *const file, const char *const function);
 
 void mce_log_file(loglevel_t loglevel, const char *const file,