util/log: Add a MESA_LOG_LEVEL environment variable

This lets us control how much logging we want Mesa to do, which is
useful in CI where we don't want to collect lots of log spam that then
has to be saved somewhere.

Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37203>

docs/envvars.rst

@@ -81,6 +81,10 @@ Core Mesa environment variables
    purposes (e.g. for driconf option matching, logging, artifact storage,
    etc.).
 
+.. envvar:: MESA_LOG_LEVEL
+
+   specifies the maximum log level
+
 .. envvar:: MESA_LOG_FILE
 
    specifies a file name for logging all errors, warnings, etc., rather

src/util/log.c

@@ -67,8 +67,35 @@ static const struct debug_control mesa_log_control_options[] = {
    { NULL, 0 },
 };
 
+static inline const char *
+level_to_str(enum mesa_log_level l)
+{
+   switch (l) {
+   case MESA_LOG_ERROR: return "error";
+   case MESA_LOG_WARN: return "warning";
+   case MESA_LOG_INFO: return "info";
+   case MESA_LOG_DEBUG: return "debug";
+   case MESA_NUM_LOG_LEVELS:
+      break;
+   }
+
+   UNREACHABLE("bad mesa_log_level");
+}
+
+static enum mesa_log_level
+level_from_str(const char *str)
+{
+   for (unsigned l = 0; l < MESA_NUM_LOG_LEVELS; l++) {
+      if (strcmp(level_to_str(l), str) == 0)
+         return l;
+   }
+
+   return MESA_NUM_LOG_LEVELS;
+}
+
 static uint32_t mesa_log_control;
 static FILE *mesa_log_file;
+static enum mesa_log_level mesa_max_log_level;
 
 static void
 mesa_log_init_once(void)
@@ -91,6 +118,11 @@ mesa_log_init_once(void)
 #endif
    }
 
+   mesa_max_log_level = MESA_DEFAULT_LOG_LEVEL;
+   const char *log_level = os_get_option("MESA_LOG_LEVEL");
+   if (log_level != NULL)
+      mesa_max_log_level = level_from_str(log_level);
+
    mesa_log_file = stderr;
 
 #if !DETECT_OS_WINDOWS
@@ -119,6 +151,20 @@ mesa_log_init(void)
    call_once(&once, mesa_log_init_once);
 }
 
+static void
+mesa_warn_invalid_level_once(void)
+{
+   const char *log_level = os_get_option("MESA_LOG_LEVEL");
+   mesa_logw("Invalid log level: \"%s\"", log_level);
+}
+
+static void
+mesa_warn_invalid_level(void)
+{
+   static once_flag once = ONCE_FLAG_INIT;
+   call_once(&once, mesa_warn_invalid_level_once);
+}
+
 void
 mesa_log_if_debug(enum mesa_log_level level, const char *outputString)
 {
@@ -147,19 +193,6 @@ mesa_log_if_debug(enum mesa_log_level level, const char *outputString)
       mesa_log(level, "Mesa", "%s", outputString);
 }
 
-static inline const char *
-level_to_str(enum mesa_log_level l)
-{
-   switch (l) {
-   case MESA_LOG_ERROR: return "error";
-   case MESA_LOG_WARN: return "warning";
-   case MESA_LOG_INFO: return "info";
-   case MESA_LOG_DEBUG: return "debug";
-   }
-
-   UNREACHABLE("bad mesa_log_level");
-}
-
 enum logger_vasnprintf_affix {
    LOGGER_VASNPRINTF_AFFIX_TAG = 1 << 0,
    LOGGER_VASNPRINTF_AFFIX_LEVEL = 1 << 1,
@@ -270,6 +303,8 @@ level_to_syslog(enum mesa_log_level l)
    case MESA_LOG_WARN: return LOG_WARNING;
    case MESA_LOG_INFO: return LOG_INFO;
    case MESA_LOG_DEBUG: return LOG_DEBUG;
+   case MESA_NUM_LOG_LEVELS:
+      break;
    }
 
    UNREACHABLE("bad mesa_log_level");
@@ -303,6 +338,8 @@ level_to_android(enum mesa_log_level l)
    case MESA_LOG_WARN: return ANDROID_LOG_WARN;
    case MESA_LOG_INFO: return ANDROID_LOG_INFO;
    case MESA_LOG_DEBUG: return ANDROID_LOG_DEBUG;
+   case MESA_NUM_LOG_LEVELS:
+      break;
    }
 
    UNREACHABLE("bad mesa_log_level");
@@ -405,6 +442,17 @@ mesa_log_v(enum mesa_log_level level, const char *tag, const char *format,
 
    mesa_log_init();
 
+   if (unlikely(mesa_max_log_level >= MESA_NUM_LOG_LEVELS)) {
+      /* Set to the default since this function will call back into mesa_log()
+       * and we don't want to recurse back into the once.
+       */
+      mesa_max_log_level = MESA_DEFAULT_LOG_LEVEL;
+      mesa_warn_invalid_level();
+   }
+
+   if (level > mesa_max_log_level)
+      return;
+
    for (uint32_t i = 0; i < ARRAY_SIZE(loggers); i++) {
       if (mesa_log_control & loggers[i].bit) {
          va_list copy;

src/util/log.h

@@ -42,8 +42,16 @@ enum mesa_log_level {
    MESA_LOG_WARN,
    MESA_LOG_INFO,
    MESA_LOG_DEBUG,
+
+   MESA_NUM_LOG_LEVELS,
 };
 
+#if MESA_DEBUG
+#define MESA_DEFAULT_LOG_LEVEL MESA_LOG_DEBUG
+#else
+#define MESA_DEFAULT_LOG_LEVEL MESA_LOG_INFO
+#endif
+
 #define MAX_LOG_MESSAGE_LENGTH 4096
 
 FILE *