CLEANUP: wdt: clarify the comments on the common exit path

The condition in which we reach the check for ha_panic() and
ha_stuck_warning() are not super clear, let's reformulate them.

diff --git a/src/wdt.c b/src/wdt.c
index d52fded05556e8324a3cfa8e5ea343abb421c6e1..f1159b0005a9d6bb93b1715562b4c96375a31787 100644 (file)
--- a/src/wdt.c
+++ b/src/wdt.c
@@ -175,11 +175,16 @@ void wdt_handler(int sig, siginfo_t *si, void *arg)
        }
 #endif
 
-       /* Now the interesting things begin. The timer was at least as large
-        * as the warning threshold. If the stuck bit was set, we must now
-        * panic. Otherwise we're checking if we're still context-switching
-        * or not and we'll either warn if not, or just update the ctxsw
-        * counter to check next time.
+       /* Now the interesting things begin. We're on the thread of interest.
+        * Its timer was at least as large as the warning threshold since poll
+        * was left. If it was at least as high as the panic threshold, we also
+        * have TH_FL_STUCK, which now proves that nothing is happening since
+        * the scheduler clears it for each task. We can still recheck whether
+        * the scheduler looks alive and get away with all of this if we've got
+        * a proof that it's making forward progress. If stuck, we have to die,
+        * otherwise we just send a warning. In short, is_sched_alive() serves
+        * as a ping to detect the warning condition while TH_FL_STUCK works
+        * the same but for a panic condition.
         */
        if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_STUCK)
                ha_panic();