svn commit: r365237 - head/sys/kern

[Hans Petter Selasky]

Author: hselasky
Date: Wed Sep  2 09:44:00 2020
New Revision: 365237
URL: https://svnweb.freebsd.org/changeset/base/365237

Log:
  Micro optimise _callout_stop_safe() by removing dead code.
  
  The CS_DRAIN flag cannot be set at the same time like the async-drain function
  pointer is set. These are orthogonal features. Assert this at the beginning
  of the function.
  
  Before:
          if (flags & CS_DRAIN) {
                  /* FALLTHROUGH */
          } else if (xxx) {
                  return yyy;
          }
          if (drain) {
                  zzz = drain;
          }
  After:
          if (flags & CS_DRAIN) {
                  /* FALLTHROUGH */
          } else if (xxx) {
                  return yyy;
          } else {
                  if (drain) {
                          zzz = drain;
                  }
          }
  
  Reviewed by:	markj@
  Tested by:	callout_test
  Differential Revision:	https://reviews.freebsd.org/D26285
  MFC after:	1 week
  Sponsored by:	Mellanox Technologies // NVIDIA Networking

Modified:
  head/sys/kern/kern_timeout.c

Modified: head/sys/kern/kern_timeout.c
==============================================================================
--- head/sys/kern/kern_timeout.c	Wed Sep  2 09:20:40 2020	(r365236)
+++ head/sys/kern/kern_timeout.c	Wed Sep  2 09:44:00 2020	(r365237)
@@ -1075,6 +1075,9 @@ _callout_stop_safe(struct callout *c, int flags, callo
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 		    "calling %s", __func__);
 
+	KASSERT((flags & CS_DRAIN) == 0 || drain == NULL,
+	    ("Cannot set drain callback and CS_DRAIN flag at the same time"));
+
 	/*
 	 * Some old subsystems don't hold Giant while running a callout_stop(),
 	 * so just discard this check for the moment.
@@ -1270,11 +1273,12 @@ again:
 			}
 			CC_UNLOCK(cc);
 			return ((flags & CS_EXECUTING) != 0);
-		}
-		CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
-		    c, c->c_func, c->c_arg);
-		if (drain) {
-			cc_exec_drain(cc, direct) = drain;
+		} else {
+			CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
+			    c, c->c_func, c->c_arg);
+			if (drain) {
+				cc_exec_drain(cc, direct) = drain;
+			}
 		}
 		KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 		cancelled = ((flags & CS_EXECUTING) != 0);