4 files changed, 7 insertions, 7 deletions

diff --git a/sys/amd64/conf/GENERIC b/sys/amd64/conf/GENERIC
index 4cd44a467ae85..87ca19f7f2fc3 100644
--- a/sys/amd64/conf/GENERIC
+++ b/sys/amd64/conf/GENERIC
@@ -28,7 +28,6 @@ ident		GENERIC
 makeoptions	DEBUG=-g		# Build kernel with gdb(1) debug symbols
 
 options 	SCHED_ULE		# ULE scheduler
-options 	ADAPTIVE_MUTEXES	# mutexes first spin lock, then sleep
 options 	INET			# InterNETworking
 options 	INET6			# IPv6 communications protocols
 options 	FFS			# Berkeley Fast Filesystem
diff --git a/sys/conf/NOTES b/sys/conf/NOTES
index 0ec51a5813397..6e336056fd5f5 100644
--- a/sys/conf/NOTES
+++ b/sys/conf/NOTES
@@ -169,8 +169,9 @@ options 	SMP			# Symmetric MultiProcessor Kernel
 
 # ADAPTIVE_MUTEXES changes the behavior of blocking mutexes to spin
 # if the thread that currently owns the mutex is executing on another
-# CPU.
-options 	ADAPTIVE_MUTEXES
+# CPU.  This behaviour is enabled by default, so this option can be used
+# to disable it.
+options 	NO_ADAPTIVE_MUTEXES
 
 # MUTEX_NOINLINE forces mutex operations to call functions to perform each
 # operation rather than inlining the simple cases.  This can be used to
diff --git a/sys/conf/options b/sys/conf/options
index 042a025471907..d1dcb2a719de0 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -56,7 +56,7 @@ KDB_TRACE	opt_kdb.h
 KDB_UNATTENDED	opt_kdb.h
 
 # Miscellaneous options.
-ADAPTIVE_MUTEXES
+NO_ADAPTIVE_MUTEXES
 ALQ
 CODA_COMPAT_5	opt_coda.h
 COMPAT_43	opt_compat.h
diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c
index 662cd4c6c6644..ffb75e3f6d0ed 100644
--- a/sys/kern/kern_mutex.c
+++ b/sys/kern/kern_mutex.c
@@ -421,7 +421,7 @@ _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
 {
 	struct turnstile *ts;
 	struct thread *td = curthread;
-#if defined(SMP) && defined(ADAPTIVE_MUTEXES)
+#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
 	struct thread *owner;
 #endif
 	uintptr_t v;
@@ -503,7 +503,7 @@ _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
 			continue;
 		}
 
-#if defined(SMP) && defined(ADAPTIVE_MUTEXES)
+#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
 		/*
 		 * If the current owner of the lock is executing on another
 		 * CPU, spin instead of blocking.
@@ -518,7 +518,7 @@ _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
 			}
 			continue;
 		}
-#endif	/* SMP && ADAPTIVE_MUTEXES */
+#endif	/* SMP && !NO_ADAPTIVE_MUTEXES */
 
 		/*
 		 * We definitely must sleep for this lock.