Author: mjg
Date: Wed Dec 5 16:43:03 2018
New Revision: 341593
URL: https://svnweb.freebsd.org/changeset/base/341593
Log:
sx: retire SX_NOADAPTIVE
The flag is not used by anything for years and supporting it requires an
explicit read from the lock when entering slow path.
Flag value is left unused on purpose.
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/contrib/vchiq/interface/compat/vchi_bsd.h
head/sys/kern/kern_sx.c
head/sys/sys/sx.h
Modified: head/sys/contrib/vchiq/interface/compat/vchi_bsd.h
==============================================================================
--- head/sys/contrib/vchiq/interface/compat/vchi_bsd.h Wed Dec 5 15:56:44
2018 (r341592)
+++ head/sys/contrib/vchiq/interface/compat/vchi_bsd.h Wed Dec 5 16:43:03
2018 (r341593)
@@ -162,10 +162,6 @@ struct mutex {
*/
typedef struct rwlock rwlock_t;
-#if defined(SX_ADAPTIVESPIN) && !defined(SX_NOADAPTIVE)
-#define SX_NOADAPTIVE SX_ADAPTIVESPIN
-#endif
-
#define DEFINE_RWLOCK(name) \
struct rwlock name; \
SX_SYSINIT(name, &name, #name)
Modified: head/sys/kern/kern_sx.c
==============================================================================
--- head/sys/kern/kern_sx.c Wed Dec 5 15:56:44 2018 (r341592)
+++ head/sys/kern/kern_sx.c Wed Dec 5 16:43:03 2018 (r341593)
@@ -71,8 +71,6 @@ __FBSDID("$FreeBSD$");
#define ADAPTIVE_SX
#endif
-CTASSERT((SX_NOADAPTIVE & LO_CLASSFLAGS) == SX_NOADAPTIVE);
-
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
PMC_SOFT_DECLARE( , , lock, failed);
@@ -233,7 +231,7 @@ sx_init_flags(struct sx *sx, const char *description,
int flags;
MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK |
- SX_NOPROFILE | SX_NOADAPTIVE | SX_NEW)) == 0);
+ SX_NOPROFILE | SX_NEW)) == 0);
ASSERT_ATOMIC_LOAD_PTR(sx->sx_lock,
("%s: sx_lock not aligned for %s: %p", __func__, description,
&sx->sx_lock));
@@ -252,7 +250,6 @@ sx_init_flags(struct sx *sx, const char *description,
if (opts & SX_NEW)
flags |= LO_NEW;
- flags |= opts & SX_NOADAPTIVE;
lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags);
sx->sx_lock = SX_LOCK_UNLOCKED;
sx->sx_recurse = 0;
@@ -572,7 +569,6 @@ _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LO
volatile struct thread *owner;
u_int i, n, spintries = 0;
enum { READERS, WRITER } sleep_reason = READERS;
- bool adaptive;
bool in_critical = false;
#endif
#ifdef LOCK_PROFILING
@@ -642,10 +638,6 @@ _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LO
CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
sx->lock_object.lo_name, (void *)sx->sx_lock, file, line);
-#ifdef ADAPTIVE_SX
- adaptive = ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0);
-#endif
-
#ifdef HWPMC_HOOKS
PMC_SOFT_CALL( , , lock, failed);
#endif
@@ -669,8 +661,6 @@ _sx_xlock_hard(struct sx *sx, uintptr_t x, int opts LO
lda.spin_cnt++;
#endif
#ifdef ADAPTIVE_SX
- if (__predict_false(!adaptive))
- goto sleepq;
/*
* If the lock is write locked and the owner is
* running on another CPU, spin until the owner stops
@@ -762,20 +752,18 @@ retry_sleepq:
* chain lock. If so, drop the sleep queue lock and try
* again.
*/
- if (adaptive) {
- if (!(x & SX_LOCK_SHARED)) {
- owner = (struct thread *)SX_OWNER(x);
- if (TD_IS_RUNNING(owner)) {
- sleepq_release(&sx->lock_object);
- sx_drop_critical(x, &in_critical,
- &extra_work);
- continue;
- }
- } else if (SX_SHARERS(x) > 0 && sleep_reason == WRITER)
{
+ if (!(x & SX_LOCK_SHARED)) {
+ owner = (struct thread *)SX_OWNER(x);
+ if (TD_IS_RUNNING(owner)) {
sleepq_release(&sx->lock_object);
- sx_drop_critical(x, &in_critical, &extra_work);
+ sx_drop_critical(x, &in_critical,
+ &extra_work);
continue;
}
+ } else if (SX_SHARERS(x) > 0 && sleep_reason == WRITER) {
+ sleepq_release(&sx->lock_object);
+ sx_drop_critical(x, &in_critical, &extra_work);
+ continue;
}
#endif
@@ -1021,7 +1009,6 @@ _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LO
#ifdef ADAPTIVE_SX
volatile struct thread *owner;
u_int i, n, spintries = 0;
- bool adaptive;
#endif
#ifdef LOCK_PROFILING
uint64_t waittime = 0;
@@ -1066,10 +1053,6 @@ _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LO
lock_delay_arg_init(&lda, NULL);
#endif
-#ifdef ADAPTIVE_SX
- adaptive = ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0);
-#endif
-
#ifdef HWPMC_HOOKS
PMC_SOFT_CALL( , , lock, failed);
#endif
@@ -1095,9 +1078,6 @@ _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LO
#endif
#ifdef ADAPTIVE_SX
- if (__predict_false(!adaptive))
- goto sleepq;
-
/*
* If the owner is running on another CPU, spin until
* the owner stops running or the state of the lock
@@ -1154,7 +1134,6 @@ _sx_slock_hard(struct sx *sx, int opts, uintptr_t x LO
continue;
}
}
-sleepq:
#endif
/*
@@ -1176,7 +1155,7 @@ retry_sleepq:
* the owner stops running or the state of the lock
* changes.
*/
- if (!(x & SX_LOCK_SHARED) && adaptive) {
+ if (!(x & SX_LOCK_SHARED)) {
owner = (struct thread *)SX_OWNER(x);
if (TD_IS_RUNNING(owner)) {
sleepq_release(&sx->lock_object);
Modified: head/sys/sys/sx.h
==============================================================================
--- head/sys/sys/sx.h Wed Dec 5 15:56:44 2018 (r341592)
+++ head/sys/sys/sx.h Wed Dec 5 16:43:03 2018 (r341593)
@@ -273,7 +273,6 @@ __sx_xunlock(struct sx *sx, struct thread *td, const c
#define SX_NOPROFILE 0x02
#define SX_NOWITNESS 0x04
#define SX_QUIET 0x08
-#define SX_NOADAPTIVE 0x10
#define SX_RECURSE 0x20
#define SX_NEW 0x40
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