]> Cypherpunks repositories - gostls13.git/commitdiff
runtime: commit to spinbitmutex GOEXPERIMENT
authorRhys Hiltner <rhys.hiltner@gmail.com>
Fri, 14 Mar 2025 19:38:34 +0000 (12:38 -0700)
committerGopher Robot <gobot@golang.org>
Tue, 22 Apr 2025 17:00:26 +0000 (10:00 -0700)
Use the "spinbit" mutex implementation always (including on platforms
that need to emulate atomic.Xchg8), and delete the prior "tristate"
implementations.

The exception is GOARCH=wasm, where the Go runtime does not use multiple
threads.

For #68578

Change-Id: Ifc29bbfa05071d776c23a19ae185891a03a82417
Reviewed-on: https://go-review.googlesource.com/c/go/+/658456
Auto-Submit: Rhys Hiltner <rhys.hiltner@gmail.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/internal/buildcfg/exp.go
src/internal/goexperiment/exp_spinbitmutex_off.go [deleted file]
src/internal/goexperiment/exp_spinbitmutex_on.go [deleted file]
src/internal/goexperiment/flags.go
src/runtime/lock_futex_tristate.go [deleted file]
src/runtime/lock_sema_tristate.go [deleted file]
src/runtime/lock_spinbit.go
src/runtime/runtime2.go

index ccdf465ffbba872f3f140f8479365c4ca3becf67..e36ec08a5b0232656bd3f45b61ba2079d0da813f 100644 (file)
@@ -67,8 +67,6 @@ func ParseGOEXPERIMENT(goos, goarch, goexp string) (*ExperimentFlags, error) {
                regabiSupported = true
        }
 
-       haveThreads := goarch != "wasm"
-
        // Older versions (anything before V16) of dsymutil don't handle
        // the .debug_rnglists section in DWARF5. See
        // https://github.com/golang/go/issues/26379#issuecomment-2677068742
@@ -85,7 +83,6 @@ func ParseGOEXPERIMENT(goos, goarch, goexp string) (*ExperimentFlags, error) {
                RegabiArgs:      regabiSupported,
                AliasTypeParams: true,
                SwissMap:        true,
-               SpinbitMutex:    haveThreads,
                SyncHashTrieMap: true,
                Dwarf5:          dwarf5Supported,
        }
diff --git a/src/internal/goexperiment/exp_spinbitmutex_off.go b/src/internal/goexperiment/exp_spinbitmutex_off.go
deleted file mode 100644 (file)
index 776b0dc..0000000
+++ /dev/null
@@ -1,8 +0,0 @@
-// Code generated by mkconsts.go. DO NOT EDIT.
-
-//go:build !goexperiment.spinbitmutex
-
-package goexperiment
-
-const SpinbitMutex = false
-const SpinbitMutexInt = 0
diff --git a/src/internal/goexperiment/exp_spinbitmutex_on.go b/src/internal/goexperiment/exp_spinbitmutex_on.go
deleted file mode 100644 (file)
index 8468030..0000000
+++ /dev/null
@@ -1,8 +0,0 @@
-// Code generated by mkconsts.go. DO NOT EDIT.
-
-//go:build goexperiment.spinbitmutex
-
-package goexperiment
-
-const SpinbitMutex = true
-const SpinbitMutexInt = 1
index 271fdc2b3cfae8222a0dd5523cf6902c4f9d78d2..0961764bee672140ec09b14df0d97c336e7b1d7b 100644 (file)
@@ -115,10 +115,6 @@ type Flags struct {
        // SwissMap enables the SwissTable-based map implementation.
        SwissMap bool
 
-       // SpinbitMutex enables the new "spinbit" mutex implementation on supported
-       // platforms. See https://go.dev/issue/68578.
-       SpinbitMutex bool
-
        // SyncHashTrieMap enables the HashTrieMap sync.Map implementation.
        SyncHashTrieMap bool
 
diff --git a/src/runtime/lock_futex_tristate.go b/src/runtime/lock_futex_tristate.go
deleted file mode 100644 (file)
index b7df18c..0000000
+++ /dev/null
@@ -1,138 +0,0 @@
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build (dragonfly || freebsd || linux) && !goexperiment.spinbitmutex
-
-package runtime
-
-import (
-       "internal/runtime/atomic"
-)
-
-// This implementation depends on OS-specific implementations of
-//
-//     futexsleep(addr *uint32, val uint32, ns int64)
-//             Atomically,
-//                     if *addr == val { sleep }
-//             Might be woken up spuriously; that's allowed.
-//             Don't sleep longer than ns; ns < 0 means forever.
-//
-//     futexwakeup(addr *uint32, cnt uint32)
-//             If any procs are sleeping on addr, wake up at most cnt.
-
-const (
-       mutex_unlocked = 0
-       mutex_locked   = 1
-       mutex_sleeping = 2
-
-       active_spin     = 4
-       active_spin_cnt = 30
-       passive_spin    = 1
-)
-
-// Possible lock states are mutex_unlocked, mutex_locked and mutex_sleeping.
-// mutex_sleeping means that there is presumably at least one sleeping thread.
-// Note that there can be spinning threads during all states - they do not
-// affect mutex's state.
-
-type mWaitList struct{}
-
-func lockVerifyMSize() {}
-
-func mutexContended(l *mutex) bool {
-       return atomic.Load(key32(&l.key)) > mutex_locked
-}
-
-func lock(l *mutex) {
-       lockWithRank(l, getLockRank(l))
-}
-
-func lock2(l *mutex) {
-       gp := getg()
-
-       if gp.m.locks < 0 {
-               throw("runtime·lock: lock count")
-       }
-       gp.m.locks++
-
-       // Speculative grab for lock.
-       v := atomic.Xchg(key32(&l.key), mutex_locked)
-       if v == mutex_unlocked {
-               return
-       }
-
-       // wait is either MUTEX_LOCKED or MUTEX_SLEEPING
-       // depending on whether there is a thread sleeping
-       // on this mutex. If we ever change l->key from
-       // MUTEX_SLEEPING to some other value, we must be
-       // careful to change it back to MUTEX_SLEEPING before
-       // returning, to ensure that the sleeping thread gets
-       // its wakeup call.
-       wait := v
-
-       timer := &lockTimer{lock: l}
-       timer.begin()
-       // On uniprocessors, no point spinning.
-       // On multiprocessors, spin for ACTIVE_SPIN attempts.
-       spin := 0
-       if ncpu > 1 {
-               spin = active_spin
-       }
-       for {
-               // Try for lock, spinning.
-               for i := 0; i < spin; i++ {
-                       for l.key == mutex_unlocked {
-                               if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
-                                       timer.end()
-                                       return
-                               }
-                       }
-                       procyield(active_spin_cnt)
-               }
-
-               // Try for lock, rescheduling.
-               for i := 0; i < passive_spin; i++ {
-                       for l.key == mutex_unlocked {
-                               if atomic.Cas(key32(&l.key), mutex_unlocked, wait) {
-                                       timer.end()
-                                       return
-                               }
-                       }
-                       osyield()
-               }
-
-               // Sleep.
-               v = atomic.Xchg(key32(&l.key), mutex_sleeping)
-               if v == mutex_unlocked {
-                       timer.end()
-                       return
-               }
-               wait = mutex_sleeping
-               futexsleep(key32(&l.key), mutex_sleeping, -1)
-       }
-}
-
-func unlock(l *mutex) {
-       unlockWithRank(l)
-}
-
-func unlock2(l *mutex) {
-       v := atomic.Xchg(key32(&l.key), mutex_unlocked)
-       if v == mutex_unlocked {
-               throw("unlock of unlocked lock")
-       }
-       if v == mutex_sleeping {
-               futexwakeup(key32(&l.key), 1)
-       }
-
-       gp := getg()
-       gp.m.mLockProfile.recordUnlock(l)
-       gp.m.locks--
-       if gp.m.locks < 0 {
-               throw("runtime·unlock: lock count")
-       }
-       if gp.m.locks == 0 && gp.preempt { // restore the preemption request in case we've cleared it in newstack
-               gp.stackguard0 = stackPreempt
-       }
-}
diff --git a/src/runtime/lock_sema_tristate.go b/src/runtime/lock_sema_tristate.go
deleted file mode 100644 (file)
index 4375791..0000000
+++ /dev/null
@@ -1,148 +0,0 @@
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build (aix || darwin || netbsd || openbsd || plan9 || solaris || windows) && !goexperiment.spinbitmutex
-
-package runtime
-
-import (
-       "internal/runtime/atomic"
-       "unsafe"
-)
-
-// This implementation depends on OS-specific implementations of
-//
-//     func semacreate(mp *m)
-//             Create a semaphore for mp, if it does not already have one.
-//
-//     func semasleep(ns int64) int32
-//             If ns < 0, acquire m's semaphore and return 0.
-//             If ns >= 0, try to acquire m's semaphore for at most ns nanoseconds.
-//             Return 0 if the semaphore was acquired, -1 if interrupted or timed out.
-//
-//     func semawakeup(mp *m)
-//             Wake up mp, which is or will soon be sleeping on its semaphore.
-const (
-       active_spin     = 4
-       active_spin_cnt = 30
-       passive_spin    = 1
-)
-
-// mWaitList is part of the M struct, and holds the list of Ms that are waiting
-// for a particular runtime.mutex.
-//
-// When an M is unable to immediately obtain a lock, it adds itself to the list
-// of Ms waiting for the lock. It does that via this struct's next field,
-// forming a singly-linked list with the mutex's key field pointing to the head
-// of the list.
-type mWaitList struct {
-       next muintptr // next m waiting for lock
-}
-
-func lockVerifyMSize() {}
-
-func mutexContended(l *mutex) bool {
-       return atomic.Loaduintptr(&l.key) > locked
-}
-
-func lock(l *mutex) {
-       lockWithRank(l, getLockRank(l))
-}
-
-func lock2(l *mutex) {
-       gp := getg()
-       if gp.m.locks < 0 {
-               throw("runtime·lock: lock count")
-       }
-       gp.m.locks++
-
-       // Speculative grab for lock.
-       if atomic.Casuintptr(&l.key, 0, locked) {
-               return
-       }
-       semacreate(gp.m)
-
-       timer := &lockTimer{lock: l}
-       timer.begin()
-       // On uniprocessor's, no point spinning.
-       // On multiprocessors, spin for ACTIVE_SPIN attempts.
-       spin := 0
-       if ncpu > 1 {
-               spin = active_spin
-       }
-Loop:
-       for i := 0; ; i++ {
-               v := atomic.Loaduintptr(&l.key)
-               if v&locked == 0 {
-                       // Unlocked. Try to lock.
-                       if atomic.Casuintptr(&l.key, v, v|locked) {
-                               timer.end()
-                               return
-                       }
-                       i = 0
-               }
-               if i < spin {
-                       procyield(active_spin_cnt)
-               } else if i < spin+passive_spin {
-                       osyield()
-               } else {
-                       // Someone else has it.
-                       // l.key points to a linked list of M's waiting
-                       // for this lock, chained through m.mWaitList.next.
-                       // Queue this M.
-                       for {
-                               gp.m.mWaitList.next = muintptr(v &^ locked)
-                               if atomic.Casuintptr(&l.key, v, uintptr(unsafe.Pointer(gp.m))|locked) {
-                                       break
-                               }
-                               v = atomic.Loaduintptr(&l.key)
-                               if v&locked == 0 {
-                                       continue Loop
-                               }
-                       }
-                       if v&locked != 0 {
-                               // Queued. Wait.
-                               semasleep(-1)
-                               i = 0
-                       }
-               }
-       }
-}
-
-func unlock(l *mutex) {
-       unlockWithRank(l)
-}
-
-// We might not be holding a p in this code.
-//
-//go:nowritebarrier
-func unlock2(l *mutex) {
-       gp := getg()
-       var mp *m
-       for {
-               v := atomic.Loaduintptr(&l.key)
-               if v == locked {
-                       if atomic.Casuintptr(&l.key, locked, 0) {
-                               break
-                       }
-               } else {
-                       // Other M's are waiting for the lock.
-                       // Dequeue an M.
-                       mp = muintptr(v &^ locked).ptr()
-                       if atomic.Casuintptr(&l.key, v, uintptr(mp.mWaitList.next)) {
-                               // Dequeued an M.  Wake it.
-                               semawakeup(mp) // no use of mp after this point; it's awake
-                               break
-                       }
-               }
-       }
-       gp.m.mLockProfile.recordUnlock(l)
-       gp.m.locks--
-       if gp.m.locks < 0 {
-               throw("runtime·unlock: lock count")
-       }
-       if gp.m.locks == 0 && gp.preempt { // restore the preemption request in case we've cleared it in newstack
-               gp.stackguard0 = stackPreempt
-       }
-}
index 7b7bc651ad95897dd134cf6c0764bd108460487d..9bca4bd8243c5ba1485172421fd54124d23c162f 100644 (file)
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || plan9 || solaris || windows) && goexperiment.spinbitmutex
+//go:build !wasm
 
 package runtime
 
index 27d14b890bd654708d7f630c4621c1e34fe738f3..f7371c450bd93c5007b0bc4a80d0a38856bde67e 100644 (file)
@@ -8,7 +8,6 @@ import (
        "internal/abi"
        "internal/chacha8rand"
        "internal/goarch"
-       "internal/goexperiment"
        "internal/runtime/atomic"
        "internal/runtime/sys"
        "unsafe"
@@ -628,9 +627,9 @@ type mPadded struct {
 
        // Size the runtime.m structure so it fits in the 2048-byte size class, and
        // not in the next-smallest (1792-byte) size class. That leaves the 11 low
-       // bits of muintptr values available for flags, as required for
-       // GOEXPERIMENT=spinbitmutex.
-       _ [goexperiment.SpinbitMutexInt * (2048 - mallocHeaderSize - mRedZoneSize - unsafe.Sizeof(m{}))]byte
+       // bits of muintptr values available for flags, as required by
+       // lock_spinbit.go.
+       _ [(1 - goarch.IsWasm) * (2048 - mallocHeaderSize - mRedZoneSize - unsafe.Sizeof(m{}))]byte
 }
 
 type p struct {