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-rw-r--r--pkg/atomicbitops/BUILD9
-rw-r--r--pkg/atomicbitops/atomicbitops.go (renamed from pkg/atomicbitops/atomic_bitops.go)31
-rw-r--r--pkg/atomicbitops/atomicbitops_amd64.s (renamed from pkg/atomicbitops/atomic_bitops_amd64.s)38
-rw-r--r--pkg/atomicbitops/atomicbitops_arm64.s (renamed from pkg/atomicbitops/atomic_bitops_arm64.s)34
-rw-r--r--pkg/atomicbitops/atomicbitops_noasm.go (renamed from pkg/atomicbitops/atomic_bitops_common.go)42
-rw-r--r--pkg/atomicbitops/atomicbitops_test.go (renamed from pkg/atomicbitops/atomic_bitops_test.go)64
-rw-r--r--pkg/sentry/mm/address_space.go23
-rw-r--r--pkg/sentry/mm/lifecycle.go11
8 files changed, 40 insertions, 212 deletions
diff --git a/pkg/atomicbitops/BUILD b/pkg/atomicbitops/BUILD
index 3948074ba..ba8b06071 100644
--- a/pkg/atomicbitops/BUILD
+++ b/pkg/atomicbitops/BUILD
@@ -5,10 +5,9 @@ package(licenses = ["notice"])
go_library(
name = "atomicbitops",
srcs = [
- "atomic_bitops.go",
- "atomic_bitops_amd64.s",
- "atomic_bitops_arm64.s",
- "atomic_bitops_common.go",
+ "atomicbitops.go",
+ "atomicbitops_amd64.s",
+ "atomicbitops_noasm.go",
],
visibility = ["//:sandbox"],
)
@@ -16,7 +15,7 @@ go_library(
go_test(
name = "atomicbitops_test",
size = "small",
- srcs = ["atomic_bitops_test.go"],
+ srcs = ["atomicbitops_test.go"],
library = ":atomicbitops",
deps = ["//pkg/sync"],
)
diff --git a/pkg/atomicbitops/atomic_bitops.go b/pkg/atomicbitops/atomicbitops.go
index fcc41a9ea..1be081719 100644
--- a/pkg/atomicbitops/atomic_bitops.go
+++ b/pkg/atomicbitops/atomicbitops.go
@@ -14,47 +14,34 @@
// +build amd64 arm64
-// Package atomicbitops provides basic bitwise operations in an atomic way.
-// The implementation on amd64 leverages the LOCK prefix directly instead of
-// relying on the generic cas primitives, and the arm64 leverages the LDAXR
-// and STLXR pair primitives.
+// Package atomicbitops provides extensions to the sync/atomic package.
//
-// WARNING: the bitwise ops provided in this package doesn't imply any memory
-// ordering. Using them to construct locks must employ proper memory barriers.
+// All read-modify-write operations implemented by this package have
+// acquire-release memory ordering (like sync/atomic).
package atomicbitops
-// AndUint32 atomically applies bitwise and operation to *addr with val.
+// AndUint32 atomically applies bitwise AND operation to *addr with val.
func AndUint32(addr *uint32, val uint32)
-// OrUint32 atomically applies bitwise or operation to *addr with val.
+// OrUint32 atomically applies bitwise OR operation to *addr with val.
func OrUint32(addr *uint32, val uint32)
-// XorUint32 atomically applies bitwise xor operation to *addr with val.
+// XorUint32 atomically applies bitwise XOR operation to *addr with val.
func XorUint32(addr *uint32, val uint32)
// CompareAndSwapUint32 is like sync/atomic.CompareAndSwapUint32, but returns
// the value previously stored at addr.
func CompareAndSwapUint32(addr *uint32, old, new uint32) uint32
-// AndUint64 atomically applies bitwise and operation to *addr with val.
+// AndUint64 atomically applies bitwise AND operation to *addr with val.
func AndUint64(addr *uint64, val uint64)
-// OrUint64 atomically applies bitwise or operation to *addr with val.
+// OrUint64 atomically applies bitwise OR operation to *addr with val.
func OrUint64(addr *uint64, val uint64)
-// XorUint64 atomically applies bitwise xor operation to *addr with val.
+// XorUint64 atomically applies bitwise XOR operation to *addr with val.
func XorUint64(addr *uint64, val uint64)
// CompareAndSwapUint64 is like sync/atomic.CompareAndSwapUint64, but returns
// the value previously stored at addr.
func CompareAndSwapUint64(addr *uint64, old, new uint64) uint64
-
-// IncUnlessZeroInt32 increments the value stored at the given address and
-// returns true; unless the value stored in the pointer is zero, in which case
-// it is left unmodified and false is returned.
-func IncUnlessZeroInt32(addr *int32) bool
-
-// DecUnlessOneInt32 decrements the value stored at the given address and
-// returns true; unless the value stored in the pointer is 1, in which case it
-// is left unmodified and false is returned.
-func DecUnlessOneInt32(addr *int32) bool
diff --git a/pkg/atomicbitops/atomic_bitops_amd64.s b/pkg/atomicbitops/atomicbitops_amd64.s
index db0972001..54c887ee5 100644
--- a/pkg/atomicbitops/atomic_bitops_amd64.s
+++ b/pkg/atomicbitops/atomicbitops_amd64.s
@@ -75,41 +75,3 @@ TEXT ·CompareAndSwapUint64(SB),$0-32
CMPXCHGQ DX, 0(DI)
MOVQ AX, ret+24(FP)
RET
-
-TEXT ·IncUnlessZeroInt32(SB),NOSPLIT,$0-9
- MOVQ addr+0(FP), DI
- MOVL 0(DI), AX
-
-retry:
- TESTL AX, AX
- JZ fail
- LEAL 1(AX), DX
- LOCK
- CMPXCHGL DX, 0(DI)
- JNZ retry
-
- SETEQ ret+8(FP)
- RET
-
-fail:
- MOVB AX, ret+8(FP)
- RET
-
-TEXT ·DecUnlessOneInt32(SB),NOSPLIT,$0-9
- MOVQ addr+0(FP), DI
- MOVL 0(DI), AX
-
-retry:
- LEAL -1(AX), DX
- TESTL DX, DX
- JZ fail
- LOCK
- CMPXCHGL DX, 0(DI)
- JNZ retry
-
- SETEQ ret+8(FP)
- RET
-
-fail:
- MOVB DX, ret+8(FP)
- RET
diff --git a/pkg/atomicbitops/atomic_bitops_arm64.s b/pkg/atomicbitops/atomicbitops_arm64.s
index 97f8808c1..5c780851b 100644
--- a/pkg/atomicbitops/atomic_bitops_arm64.s
+++ b/pkg/atomicbitops/atomicbitops_arm64.s
@@ -50,7 +50,6 @@ TEXT ·CompareAndSwapUint32(SB),$0-20
MOVD addr+0(FP), R0
MOVW old+8(FP), R1
MOVW new+12(FP), R2
-
again:
LDAXRW (R0), R3
CMPW R1, R3
@@ -95,7 +94,6 @@ TEXT ·CompareAndSwapUint64(SB),$0-32
MOVD addr+0(FP), R0
MOVD old+8(FP), R1
MOVD new+16(FP), R2
-
again:
LDAXR (R0), R3
CMP R1, R3
@@ -105,35 +103,3 @@ again:
done:
MOVD R3, prev+24(FP)
RET
-
-TEXT ·IncUnlessZeroInt32(SB),NOSPLIT,$0-9
- MOVD addr+0(FP), R0
-
-again:
- LDAXRW (R0), R1
- CBZ R1, fail
- ADDW $1, R1
- STLXRW R1, (R0), R2
- CBNZ R2, again
- MOVW $1, R2
- MOVB R2, ret+8(FP)
- RET
-fail:
- MOVB ZR, ret+8(FP)
- RET
-
-TEXT ·DecUnlessOneInt32(SB),NOSPLIT,$0-9
- MOVD addr+0(FP), R0
-
-again:
- LDAXRW (R0), R1
- SUBSW $1, R1, R1
- BEQ fail
- STLXRW R1, (R0), R2
- CBNZ R2, again
- MOVW $1, R2
- MOVB R2, ret+8(FP)
- RET
-fail:
- MOVB ZR, ret+8(FP)
- RET
diff --git a/pkg/atomicbitops/atomic_bitops_common.go b/pkg/atomicbitops/atomicbitops_noasm.go
index 85163ad62..3b2898256 100644
--- a/pkg/atomicbitops/atomic_bitops_common.go
+++ b/pkg/atomicbitops/atomicbitops_noasm.go
@@ -20,7 +20,6 @@ import (
"sync/atomic"
)
-// AndUint32 atomically applies bitwise and operation to *addr with val.
func AndUint32(addr *uint32, val uint32) {
for {
o := atomic.LoadUint32(addr)
@@ -31,7 +30,6 @@ func AndUint32(addr *uint32, val uint32) {
}
}
-// OrUint32 atomically applies bitwise or operation to *addr with val.
func OrUint32(addr *uint32, val uint32) {
for {
o := atomic.LoadUint32(addr)
@@ -42,7 +40,6 @@ func OrUint32(addr *uint32, val uint32) {
}
}
-// XorUint32 atomically applies bitwise xor operation to *addr with val.
func XorUint32(addr *uint32, val uint32) {
for {
o := atomic.LoadUint32(addr)
@@ -53,8 +50,6 @@ func XorUint32(addr *uint32, val uint32) {
}
}
-// CompareAndSwapUint32 is like sync/atomic.CompareAndSwapUint32, but returns
-// the value previously stored at addr.
func CompareAndSwapUint32(addr *uint32, old, new uint32) (prev uint32) {
for {
prev = atomic.LoadUint32(addr)
@@ -67,7 +62,6 @@ func CompareAndSwapUint32(addr *uint32, old, new uint32) (prev uint32) {
}
}
-// AndUint64 atomically applies bitwise and operation to *addr with val.
func AndUint64(addr *uint64, val uint64) {
for {
o := atomic.LoadUint64(addr)
@@ -78,7 +72,6 @@ func AndUint64(addr *uint64, val uint64) {
}
}
-// OrUint64 atomically applies bitwise or operation to *addr with val.
func OrUint64(addr *uint64, val uint64) {
for {
o := atomic.LoadUint64(addr)
@@ -89,7 +82,6 @@ func OrUint64(addr *uint64, val uint64) {
}
}
-// XorUint64 atomically applies bitwise xor operation to *addr with val.
func XorUint64(addr *uint64, val uint64) {
for {
o := atomic.LoadUint64(addr)
@@ -100,8 +92,6 @@ func XorUint64(addr *uint64, val uint64) {
}
}
-// CompareAndSwapUint64 is like sync/atomic.CompareAndSwapUint64, but returns
-// the value previously stored at addr.
func CompareAndSwapUint64(addr *uint64, old, new uint64) (prev uint64) {
for {
prev = atomic.LoadUint64(addr)
@@ -113,35 +103,3 @@ func CompareAndSwapUint64(addr *uint64, old, new uint64) (prev uint64) {
}
}
}
-
-// IncUnlessZeroInt32 increments the value stored at the given address and
-// returns true; unless the value stored in the pointer is zero, in which case
-// it is left unmodified and false is returned.
-func IncUnlessZeroInt32(addr *int32) bool {
- for {
- v := atomic.LoadInt32(addr)
- if v == 0 {
- return false
- }
-
- if atomic.CompareAndSwapInt32(addr, v, v+1) {
- return true
- }
- }
-}
-
-// DecUnlessOneInt32 decrements the value stored at the given address and
-// returns true; unless the value stored in the pointer is 1, in which case it
-// is left unmodified and false is returned.
-func DecUnlessOneInt32(addr *int32) bool {
- for {
- v := atomic.LoadInt32(addr)
- if v == 1 {
- return false
- }
-
- if atomic.CompareAndSwapInt32(addr, v, v-1) {
- return true
- }
- }
-}
diff --git a/pkg/atomicbitops/atomic_bitops_test.go b/pkg/atomicbitops/atomicbitops_test.go
index 9466d3e23..73af71bb4 100644
--- a/pkg/atomicbitops/atomic_bitops_test.go
+++ b/pkg/atomicbitops/atomicbitops_test.go
@@ -196,67 +196,3 @@ func TestCompareAndSwapUint64(t *testing.T) {
}
}
}
-
-func TestIncUnlessZeroInt32(t *testing.T) {
- for _, test := range []struct {
- initial int32
- final int32
- ret bool
- }{
- {
- initial: 0,
- final: 0,
- ret: false,
- },
- {
- initial: 1,
- final: 2,
- ret: true,
- },
- {
- initial: 2,
- final: 3,
- ret: true,
- },
- } {
- val := test.initial
- if got, want := IncUnlessZeroInt32(&val), test.ret; got != want {
- t.Errorf("For initial value of %d: incorrect return value: got %v, wanted %v", test.initial, got, want)
- }
- if got, want := val, test.final; got != want {
- t.Errorf("For initial value of %d: incorrect final value: got %d, wanted %d", test.initial, got, want)
- }
- }
-}
-
-func TestDecUnlessOneInt32(t *testing.T) {
- for _, test := range []struct {
- initial int32
- final int32
- ret bool
- }{
- {
- initial: 0,
- final: -1,
- ret: true,
- },
- {
- initial: 1,
- final: 1,
- ret: false,
- },
- {
- initial: 2,
- final: 1,
- ret: true,
- },
- } {
- val := test.initial
- if got, want := DecUnlessOneInt32(&val), test.ret; got != want {
- t.Errorf("For initial value of %d: incorrect return value: got %v, wanted %v", test.initial, got, want)
- }
- if got, want := val, test.final; got != want {
- t.Errorf("For initial value of %d: incorrect final value: got %d, wanted %d", test.initial, got, want)
- }
- }
-}
diff --git a/pkg/sentry/mm/address_space.go b/pkg/sentry/mm/address_space.go
index e58a63deb..94d39af60 100644
--- a/pkg/sentry/mm/address_space.go
+++ b/pkg/sentry/mm/address_space.go
@@ -18,7 +18,6 @@ import (
"fmt"
"sync/atomic"
- "gvisor.dev/gvisor/pkg/atomicbitops"
"gvisor.dev/gvisor/pkg/sentry/platform"
"gvisor.dev/gvisor/pkg/usermem"
)
@@ -42,8 +41,15 @@ func (mm *MemoryManager) AddressSpace() platform.AddressSpace {
func (mm *MemoryManager) Activate() error {
// Fast path: the MemoryManager already has an active
// platform.AddressSpace, and we just need to indicate that we need it too.
- if atomicbitops.IncUnlessZeroInt32(&mm.active) {
- return nil
+ for {
+ active := atomic.LoadInt32(&mm.active)
+ if active == 0 {
+ // Fall back to the slow path.
+ break
+ }
+ if atomic.CompareAndSwapInt32(&mm.active, active, active+1) {
+ return nil
+ }
}
for {
@@ -118,8 +124,15 @@ func (mm *MemoryManager) Activate() error {
func (mm *MemoryManager) Deactivate() {
// Fast path: this is not the last goroutine to deactivate the
// MemoryManager.
- if atomicbitops.DecUnlessOneInt32(&mm.active) {
- return
+ for {
+ active := atomic.LoadInt32(&mm.active)
+ if active == 1 {
+ // Fall back to the slow path.
+ break
+ }
+ if atomic.CompareAndSwapInt32(&mm.active, active, active-1) {
+ return
+ }
}
mm.activeMu.Lock()
diff --git a/pkg/sentry/mm/lifecycle.go b/pkg/sentry/mm/lifecycle.go
index 47b8fbf43..3c263ebaa 100644
--- a/pkg/sentry/mm/lifecycle.go
+++ b/pkg/sentry/mm/lifecycle.go
@@ -18,7 +18,6 @@ import (
"fmt"
"sync/atomic"
- "gvisor.dev/gvisor/pkg/atomicbitops"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/limits"
@@ -229,7 +228,15 @@ func (mm *MemoryManager) Fork(ctx context.Context) (*MemoryManager, error) {
// IncUsers increments mm's user count and returns true. If the user count is
// already 0, IncUsers does nothing and returns false.
func (mm *MemoryManager) IncUsers() bool {
- return atomicbitops.IncUnlessZeroInt32(&mm.users)
+ for {
+ users := atomic.LoadInt32(&mm.users)
+ if users == 0 {
+ return false
+ }
+ if atomic.CompareAndSwapInt32(&mm.users, users, users+1) {
+ return true
+ }
+ }
}
// DecUsers decrements mm's user count. If the user count reaches 0, all
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 10:33:18 +0000