Rename procid package to hosttid.

"procid" implies "process ID", "processor (CPU?) ID", or "`runtime.p.id`". It
is none of these things. Instead, `procid.Current()` returns the caller's host
thread ID; almost every caller relies on this property. Rename the package
accordingly.

Nit: Replace "system thread identifier" with "host thread ID". "System" is
needlessly vague in a setting where many callers will also have an unrelated
application thread ID, and "identifier" is a guess at what is abbreviated by
"thread ID" - but cf. gettid(2), "NAME: gettid - get thread identification".
PiperOrigin-RevId: 507034135

pkg/hosttid/BUILD

@@ -4,37 +4,37 @@ load("//tools/nogo:defs.bzl", "nogo_facts")
 package(licenses = ["notice"])
 
 nogo_facts(
-    name = "procid_impl",
-    srcs = ["procid.go"],
-    output = "procid_impl.s",
+    name = "hosttid_impl",
+    srcs = ["hosttid.go"],
+    output = "hosttid_impl.s",
     template = select_arch(
-        amd64 = "procid_amd64.s",
-        arm64 = "procid_arm64.s",
+        amd64 = "hosttid_amd64.s",
+        arm64 = "hosttid_arm64.s",
     ),
 )
 
 arch_genrule(
-    name = "procid_impl_arch",
-    src = ":procid_impl",
-    template = "procid_impl_%s.s",
+    name = "hosttid_impl_arch",
+    src = ":hosttid_impl",
+    template = "hosttid_impl_%s.s",
 )
 
 go_library(
-    name = "procid",
+    name = "hosttid",
     srcs = [
-        "procid.go",
-        ":procid_impl_arch",
+        "hosttid.go",
+        ":hosttid_impl_arch",
     ],
     visibility = ["//visibility:public"],
 )
 
 go_test(
-    name = "procid_test",
+    name = "hosttid_test",
     size = "small",
     srcs = [
-        "procid_test.go",
+        "hosttid_test.go",
     ],
-    library = ":procid",
+    library = ":hosttid",
     deps = [
         "//pkg/sync",
         "@org_golang_x_sys//unix:go_default_library",
@@ -42,13 +42,13 @@ go_test(
 )
 
 go_test(
-    name = "procid_net_test",
+    name = "hosttid_net_test",
     size = "small",
     srcs = [
-        "procid_net_test.go",
-        "procid_test.go",
+        "hosttid_net_test.go",
+        "hosttid_test.go",
     ],
-    library = ":procid",
+    library = ":hosttid",
     deps = [
         "//pkg/sync",
         "@org_golang_x_sys//unix:go_default_library",

pkg/hosttid/hosttid.go

@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package procid provides a way to get the current system thread identifier.
-package procid
+// Package hosttid provides the Current function.
+package hosttid
 
 import (
 	"runtime"
@@ -22,7 +22,9 @@ import (
 // Dummy references for facts.
 const _ = runtime.Compiler
 
-// Current returns the current system thread identifier.
+// Current returns the caller's host thread ID. Unless runtime.LockOSThread()
+// is in effect, this function is inherently racy since the Go runtime may
+// migrate the calling goroutine to another thread at any time.
 //
-// Precondition: This should only be called with the runtime OS thread locked.
+// Current is equivalent to unix.Gettid(), but faster.
 func Current() uint64

pkg/hosttid/hosttid_net_test.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package procid
+package hosttid
 
 // This file is just to force the inclusion of the "net" package, which will
 // make the test binary a cgo one.

pkg/hosttid/hosttid_test.go

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package procid
+package hosttid
 
 import (
 	"os"

pkg/sentry/platform/kvm/BUILD

@@ -92,9 +92,9 @@ go_library(
         "//pkg/context",
         "//pkg/cpuid",
         "//pkg/hostarch",
+        "//pkg/hosttid",
         "//pkg/log",
         "//pkg/metric",
-        "//pkg/procid",
         "//pkg/ring0",
         "//pkg/ring0/pagetables",
         "//pkg/seccomp",

pkg/sentry/platform/kvm/machine.go

@@ -25,9 +25,9 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/atomicbitops"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/hosttid"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/metric"
-	"gvisor.dev/gvisor/pkg/procid"
 	"gvisor.dev/gvisor/pkg/ring0"
 	"gvisor.dev/gvisor/pkg/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/seccomp"
@@ -447,7 +447,7 @@ func (m *machine) Destroy() {
 func (m *machine) Get() *vCPU {
 	m.mu.RLock()
 	runtime.LockOSThread()
-	tid := procid.Current()
+	tid := hosttid.Current()
 
 	// Check for an exact match.
 	if c := m.vCPUsByTID[tid]; c != nil {
@@ -467,7 +467,7 @@ func (m *machine) Get() *vCPU {
 	runtime.UnlockOSThread()
 	m.mu.Lock()
 	runtime.LockOSThread()
-	tid = procid.Current()
+	tid = hosttid.Current()
 
 	// Recheck for an exact match.
 	if c := m.vCPUsByTID[tid]; c != nil {

pkg/sentry/platform/ptrace/BUILD

@@ -27,8 +27,8 @@ go_library(
         "//pkg/context",
         "//pkg/cpuid",
         "//pkg/hostarch",
+        "//pkg/hosttid",
         "//pkg/log",
-        "//pkg/procid",
         "//pkg/safecopy",
         "//pkg/seccomp",
         "//pkg/sentry/arch",

pkg/sentry/platform/ptrace/subprocess.go

@@ -22,8 +22,8 @@ import (
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/hostarch"
+	"gvisor.dev/gvisor/pkg/hosttid"
 	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/procid"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
@@ -518,7 +518,7 @@ func (s *subprocess) switchToApp(c *context, ac *arch.Context64) bool {
 	fpState := ac.FloatingPointData()
 
 	// Grab our thread from the pool.
-	currentTID := int32(procid.Current())
+	currentTID := int32(hosttid.Current())
 	t := s.sysemuThreads.lookupOrCreate(currentTID, s.newThread)
 
 	// Reset necessary registers.
@@ -627,7 +627,7 @@ func (s *subprocess) syscall(sysno uintptr, args ...arch.SyscallArgument) (uintp
 	// Grab a thread.
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
-	currentTID := int32(procid.Current())
+	currentTID := int32(hosttid.Current())
 	t := s.syscallThreads.lookupOrCreate(currentTID, s.newThread)
 
 	return t.syscallIgnoreInterrupt(&t.initRegs, sysno, args...)

pkg/sentry/platform/ptrace/subprocess_linux.go

@@ -22,8 +22,8 @@ import (
 
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/hosttid"
 	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/procid"
 	"gvisor.dev/gvisor/pkg/seccomp"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 )
@@ -210,7 +210,7 @@ func forkStub(flags uintptr, instrs []linux.BPFInstruction) (*thread, error) {
 func (s *subprocess) createStub() (*thread, error) {
 	// There's no need to lock the runtime thread here, as this can only be
 	// called from a context that is already locked.
-	currentTID := int32(procid.Current())
+	currentTID := int32(hosttid.Current())
 	t := s.syscallThreads.lookupOrCreate(currentTID, s.newThread)
 
 	// Pass the expected PPID to the child via R15.