Revert "os: make FindProcess use pidfd on Linux"

This reverts CL 542699.

Reason for revert: Some applications assume FindProcess does not return
errors.

For #62654.
Fixes #65866.

Change-Id: Ic185a6253c8e508b08150b618c39a9905f6cdd60
Reviewed-on: https://go-review.googlesource.com/c/go/+/566476
Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Pratt <mpratt@google.com>

diff --git a/doc/godebug.md b/doc/godebug.md
index 9dbbab284dbef0235d15611c5d1ffc77fd24c338..a7619c9a3da48a7fa289bf5a9508ad6e2987eafe 100644 (file)
--- a/doc/godebug.md
+++ b/doc/godebug.md
@@ -126,11 +126,6 @@ for example,
 see the [runtime documentation](/pkg/runtime#hdr-Environment_Variables)
 and the [go command documentation](/cmd/go#hdr-Build_and_test_caching).
 
-### Go 1.23
-
-Go 1.23 enabled Linux pidfd support for process lookup. This feature can be
-disabled by using the [`osfinderr` setting](/pkg/os#FindProcess).
-
 ### Go 1.22
 
 Go 1.22 adds a configurable limit to control the maximum acceptable RSA key size

diff --git a/src/internal/godebugs/table.go b/src/internal/godebugs/table.go
index 4ac306b323dfeb005e818bd7e2a462a72f6dd873..a0a067296686419e57545cf41d3581b6163c640d 100644 (file)
--- a/src/internal/godebugs/table.go
+++ b/src/internal/godebugs/table.go
@@ -42,7 +42,6 @@ var All = []Info{
        {Name: "multipartmaxparts", Package: "mime/multipart"},
        {Name: "multipathtcp", Package: "net"},
        {Name: "netdns", Package: "net", Opaque: true},
-       {Name: "osfinderr", Package: "os"},
        {Name: "panicnil", Package: "runtime", Changed: 21, Old: "1"},
        {Name: "randautoseed", Package: "math/rand"},
        {Name: "tarinsecurepath", Package: "archive/tar"},

diff --git a/src/os/exec.go b/src/os/exec.go
index 7ef1fee595b379083390df4a95811d912b6a25f6..42e8a399a9878c15cfa6e5f38bf21ede6a7d7c1f 100644 (file)
--- a/src/os/exec.go
+++ b/src/os/exec.go
@@ -86,17 +86,10 @@ func Getppid() int { return syscall.Getppid() }
 // The Process it returns can be used to obtain information
 // about the underlying operating system process.
 //
-// On Unix systems other than Linux, FindProcess always succeeds and returns a Process
+// On Unix systems, FindProcess always succeeds and returns a Process
 // for the given pid, regardless of whether the process exists. To test whether
 // the process actually exists, see whether p.Signal(syscall.Signal(0)) reports
 // an error.
-//
-// On Linux, FindProcess may either return ErrProcessGone for a non-existing
-// process (thus eliminating the need to use a signal to check if the process
-// exists), or work the same way as for other Unix systems, described above,
-// depending on the kernel version used and the system configuration. The old
-// behavior (of always succeeding) can be enforced by using GODEBUG setting
-// osfinderr=0.
 func FindProcess(pid int) (*Process, error) {
        return findProcess(pid)
 }

diff --git a/src/os/exec_unix.go b/src/os/exec_unix.go
index 21d03da48ecf397e9e0939aa45e24aa6e8df0e3b..2c66a8be20325022a4b529445e24be0c49dfd240 100644 (file)
--- a/src/os/exec_unix.go
+++ b/src/os/exec_unix.go
@@ -106,14 +106,8 @@ func (p *Process) release() error {
 }
 
 func findProcess(pid int) (p *Process, err error) {
-       h, err := pidfdFind(pid)
-       if err == ErrProcessDone {
-               return nil, err
-       }
-       // Ignore all other errors from pidfdFind,
-       // as the callers do not expect them, and
-       // we can use pid anyway.
-       return newProcess(pid, h), nil
+       // NOOP for unix.
+       return newProcess(pid, unsetHandle), nil
 }
 
 func (p *ProcessState) userTime() time.Duration {

diff --git a/src/os/pidfd_linux.go b/src/os/pidfd_linux.go
index cc67dfa05f662cfcb1b541277600f243c5f1fae0..d6e1d53eee8e26e0624ad0f3e868af9d38ee37bb 100644 (file)
--- a/src/os/pidfd_linux.go
+++ b/src/os/pidfd_linux.go
@@ -14,7 +14,6 @@
 package os
 
 import (
-       "internal/godebug"
        "internal/syscall/unix"
        "sync"
        "syscall"
@@ -50,25 +49,6 @@ func getPidfd(sysAttr *syscall.SysProcAttr) uintptr {
        return uintptr(*sysAttr.PidFD)
 }
 
-var osfinderr = godebug.New("osfinderr")
-
-func pidfdFind(pid int) (uintptr, error) {
-       if !pidfdWorks() {
-               return unsetHandle, syscall.ENOSYS
-       }
-       if osfinderr.Value() == "0" {
-               osfinderr.IncNonDefault()
-               return unsetHandle, syscall.ENOSYS
-
-       }
-
-       h, err := unix.PidFDOpen(pid, 0)
-       if err == nil {
-               return h, nil
-       }
-       return unsetHandle, convertESRCH(err)
-}
-
 func (p *Process) pidfdRelease() {
        // Release pidfd unconditionally.
        handle := p.handle.Swap(unsetHandle)

diff --git a/src/os/pidfd_other.go b/src/os/pidfd_other.go
index bb38c724042bc27c545dce71b241a8ec5e6e87db..1918acbec5b7658e55224cdeebb2dfb01cbb2e44 100644 (file)
--- a/src/os/pidfd_other.go
+++ b/src/os/pidfd_other.go
@@ -16,10 +16,6 @@ func getPidfd(_ *syscall.SysProcAttr) uintptr {
        return unsetHandle
 }
 
-func pidfdFind(_ int) (uintptr, error) {
-       return unsetHandle, syscall.ENOSYS
-}
-
 func (p *Process) pidfdRelease() {}
 
 func (_ *Process) pidfdWait() (*ProcessState, error) {

diff --git a/src/runtime/metrics/doc.go b/src/runtime/metrics/doc.go
index d1c2f8aa25c544b609a4a8673b41a521de7a4087..fb2f44da29c55df23e182a0e397be336594a4fb0 100644 (file)
--- a/src/runtime/metrics/doc.go
+++ b/src/runtime/metrics/doc.go
@@ -290,10 +290,6 @@ Below is the full list of supported metrics, ordered lexicographically.
                The number of non-default behaviors executed by the net package
                due to a non-default GODEBUG=multipathtcp=... setting.
 
-       /godebug/non-default-behavior/osfinderr:events
-               The number of non-default behaviors executed by the os package
-               due to a non-default GODEBUG=osfinderr=... setting.
-
        /godebug/non-default-behavior/panicnil:events
                The number of non-default behaviors executed by the runtime
                package due to a non-default GODEBUG=panicnil=... setting.