syscall: document LockOSThread with GNU/Linux SysProcAttr.Ptrace

Fixes #28315

Change-Id: Ie02c72d02ad2f66c9cdbbba579a304641f327672
Reviewed-on: https://go-review.googlesource.com/c/155138
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go
index 7ae3177fdc087859dc4834fe064a02095885e9a1..6c761f85c441882e0b5d2adc4c947c834fe209d8 100644 (file)
--- a/src/syscall/exec_linux.go
+++ b/src/syscall/exec_linux.go
@@ -20,9 +20,12 @@ type SysProcIDMap struct {
 }
 
 type SysProcAttr struct {
-       Chroot       string         // Chroot.
-       Credential   *Credential    // Credential.
-       Ptrace       bool           // Enable tracing.
+       Chroot     string      // Chroot.
+       Credential *Credential // Credential.
+       // Ptrace tells the child to call ptrace(PTRACE_TRACEME).
+       // Call runtime.LockOSThread before starting a process with this set,
+       // and don't call UnlockOSThread until done with PtraceSyscall calls.
+       Ptrace       bool
        Setsid       bool           // Create session.
        Setpgid      bool           // Set process group ID to Pgid, or, if Pgid == 0, to new pid.
        Setctty      bool           // Set controlling terminal to fd Ctty (only meaningful if Setsid is set)