x/playground: strict-time.patch does not apply conflict-free on Go 1.11.x

[dmitshur]

Running make test with Dockerfile updated to use Go 1.11.x fails because strict-time.patch no longer applies conflict-free.

With Go 1.10.3 (the current version in Dockerfile), we had:

Step 19/63 : RUN patch /usr/local/go/src/runtime/rt0_nacl_amd64p32.s /usr/local/playground/enable-fake-time.patch
 ---> Running in 07d052f922fd
patching file /usr/local/go/src/runtime/rt0_nacl_amd64p32.s
Removing intermediate container 07d052f922fd
 ---> 0ffdf4601200
Step 20/63 : RUN patch -p1 -d /usr/local/go </usr/local/playground/strict-time.patch
 ---> Running in 0a1d34894b7b
patching file src/runtime/os_nacl.go
Hunk #1 succeeded at 293 (offset 4 lines).
patching file src/runtime/sys_nacl_amd64p32.s

With Go 1.11.1, it currently is:

Step 19/63 : RUN patch /usr/local/go/src/runtime/rt0_nacl_amd64p32.s /usr/local/playground/enable-fake-time.patch
 ---> Running in 7fc26dbe59d4
patching file /usr/local/go/src/runtime/rt0_nacl_amd64p32.s
Removing intermediate container 7fc26dbe59d4
 ---> cd5ceaf9e81a
Step 20/63 : RUN patch -p1 -d /usr/local/go </usr/local/playground/strict-time.patch
 ---> Running in d56a00405c2d
patching file src/runtime/os_nacl.go
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file src/runtime/os_nacl.go.rej
patching file src/runtime/sys_nacl_amd64p32.s
Reversed (or previously applied) patch detected!  Assume -R? [n] 
Apply anyway? [n] 
Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file src/runtime/sys_nacl_amd64p32.s.rej
The command '/bin/sh -c patch -p1 -d /usr/local/go </usr/local/playground/strict-time.patch' returned a non-zero code: 1
Makefile:8: recipe for target 'docker' failed
make: *** [docker] Error 1

Resolving this is a prerequisite for updating the Go playground to Go 1.11.x.

CL 131435 and CL 140097 are related to this (and can't be merged without resolving this issue).

This issue is for tracking purposes. /cc @katiehockman @andybons @bradfitz

[gopherbot]

Change https://golang.org/cl/140097 mentions this issue: playground: use Go 1.11.1

[dmitshur]

Diff of applying the two .patches to Go 1.10.3 (mostly for my reference):

diff --git a/src/runtime/os_nacl.go b/src/runtime/os_nacl.go
index 6830da4c4f..1754bd875d 100644
--- a/src/runtime/os_nacl.go
+++ b/src/runtime/os_nacl.go
@@ -293,6 +293,15 @@ type gsignalStack struct{}
 
 var writelock uint32 // test-and-set spin lock for write
 
+// lastfaketime stores the last faketime value written to fd 1 or 2.
+var lastfaketime int64
+
+// lastfaketimefd stores the fd to which lastfaketime was written.
+//
+// Subsequent writes to the same fd may use the same timestamp,
+// but the timestamp must increase if the fd changes.
+var lastfaketimefd int32
+
 /*
 An attempt at IRT. Doesn't work. See end of sys_nacl_amd64.s.
 
diff --git a/src/runtime/rt0_nacl_amd64p32.s b/src/runtime/rt0_nacl_amd64p32.s
index 54e4b1de89..6ad8bea6c7 100644
--- a/src/runtime/rt0_nacl_amd64p32.s
+++ b/src/runtime/rt0_nacl_amd64p32.s
@@ -25,6 +25,6 @@ TEXT _rt0_amd64p32_nacl(SB),NOSPLIT,$16
 
 TEXT main(SB),NOSPLIT,$0
 	// Uncomment for fake time like on Go Playground.
-	//MOVQ	$1257894000000000000, AX
-	//MOVQ	AX, runtime·faketime(SB)
+	MOVQ	$1257894000000000000, AX
+	MOVQ	AX, runtime·faketime(SB)
 	JMP	runtime·rt0_go(SB)
diff --git a/src/runtime/sys_nacl_amd64p32.s b/src/runtime/sys_nacl_amd64p32.s
index ff4c2e7bb5..4c4d509576 100644
--- a/src/runtime/sys_nacl_amd64p32.s
+++ b/src/runtime/sys_nacl_amd64p32.s
@@ -89,6 +89,22 @@ playback:
 	CMPL BX, $0
 	JNE playback
 
+	MOVQ runtime·lastfaketime(SB), CX
+	MOVL runtime·lastfaketimefd(SB), BX
+	CMPL DI, BX
+	JE samefd
+
+	// If the current fd doesn't match the fd of the previous write,
+	// ensure that the timestamp is strictly greater. That way, we can
+	// recover the original order even if we read the fds separately.
+	INCQ CX
+	MOVL DI, runtime·lastfaketimefd(SB)
+
+samefd:
+	CMPQ AX, CX
+	CMOVQLT CX, AX
+	MOVQ AX, runtime·lastfaketime(SB)
+
 	// Playback header: 0 0 P B <8-byte time> <4-byte data length>
 	MOVL $(('B'<<24) | ('P'<<16)), 0(SP)
 	BSWAPQ AX

[dmitshur]

It looks like strict-time.patch isn't applying because it has already been applied to the Go tree in Go 1.11 in CL 105235.

If there's nothing unexpected, I expect the fix is as simple as removing strict-time.patch, it's no longer needed to be cherry-picked as of Go 1.11.

[bradfitz]

Yup, looks like it. Only enable-fake-time.patch is needed.

[dmitshur]

This issue has been resolved via CL 140097, and play.golang.org is running with Go 1.11.1 now:

https://play.golang.org/p/Ztyu2FJaajl