runtime: rename p racectx field to raceprocctx

Both g and p had a racectx field, but they held different kinds of values.
The g field held ThreadState values while the p field held Processor values
(to use the names used in the C++ code in the compiler_rt support library).
Rename the p field to raceprocctx to reduce potential confusion.

Change-Id: Iefba0e259d240171e973054c452c3c15bf3f8f8f
Reviewed-on: https://go-review.googlesource.com/c/go/+/169960Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/proc.go

@@ -3956,12 +3956,12 @@ func procresize(nprocs int32) *p {
 				pp.mcache = allocmcache()
 			}
 		}
-		if raceenabled && pp.racectx == 0 {
+		if raceenabled && pp.raceprocctx == 0 {
 			if old == 0 && i == 0 {
-				pp.racectx = raceprocctx0
+				pp.raceprocctx = raceprocctx0
 				raceprocctx0 = 0 // bootstrap
 			} else {
-				pp.racectx = raceproccreate()
+				pp.raceprocctx = raceproccreate()
 			}
 		}
 	}
@@ -4019,8 +4019,8 @@ func procresize(nprocs int32) *p {
 		gfpurge(p)
 		traceProcFree(p)
 		if raceenabled {
-			raceprocdestroy(p.racectx)
-			p.racectx = 0
+			raceprocdestroy(p.raceprocctx)
+			p.raceprocctx = 0
 		}
 		p.gcAssistTime = 0
 		p.status = _Pdead

src/runtime/race_amd64.s

@@ -398,7 +398,7 @@ TEXT	runtime·racecallbackthunk(SB), NOSPLIT, $56-8
 	MOVQ	g(RARG0), RARG0
 	MOVQ	g_m(RARG0), RARG0
 	MOVQ	m_p(RARG0), RARG0
-	MOVQ	p_racectx(RARG0), RARG0
+	MOVQ	p_raceprocctx(RARG0), RARG0
 	MOVQ	RARG0, (RARG1)
 	RET
 

src/runtime/race_ppc64le.s

@@ -455,7 +455,7 @@ TEXT	runtime·racecallbackthunk(SB), NOSPLIT, $-8
 	MOVD    0(R13)(R10*1), g
 	MOVD	g_m(g), R3
 	MOVD	m_p(R3), R3
-	MOVD	p_racectx(R3), R3
+	MOVD	p_raceprocctx(R3), R3
 	MOVD	R3, (R4)
 	MOVD	R9, g		// restore R30 ??
 	RET

src/runtime/runtime2.go

@@ -482,7 +482,7 @@ type p struct {
 	sysmontick  sysmontick // last tick observed by sysmon
 	m           muintptr   // back-link to associated m (nil if idle)
 	mcache      *mcache
-	racectx     uintptr
+	raceprocctx uintptr
 
 	deferpool    [5][]*_defer // pool of available defer structs of different sizes (see panic.go)
 	deferpoolbuf [5][32]*_defer