runtime: tricky replacements of g in proc.go

Change-Id: I36cd167ed77e123b3ba7dd4a1a8577cbc51a84d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/418588
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index e08a90113a755d6b9132e3cf0743cd165017cbb0..0b3d90c5b236dcfc7413b03a7e9fbc86a29fbecc 100644 (file)
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -143,11 +143,11 @@ var initSigmask sigset
 
 // The main goroutine.
 func main() {
-       g := getg()
+       mp := getg().m
 
        // Racectx of m0->g0 is used only as the parent of the main goroutine.
        // It must not be used for anything else.
-       g.m.g0.racectx = 0
+       mp.g0.racectx = 0
 
        // Max stack size is 1 GB on 64-bit, 250 MB on 32-bit.
        // Using decimal instead of binary GB and MB because
@@ -180,7 +180,7 @@ func main() {
        // to preserve the lock.
        lockOSThread()
 
-       if g.m != &m0 {
+       if mp != &m0 {
                throw("runtime.main not on m0")
        }
 
@@ -1468,10 +1468,9 @@ func mPark() {
 //
 //go:yeswritebarrierrec
 func mexit(osStack bool) {
-       g := getg()
-       m := g.m
+       mp := getg().m
 
-       if m == &m0 {
+       if mp == &m0 {
                // This is the main thread. Just wedge it.
                //
                // On Linux, exiting the main thread puts the process
@@ -1496,20 +1495,20 @@ func mexit(osStack bool) {
        unminit()
 
        // Free the gsignal stack.
-       if m.gsignal != nil {
-               stackfree(m.gsignal.stack)
+       if mp.gsignal != nil {
+               stackfree(mp.gsignal.stack)
                // On some platforms, when calling into VDSO (e.g. nanotime)
                // we store our g on the gsignal stack, if there is one.
                // Now the stack is freed, unlink it from the m, so we
                // won't write to it when calling VDSO code.
-               m.gsignal = nil
+               mp.gsignal = nil
        }
 
        // Remove m from allm.
        lock(&sched.lock)
        for pprev := &allm; *pprev != nil; pprev = &(*pprev).alllink {
-               if *pprev == m {
-                       *pprev = m.alllink
+               if *pprev == mp {
+                       *pprev = mp.alllink
                        goto found
                }
        }
@@ -1520,17 +1519,17 @@ found:
                //
                // If this is using an OS stack, the OS will free it
                // so there's no need for reaping.
-               atomic.Store(&m.freeWait, 1)
+               atomic.Store(&mp.freeWait, 1)
                // Put m on the free list, though it will not be reaped until
                // freeWait is 0. Note that the free list must not be linked
                // through alllink because some functions walk allm without
                // locking, so may be using alllink.
-               m.freelink = sched.freem
-               sched.freem = m
+               mp.freelink = sched.freem
+               sched.freem = mp
        }
        unlock(&sched.lock)
 
-       atomic.Xadd64(&ncgocall, int64(m.ncgocall))
+       atomic.Xadd64(&ncgocall, int64(mp.ncgocall))
 
        // Release the P.
        handoffp(releasep())
@@ -1547,14 +1546,14 @@ found:
        if GOOS == "darwin" || GOOS == "ios" {
                // Make sure pendingPreemptSignals is correct when an M exits.
                // For #41702.
-               if atomic.Load(&m.signalPending) != 0 {
+               if atomic.Load(&mp.signalPending) != 0 {
                        atomic.Xadd(&pendingPreemptSignals, -1)
                }
        }
 
        // Destroy all allocated resources. After this is called, we may no
        // longer take any locks.
-       mdestroy(m)
+       mdestroy(mp)
 
        if osStack {
                // Return from mstart and let the system thread
@@ -1566,7 +1565,7 @@ found:
        // return to. Exit the thread directly. exitThread will clear
        // m.freeWait when it's done with the stack and the m can be
        // reaped.
-       exitThread(&m.freeWait)
+       exitThread(&mp.freeWait)
 }
 
 // forEachP calls fn(p) for every P p when p reaches a GC safe point.