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runtime: tricky replacements of g in proc.go

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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>
This commit is contained in:
Michael Pratt 2022-07-20 13:31:10 -04:00
parent 4400238ec8
commit 4509e951ec
1 changed files with 17 additions and 18 deletions
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35
src/runtime/proc.go
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@ -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.