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runtime: remove mcache field from m

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Having an mcache field in both m and p is confusing, so remove it from m.
Always use mcache field from p. Use new variable mcache0 during bootstrap.

Change-Id: If2cba9f8bb131d911d512b61fd883a86cf62cc98
Reviewed-on: https://go-review.googlesource.com/c/go/+/205239
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Ian Lance Taylor 2019-11-04 14:25:22 -08:00
parent 7802b55176
commit 3093959ee1
7 changed files with 54 additions and 43 deletions
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29
src/runtime/proc.go
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@ -82,6 +82,7 @@ var modinfo string
var (
m0 m
g0 g
mcache0 *mcache
raceprocctx0 uintptr
)
@ -2957,7 +2958,6 @@ func reentersyscall(pc, sp uintptr) {
_g_.m.syscalltick = _g_.m.p.ptr().syscalltick
_g_.sysblocktraced = true
_g_.m.mcache = nil
pp := _g_.m.p.ptr()
pp.m = 0
_g_.m.oldp.set(pp)
@ -3083,9 +3083,6 @@ func exitsyscall() {
oldp := _g_.m.oldp.ptr()
_g_.m.oldp = 0
if exitsyscallfast(oldp) {
if _g_.m.mcache == nil {
throw("lost mcache")
}
if trace.enabled {
if oldp != _g_.m.p.ptr() || _g_.m.syscalltick != _g_.m.p.ptr().syscalltick {
systemstack(traceGoStart)
@ -3136,10 +3133,6 @@ func exitsyscall() {
// Call the scheduler.
mcall(exitsyscall0)
if _g_.m.mcache == nil {
throw("lost mcache")
}
// Scheduler returned, so we're allowed to run now.
// Delete the syscallsp information that we left for
// the garbage collector during the system call.
@ -4033,10 +4026,12 @@ func (pp *p) init(id int32) {
pp.wbBuf.reset()
if pp.mcache == nil {
if id == 0 {
if getg().m.mcache == nil {
if mcache0 == nil {
throw("missing mcache?")
}
pp.mcache = getg().m.mcache // bootstrap
// Use the bootstrap mcache0. Only one P will get
// mcache0: the one with ID 0.
pp.mcache = mcache0
} else {
pp.mcache = allocmcache()
}
@ -4216,7 +4211,6 @@ func procresize(nprocs int32) *p {
_g_.m.p.ptr().m = 0
}
_g_.m.p = 0
_g_.m.mcache = nil
p := allp[0]
p.m = 0
p.status = _Pidle
@ -4226,6 +4220,9 @@ func procresize(nprocs int32) *p {
}
}
// g.m.p is now set, so we no longer need mcache0 for bootstrapping.
mcache0 = nil
// release resources from unused P's
for i := nprocs; i < old; i++ {
p := allp[i]
@ -4291,7 +4288,7 @@ func acquirep(_p_ *p) {
func wirep(_p_ *p) {
_g_ := getg()
if _g_.m.p != 0 || _g_.m.mcache != nil {
if _g_.m.p != 0 {
throw("wirep: already in go")
}
if _p_.m != 0 || _p_.status != _Pidle {
@ -4302,7 +4299,6 @@ func wirep(_p_ *p) {
print("wirep: p->m=", _p_.m, "(", id, ") p->status=", _p_.status, "\n")
throw("wirep: invalid p state")
}
_g_.m.mcache = _p_.mcache
_g_.m.p.set(_p_)
_p_.m.set(_g_.m)
_p_.status = _Prunning
@ -4312,19 +4308,18 @@ func wirep(_p_ *p) {
func releasep() *p {
_g_ := getg()
if _g_.m.p == 0 || _g_.m.mcache == nil {
if _g_.m.p == 0 {
throw("releasep: invalid arg")
}
_p_ := _g_.m.p.ptr()
if _p_.m.ptr() != _g_.m || _p_.mcache != _g_.m.mcache || _p_.status != _Prunning {
print("releasep: m=", _g_.m, " m->p=", _g_.m.p.ptr(), " p->m=", hex(_p_.m), " m->mcache=", _g_.m.mcache, " p->mcache=", _p_.mcache, " p->status=", _p_.status, "\n")
if _p_.m.ptr() != _g_.m || _p_.status != _Prunning {
print("releasep: m=", _g_.m, " m->p=", _g_.m.p.ptr(), " p->m=", hex(_p_.m), " p->status=", _p_.status, "\n")
throw("releasep: invalid p state")
}
if trace.enabled {
traceProcStop(_g_.m.p.ptr())
}
_g_.m.p = 0
_g_.m.mcache = nil
_p_.m = 0
_p_.status = _Pidle
return _p_