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runtime: name nil semaphore of pollDesc

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Use explicit name pdNil for nil semaphore of a pollDesc to make it self-explanatory like pdReady and pdWait.

Change-Id: Ibfb246e14419d366edadbccac4d3717f0c135cb0
Reviewed-on: https://go-review.googlesource.com/c/go/+/424923
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
This commit is contained in:
Andy Pan 2022-08-19 18:45:51 +08:00 committed by Gopher Robot
parent 723a27994d
commit 556c978400
1 changed files with 21 additions and 20 deletions
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41
src/runtime/netpoll.go
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@ -50,16 +50,17 @@ const (
// goroutines respectively. The semaphore can be in the following states:
//
// pdReady - io readiness notification is pending;
// a goroutine consumes the notification by changing the state to nil.
// a goroutine consumes the notification by changing the state to pdNil.
// pdWait - a goroutine prepares to park on the semaphore, but not yet parked;
// the goroutine commits to park by changing the state to G pointer,
// or, alternatively, concurrent io notification changes the state to pdReady,
// or, alternatively, concurrent timeout/close changes the state to nil.
// or, alternatively, concurrent timeout/close changes the state to pdNil.
// G pointer - the goroutine is blocked on the semaphore;
// io notification or timeout/close changes the state to pdReady or nil respectively
// io notification or timeout/close changes the state to pdReady or pdNil respectively
// and unparks the goroutine.
// nil - none of the above.
// pdNil - none of the above.
const (
pdNil uintptr = 0
pdReady uintptr = 1
pdWait uintptr = 2
)
@ -93,8 +94,8 @@ type pollDesc struct {
// rg, wg are accessed atomically and hold g pointers.
// (Using atomic.Uintptr here is similar to using guintptr elsewhere.)
rg atomic.Uintptr // pdReady, pdWait, G waiting for read or nil
wg atomic.Uintptr // pdReady, pdWait, G waiting for write or nil
rg atomic.Uintptr // pdReady, pdWait, G waiting for read or pdNil
wg atomic.Uintptr // pdReady, pdWait, G waiting for write or pdNil
lock mutex // protects the following fields
closing bool
@ -217,21 +218,21 @@ func poll_runtime_pollOpen(fd uintptr) (*pollDesc, int) {
pd := pollcache.alloc()
lock(&pd.lock)
wg := pd.wg.Load()
if wg != 0 && wg != pdReady {
if wg != pdNil && wg != pdReady {
throw("runtime: blocked write on free polldesc")
}
rg := pd.rg.Load()
if rg != 0 && rg != pdReady {
if rg != pdNil && rg != pdReady {
throw("runtime: blocked read on free polldesc")
}
pd.fd = fd
pd.closing = false
pd.setEventErr(false)
pd.rseq++
pd.rg.Store(0)
pd.rg.Store(pdNil)
pd.rd = 0
pd.wseq++
pd.wg.Store(0)
pd.wg.Store(pdNil)
pd.wd = 0
pd.self = pd
pd.publishInfo()
@ -251,11 +252,11 @@ func poll_runtime_pollClose(pd *pollDesc) {
throw("runtime: close polldesc w/o unblock")
}
wg := pd.wg.Load()
if wg != 0 && wg != pdReady {
if wg != pdNil && wg != pdReady {
throw("runtime: blocked write on closing polldesc")
}
rg := pd.rg.Load()
if rg != 0 && rg != pdReady {
if rg != pdNil && rg != pdReady {
throw("runtime: blocked read on closing polldesc")
}
netpollclose(pd.fd)
@ -280,9 +281,9 @@ func poll_runtime_pollReset(pd *pollDesc, mode int) int {
return errcode
}
if mode == 'r' {
pd.rg.Store(0)
pd.rg.Store(pdNil)
} else if mode == 'w' {
pd.wg.Store(0)
pd.wg.Store(pdNil)
}
return pollNoError
}
@ -505,16 +506,16 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
// set the gpp semaphore to pdWait
for {
// Consume notification if already ready.
if gpp.CompareAndSwap(pdReady, 0) {
if gpp.CompareAndSwap(pdReady, pdNil) {
return true
}
if gpp.CompareAndSwap(0, pdWait) {
if gpp.CompareAndSwap(pdNil, pdWait) {
break
}
// Double check that this isn't corrupt; otherwise we'd loop
// forever.
if v := gpp.Load(); v != pdReady && v != 0 {
if v := gpp.Load(); v != pdReady && v != pdNil {
throw("runtime: double wait")
}
}
@ -526,7 +527,7 @@ func netpollblock(pd *pollDesc, mode int32, waitio bool) bool {
gopark(netpollblockcommit, unsafe.Pointer(gpp), waitReasonIOWait, traceEvGoBlockNet, 5)
}
// be careful to not lose concurrent pdReady notification
old := gpp.Swap(0)
old := gpp.Swap(pdNil)
if old > pdWait {
throw("runtime: corrupted polldesc")
}
@ -544,7 +545,7 @@ func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g {
if old == pdReady {
return nil
}
if old == 0 && !ioready {
if old == pdNil && !ioready {
// Only set pdReady for ioready. runtime_pollWait
// will check for timeout/cancel before waiting.
return nil
@ -555,7 +556,7 @@ func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g {
}
if gpp.CompareAndSwap(old, new) {
if old == pdWait {
old = 0
old = pdNil
}
return (*g)(unsafe.Pointer(old))
}