diff options
Diffstat (limited to 'libgo/go/runtime/netpoll.go')
| -rw-r--r-- | libgo/go/runtime/netpoll.go | 452 |
1 files changed, 452 insertions, 0 deletions
diff --git a/libgo/go/runtime/netpoll.go b/libgo/go/runtime/netpoll.go new file mode 100644 index 0000000..729b597 --- /dev/null +++ b/libgo/go/runtime/netpoll.go @@ -0,0 +1,452 @@ +// Copyright 2013 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows + +package runtime + +import ( + "runtime/internal/atomic" + "unsafe" +) + +// Export temporarily for gccgo's C code to call: +//go:linkname netpoll runtime.netpoll + +// Integrated network poller (platform-independent part). +// A particular implementation (epoll/kqueue) must define the following functions: +// func netpollinit() // to initialize the poller +// func netpollopen(fd uintptr, pd *pollDesc) int32 // to arm edge-triggered notifications +// and associate fd with pd. +// An implementation must call the following function to denote that the pd is ready. +// func netpollready(gpp **g, pd *pollDesc, mode int32) + +// pollDesc contains 2 binary semaphores, rg and wg, to park reader and writer +// 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. +// 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 READY, +// or, alternatively, concurrent timeout/close changes the state to nil. +// G pointer - the goroutine is blocked on the semaphore; +// io notification or timeout/close changes the state to READY or nil respectively +// and unparks the goroutine. +// nil - nothing of the above. +const ( + pdReady uintptr = 1 + pdWait uintptr = 2 +) + +const pollBlockSize = 4 * 1024 + +// Network poller descriptor. +type pollDesc struct { + link *pollDesc // in pollcache, protected by pollcache.lock + + // The lock protects pollOpen, pollSetDeadline, pollUnblock and deadlineimpl operations. + // This fully covers seq, rt and wt variables. fd is constant throughout the PollDesc lifetime. + // pollReset, pollWait, pollWaitCanceled and runtime·netpollready (IO readiness notification) + // proceed w/o taking the lock. So closing, rg, rd, wg and wd are manipulated + // in a lock-free way by all operations. + // NOTE(dvyukov): the following code uses uintptr to store *g (rg/wg), + // that will blow up when GC starts moving objects. + lock mutex // protects the following fields + fd uintptr + closing bool + seq uintptr // protects from stale timers and ready notifications + rg uintptr // pdReady, pdWait, G waiting for read or nil + rt timer // read deadline timer (set if rt.f != nil) + rd int64 // read deadline + wg uintptr // pdReady, pdWait, G waiting for write or nil + wt timer // write deadline timer + wd int64 // write deadline + user uint32 // user settable cookie +} + +type pollCache struct { + lock mutex + first *pollDesc + // PollDesc objects must be type-stable, + // because we can get ready notification from epoll/kqueue + // after the descriptor is closed/reused. + // Stale notifications are detected using seq variable, + // seq is incremented when deadlines are changed or descriptor is reused. +} + +var ( + netpollInited uint32 + pollcache pollCache +) + +//go:linkname net_runtime_pollServerInit net.runtime_pollServerInit +func net_runtime_pollServerInit() { + netpollinit() + atomic.Store(&netpollInited, 1) +} + +func netpollinited() bool { + return atomic.Load(&netpollInited) != 0 +} + +//go:linkname net_runtime_pollOpen net.runtime_pollOpen +func net_runtime_pollOpen(fd uintptr) (*pollDesc, int) { + pd := pollcache.alloc() + lock(&pd.lock) + if pd.wg != 0 && pd.wg != pdReady { + throw("netpollOpen: blocked write on free descriptor") + } + if pd.rg != 0 && pd.rg != pdReady { + throw("netpollOpen: blocked read on free descriptor") + } + pd.fd = fd + pd.closing = false + pd.seq++ + pd.rg = 0 + pd.rd = 0 + pd.wg = 0 + pd.wd = 0 + unlock(&pd.lock) + + var errno int32 + errno = netpollopen(fd, pd) + return pd, int(errno) +} + +//go:linkname net_runtime_pollClose net.runtime_pollClose +func net_runtime_pollClose(pd *pollDesc) { + if !pd.closing { + throw("netpollClose: close w/o unblock") + } + if pd.wg != 0 && pd.wg != pdReady { + throw("netpollClose: blocked write on closing descriptor") + } + if pd.rg != 0 && pd.rg != pdReady { + throw("netpollClose: blocked read on closing descriptor") + } + netpollclose(pd.fd) + pollcache.free(pd) +} + +func (c *pollCache) free(pd *pollDesc) { + lock(&c.lock) + pd.link = c.first + c.first = pd + unlock(&c.lock) +} + +//go:linkname net_runtime_pollReset net.runtime_pollReset +func net_runtime_pollReset(pd *pollDesc, mode int) int { + err := netpollcheckerr(pd, int32(mode)) + if err != 0 { + return err + } + if mode == 'r' { + pd.rg = 0 + } else if mode == 'w' { + pd.wg = 0 + } + return 0 +} + +//go:linkname net_runtime_pollWait net.runtime_pollWait +func net_runtime_pollWait(pd *pollDesc, mode int) int { + err := netpollcheckerr(pd, int32(mode)) + if err != 0 { + return err + } + // As for now only Solaris uses level-triggered IO. + if GOOS == "solaris" { + netpollarm(pd, mode) + } + for !netpollblock(pd, int32(mode), false) { + err = netpollcheckerr(pd, int32(mode)) + if err != 0 { + return err + } + // Can happen if timeout has fired and unblocked us, + // but before we had a chance to run, timeout has been reset. + // Pretend it has not happened and retry. + } + return 0 +} + +//go:linkname net_runtime_pollWaitCanceled net.runtime_pollWaitCanceled +func net_runtime_pollWaitCanceled(pd *pollDesc, mode int) { + // This function is used only on windows after a failed attempt to cancel + // a pending async IO operation. Wait for ioready, ignore closing or timeouts. + for !netpollblock(pd, int32(mode), true) { + } +} + +//go:linkname net_runtime_pollSetDeadline net.runtime_pollSetDeadline +func net_runtime_pollSetDeadline(pd *pollDesc, d int64, mode int) { + lock(&pd.lock) + if pd.closing { + unlock(&pd.lock) + return + } + pd.seq++ // invalidate current timers + // Reset current timers. + if pd.rt.f != nil { + deltimer(&pd.rt) + pd.rt.f = nil + } + if pd.wt.f != nil { + deltimer(&pd.wt) + pd.wt.f = nil + } + // Setup new timers. + if d != 0 && d <= nanotime() { + d = -1 + } + if mode == 'r' || mode == 'r'+'w' { + pd.rd = d + } + if mode == 'w' || mode == 'r'+'w' { + pd.wd = d + } + if pd.rd > 0 && pd.rd == pd.wd { + pd.rt.f = netpollDeadline + pd.rt.when = pd.rd + // Copy current seq into the timer arg. + // Timer func will check the seq against current descriptor seq, + // if they differ the descriptor was reused or timers were reset. + pd.rt.arg = pd + pd.rt.seq = pd.seq + addtimer(&pd.rt) + } else { + if pd.rd > 0 { + pd.rt.f = netpollReadDeadline + pd.rt.when = pd.rd + pd.rt.arg = pd + pd.rt.seq = pd.seq + addtimer(&pd.rt) + } + if pd.wd > 0 { + pd.wt.f = netpollWriteDeadline + pd.wt.when = pd.wd + pd.wt.arg = pd + pd.wt.seq = pd.seq + addtimer(&pd.wt) + } + } + // If we set the new deadline in the past, unblock currently pending IO if any. + var rg, wg *g + atomicstorep(unsafe.Pointer(&wg), nil) // full memory barrier between stores to rd/wd and load of rg/wg in netpollunblock + if pd.rd < 0 { + rg = netpollunblock(pd, 'r', false) + } + if pd.wd < 0 { + wg = netpollunblock(pd, 'w', false) + } + unlock(&pd.lock) + if rg != nil { + goready(rg, 3) + } + if wg != nil { + goready(wg, 3) + } +} + +//go:linkname net_runtime_pollUnblock net.runtime_pollUnblock +func net_runtime_pollUnblock(pd *pollDesc) { + lock(&pd.lock) + if pd.closing { + throw("netpollUnblock: already closing") + } + pd.closing = true + pd.seq++ + var rg, wg *g + atomicstorep(unsafe.Pointer(&rg), nil) // full memory barrier between store to closing and read of rg/wg in netpollunblock + rg = netpollunblock(pd, 'r', false) + wg = netpollunblock(pd, 'w', false) + if pd.rt.f != nil { + deltimer(&pd.rt) + pd.rt.f = nil + } + if pd.wt.f != nil { + deltimer(&pd.wt) + pd.wt.f = nil + } + unlock(&pd.lock) + if rg != nil { + goready(rg, 3) + } + if wg != nil { + goready(wg, 3) + } +} + +// make pd ready, newly runnable goroutines (if any) are returned in rg/wg +// May run during STW, so write barriers are not allowed. +//go:nowritebarrier +func netpollready(gpp *guintptr, pd *pollDesc, mode int32) { + var rg, wg guintptr + if mode == 'r' || mode == 'r'+'w' { + rg.set(netpollunblock(pd, 'r', true)) + } + if mode == 'w' || mode == 'r'+'w' { + wg.set(netpollunblock(pd, 'w', true)) + } + if rg != 0 { + rg.ptr().schedlink = *gpp + *gpp = rg + } + if wg != 0 { + wg.ptr().schedlink = *gpp + *gpp = wg + } +} + +func netpollcheckerr(pd *pollDesc, mode int32) int { + if pd.closing { + return 1 // errClosing + } + if (mode == 'r' && pd.rd < 0) || (mode == 'w' && pd.wd < 0) { + return 2 // errTimeout + } + return 0 +} + +func netpollblockcommit(gp *g, gpp unsafe.Pointer) bool { + return atomic.Casuintptr((*uintptr)(gpp), pdWait, uintptr(unsafe.Pointer(gp))) +} + +// returns true if IO is ready, or false if timedout or closed +// waitio - wait only for completed IO, ignore errors +func netpollblock(pd *pollDesc, mode int32, waitio bool) bool { + gpp := &pd.rg + if mode == 'w' { + gpp = &pd.wg + } + + // set the gpp semaphore to WAIT + for { + old := *gpp + if old == pdReady { + *gpp = 0 + return true + } + if old != 0 { + throw("netpollblock: double wait") + } + if atomic.Casuintptr(gpp, 0, pdWait) { + break + } + } + + // need to recheck error states after setting gpp to WAIT + // this is necessary because runtime_pollUnblock/runtime_pollSetDeadline/deadlineimpl + // do the opposite: store to closing/rd/wd, membarrier, load of rg/wg + if waitio || netpollcheckerr(pd, mode) == 0 { + gopark(netpollblockcommit, unsafe.Pointer(gpp), "IO wait", traceEvGoBlockNet, 5) + } + // be careful to not lose concurrent READY notification + old := atomic.Xchguintptr(gpp, 0) + if old > pdWait { + throw("netpollblock: corrupted state") + } + return old == pdReady +} + +func netpollunblock(pd *pollDesc, mode int32, ioready bool) *g { + gpp := &pd.rg + if mode == 'w' { + gpp = &pd.wg + } + + for { + old := *gpp + if old == pdReady { + return nil + } + if old == 0 && !ioready { + // Only set READY for ioready. runtime_pollWait + // will check for timeout/cancel before waiting. + return nil + } + var new uintptr + if ioready { + new = pdReady + } + if atomic.Casuintptr(gpp, old, new) { + if old == pdReady || old == pdWait { + old = 0 + } + return (*g)(unsafe.Pointer(old)) + } + } +} + +func netpolldeadlineimpl(pd *pollDesc, seq uintptr, read, write bool) { + lock(&pd.lock) + // Seq arg is seq when the timer was set. + // If it's stale, ignore the timer event. + if seq != pd.seq { + // The descriptor was reused or timers were reset. + unlock(&pd.lock) + return + } + var rg *g + if read { + if pd.rd <= 0 || pd.rt.f == nil { + throw("netpolldeadlineimpl: inconsistent read deadline") + } + pd.rd = -1 + atomicstorep(unsafe.Pointer(&pd.rt.f), nil) // full memory barrier between store to rd and load of rg in netpollunblock + rg = netpollunblock(pd, 'r', false) + } + var wg *g + if write { + if pd.wd <= 0 || pd.wt.f == nil && !read { + throw("netpolldeadlineimpl: inconsistent write deadline") + } + pd.wd = -1 + atomicstorep(unsafe.Pointer(&pd.wt.f), nil) // full memory barrier between store to wd and load of wg in netpollunblock + wg = netpollunblock(pd, 'w', false) + } + unlock(&pd.lock) + if rg != nil { + goready(rg, 0) + } + if wg != nil { + goready(wg, 0) + } +} + +func netpollDeadline(arg interface{}, seq uintptr) { + netpolldeadlineimpl(arg.(*pollDesc), seq, true, true) +} + +func netpollReadDeadline(arg interface{}, seq uintptr) { + netpolldeadlineimpl(arg.(*pollDesc), seq, true, false) +} + +func netpollWriteDeadline(arg interface{}, seq uintptr) { + netpolldeadlineimpl(arg.(*pollDesc), seq, false, true) +} + +func (c *pollCache) alloc() *pollDesc { + lock(&c.lock) + if c.first == nil { + const pdSize = unsafe.Sizeof(pollDesc{}) + n := pollBlockSize / pdSize + if n == 0 { + n = 1 + } + // Must be in non-GC memory because can be referenced + // only from epoll/kqueue internals. + mem := persistentalloc(n*pdSize, 0, &memstats.other_sys) + for i := uintptr(0); i < n; i++ { + pd := (*pollDesc)(add(mem, i*pdSize)) + pd.link = c.first + c.first = pd + } + } + pd := c.first + c.first = pd.link + unlock(&c.lock) + return pd +} |