75 lines
2.0 KiB
Go
75 lines
2.0 KiB
Go
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fdnotifier
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import (
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"syscall"
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"unsafe"
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"gvisor.googlesource.com/gvisor/pkg/waiter"
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)
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// NonBlockingPoll polls the given FD in non-blocking fashion. It is used just
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// to query the FD's current state.
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func NonBlockingPoll(fd int32, mask waiter.EventMask) waiter.EventMask {
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e := struct {
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fd int32
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events int16
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revents int16
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}{
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fd: fd,
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events: int16(mask),
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}
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for {
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n, _, err := syscall.RawSyscall(syscall.SYS_POLL, uintptr(unsafe.Pointer(&e)), 1, 0)
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// Interrupted by signal, try again.
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if err == syscall.EINTR {
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continue
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}
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// If an error occur we'll conservatively say the FD is ready for
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// whatever is being checked.
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if err != 0 {
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return mask
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}
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// If no FDs were returned, it wasn't ready for anything.
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if n == 0 {
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return 0
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}
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// Otherwise we got the ready events in the revents field.
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return waiter.EventMask(e.revents)
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}
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}
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// epollWait performs a blocking wait on epfd.
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//
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// Preconditions:
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// * len(events) > 0
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func epollWait(epfd int, events []syscall.EpollEvent, msec int) (int, error) {
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if len(events) == 0 {
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panic("Empty events passed to EpollWait")
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}
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// We actually use epoll_pwait with NULL sigmask instead of epoll_wait
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// since that is what the Go >= 1.11 runtime prefers.
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r, _, e := syscall.Syscall6(syscall.SYS_EPOLL_PWAIT, uintptr(epfd), uintptr(unsafe.Pointer(&events[0])), uintptr(len(events)), uintptr(msec), 0, 0)
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if e != 0 {
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return 0, e
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}
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return int(r), nil
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}
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