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https://github.com/golang/go
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84cfba17c2
Ian proposed an improved way of handling signals masks in Go, motivated by a problem where the Android java runtime expects certain signals to be blocked for all JVM threads. Discussion here https://groups.google.com/forum/#!topic/golang-dev/_TSCkQHJt6g Ian's text is used in the following: A Go program always needs to have the synchronous signals enabled. These are the signals for which _SigPanic is set in sigtable, namely SIGSEGV, SIGBUS, SIGFPE. A Go program that uses the os/signal package, and calls signal.Notify, needs to have at least one thread which is not blocking that signal, but it doesn't matter much which one. Unix programs do not change signal mask across execve. They inherit signal masks across fork. The shell uses this fact to some extent; for example, the job control signals (SIGTTIN, SIGTTOU, SIGTSTP) are blocked for commands run due to backquote quoting or $(). Our current position on signal masks was not thought out. We wandered into step by step, e.g., http://golang.org/cl/7323067 . This CL does the following: Introduce a new platform hook, msigsave, that saves the signal mask of the current thread to m.sigsave. Call msigsave from needm and newm. In minit grab set up the signal mask from m.sigsave and unblock the essential synchronous signals, and SIGILL, SIGTRAP, SIGPROF, SIGSTKFLT (for systems that have it). In unminit, restore the signal mask from m.sigsave. The first time that os/signal.Notify is called, start a new thread whose only purpose is to update its signal mask to make sure signals for signal.Notify are unblocked on at least one thread. The effect on Go programs will be that if they are invoked with some non-synchronous signals blocked, those signals will normally be ignored. Previously, those signals would mostly be ignored. A change in behaviour will occur for programs started with any of these signals blocked, if they receive the signal: SIGHUP, SIGINT, SIGQUIT, SIGABRT, SIGTERM. Previously those signals would always cause a crash (unless using the os/signal package); with this change, they will be ignored if the program is started with the signal blocked (and does not use the os/signal package). ./all.bash completes successfully on linux/amd64. OpenBSD is missing the implementation. Change-Id: I188098ba7eb85eae4c14861269cc466f2aa40e8c Reviewed-on: https://go-review.googlesource.com/10173 Reviewed-by: Ian Lance Taylor <iant@golang.org>
89 lines
4.4 KiB
Go
89 lines
4.4 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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type sigTabT struct {
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flags int32
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name string
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}
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var sigtable = [...]sigTabT{
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/* 0 */ {0, "SIGNONE: no trap"},
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/* 1 */ {_SigNotify + _SigKill, "SIGHUP: hangup"},
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/* 2 */ {_SigNotify + _SigKill, "SIGINT: interrupt (rubout)"},
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/* 3 */ {_SigNotify + _SigThrow, "SIGQUIT: quit (ASCII FS)"},
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/* 4 */ {_SigThrow + _SigUnblock, "SIGILL: illegal instruction (not reset when caught)"},
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/* 5 */ {_SigThrow + _SigUnblock, "SIGTRAP: trace trap (not reset when caught)"},
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/* 6 */ {_SigNotify + _SigThrow, "SIGABRT: used by abort, replace SIGIOT in the future"},
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/* 7 */ {_SigThrow, "SIGEMT: EMT instruction"},
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/* 8 */ {_SigPanic + _SigUnblock, "SIGFPE: floating point exception"},
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/* 9 */ {0, "SIGKILL: kill (cannot be caught or ignored)"},
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/* 10 */ {_SigPanic + _SigUnblock, "SIGBUS: bus error"},
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/* 11 */ {_SigPanic + _SigUnblock, "SIGSEGV: segmentation violation"},
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/* 12 */ {_SigThrow, "SIGSYS: bad argument to system call"},
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/* 13 */ {_SigNotify, "SIGPIPE: write on a pipe with no one to read it"},
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/* 14 */ {_SigNotify, "SIGALRM: alarm clock"},
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/* 15 */ {_SigNotify + _SigKill, "SIGTERM: software termination signal from kill"},
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/* 16 */ {_SigNotify, "SIGUSR1: user defined signal 1"},
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/* 17 */ {_SigNotify, "SIGUSR2: user defined signal 2"},
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/* 18 */ {_SigNotify + _SigUnblock, "SIGCHLD: child status change alias (POSIX)"},
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/* 19 */ {_SigNotify, "SIGPWR: power-fail restart"},
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/* 20 */ {_SigNotify, "SIGWINCH: window size change"},
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/* 21 */ {_SigNotify, "SIGURG: urgent socket condition"},
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/* 22 */ {_SigNotify, "SIGPOLL: pollable event occured"},
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/* 23 */ {_SigNotify + _SigDefault, "SIGSTOP: stop (cannot be caught or ignored)"},
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/* 24 */ {0, "SIGTSTP: user stop requested from tty"},
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/* 25 */ {0, "SIGCONT: stopped process has been continued"},
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/* 26 */ {_SigNotify + _SigDefault, "SIGTTIN: background tty read attempted"},
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/* 27 */ {_SigNotify + _SigDefault, "SIGTTOU: background tty write attempted"},
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/* 28 */ {_SigNotify, "SIGVTALRM: virtual timer expired"},
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/* 29 */ {_SigNotify + _SigUnblock, "SIGPROF: profiling timer expired"},
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/* 30 */ {_SigNotify, "SIGXCPU: exceeded cpu limit"},
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/* 31 */ {_SigNotify, "SIGXFSZ: exceeded file size limit"},
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/* 32 */ {_SigNotify, "SIGWAITING: reserved signal no longer used by"},
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/* 33 */ {_SigNotify, "SIGLWP: reserved signal no longer used by"},
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/* 34 */ {_SigNotify, "SIGFREEZE: special signal used by CPR"},
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/* 35 */ {_SigNotify, "SIGTHAW: special signal used by CPR"},
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/* 36 */ {0, "SIGCANCEL: reserved signal for thread cancellation"},
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/* 37 */ {_SigNotify, "SIGLOST: resource lost (eg, record-lock lost)"},
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/* 38 */ {_SigNotify, "SIGXRES: resource control exceeded"},
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/* 39 */ {_SigNotify, "SIGJVM1: reserved signal for Java Virtual Machine"},
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/* 40 */ {_SigNotify, "SIGJVM2: reserved signal for Java Virtual Machine"},
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/* TODO(aram): what should be do about these signals? _SigDefault or _SigNotify? is this set static? */
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/* 41 */ {_SigNotify, "real time signal"},
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/* 42 */ {_SigNotify, "real time signal"},
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/* 43 */ {_SigNotify, "real time signal"},
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/* 44 */ {_SigNotify, "real time signal"},
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/* 45 */ {_SigNotify, "real time signal"},
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/* 46 */ {_SigNotify, "real time signal"},
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/* 47 */ {_SigNotify, "real time signal"},
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/* 48 */ {_SigNotify, "real time signal"},
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/* 49 */ {_SigNotify, "real time signal"},
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/* 50 */ {_SigNotify, "real time signal"},
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/* 51 */ {_SigNotify, "real time signal"},
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/* 52 */ {_SigNotify, "real time signal"},
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/* 53 */ {_SigNotify, "real time signal"},
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/* 54 */ {_SigNotify, "real time signal"},
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/* 55 */ {_SigNotify, "real time signal"},
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/* 56 */ {_SigNotify, "real time signal"},
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/* 57 */ {_SigNotify, "real time signal"},
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/* 58 */ {_SigNotify, "real time signal"},
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/* 59 */ {_SigNotify, "real time signal"},
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/* 60 */ {_SigNotify, "real time signal"},
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/* 61 */ {_SigNotify, "real time signal"},
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/* 62 */ {_SigNotify, "real time signal"},
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/* 63 */ {_SigNotify, "real time signal"},
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/* 64 */ {_SigNotify, "real time signal"},
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/* 65 */ {_SigNotify, "real time signal"},
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/* 66 */ {_SigNotify, "real time signal"},
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/* 67 */ {_SigNotify, "real time signal"},
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/* 68 */ {_SigNotify, "real time signal"},
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/* 69 */ {_SigNotify, "real time signal"},
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/* 70 */ {_SigNotify, "real time signal"},
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/* 71 */ {_SigNotify, "real time signal"},
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/* 72 */ {_SigNotify, "real time signal"},
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}
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