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336b30e58a
Because SIGTTOU is sent to the whole process instead of to a specific thread, consuming a pending SIGTTOU in the destructor of scoped_ignore_sigttou could consume a SIGTTOU signal raised due to actions done by some other thread. Simply avoid sigtimedwait in scoped_ignore_sigttou, thus plugging the race. This works because we know that when the thread writes to the terminal and the signal is blocked, the kernel does not raise the signal at all. Tested on GNU/Linux, Solaris 11 and FreeBSD. gdb/ChangeLog: yyyy-mm-dd Pedro Alves <pedro@palves.net> * scoped_ignore_signal.h (scoped_ignore_signal): Add ConsumePending template parameter. (scoped_ignore_signal::~scoped_ignore_signal): Skip calling sigtimedwait if ConsumePending is false. (scoped_ignore_sigpipe): Initialize with ConsumePending=true. * scoped_ignore_sigttou.h (scoped_ignore_sigttou) <m_ignore_signal>: Initialize with ConsumePending=false. Change-Id: I92f754dbc45c45819dce2ce68b8c067d8d5c61b1
88 lines
2.0 KiB
C++
88 lines
2.0 KiB
C++
/* Support for signoring SIGTTOU.
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Copyright (C) 2003-2021 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef SCOPED_IGNORE_SIGTTOU_H
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#define SCOPED_IGNORE_SIGTTOU_H
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#include "gdbsupport/scoped_ignore_signal.h"
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#include "gdbsupport/job-control.h"
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#ifdef SIGTTOU
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/* Simple wrapper that allows lazy initialization / destruction of T.
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Slightly more efficient than gdb::optional, because it doesn't
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carry storage to track whether the object has been initialized. */
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template<typename T>
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class lazy_init
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{
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public:
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void emplace ()
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{
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new (&m_u.obj) T ();
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}
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void reset ()
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{
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m_u.obj.~T ();
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}
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private:
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union u
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{
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/* Must define ctor/dtor if T has non-trivial ctor/dtor. */
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u () {}
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~u () {}
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T obj;
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} m_u;
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};
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/* RAII class used to ignore SIGTTOU in a scope. This isn't simply
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scoped_ignore_signal<SIGTTOU> because we want to check the
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`job_control' global. */
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class scoped_ignore_sigttou
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{
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public:
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scoped_ignore_sigttou ()
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{
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if (job_control)
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m_ignore_signal.emplace ();
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}
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~scoped_ignore_sigttou ()
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{
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if (job_control)
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m_ignore_signal.reset ();
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}
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DISABLE_COPY_AND_ASSIGN (scoped_ignore_sigttou);
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private:
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lazy_init<scoped_ignore_signal<SIGTTOU, false>> m_ignore_signal;
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};
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#else
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using scoped_ignore_sigttou = scoped_ignore_signal_nop;
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#endif
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#endif /* SCOPED_IGNORE_SIGTTOU_H */
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