Don't call sigtimedwait for scoped_ignore_sigttou
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