FreeChainXenon/binutils-gdb
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[GDBserver] Block and unblock SIGIO

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Nowadays, GDBserver disables async io (by ignoring SIGIO) when process
a serial event, and enables async io (by installing signal handler) when
resume the inferior and wait.  GDBserver may miss SIGIO (by interrupt)
and doesn't process SIGIO in time, which is shown by
gdb.base/interrupt-noterm.exp.  In the test, GDB sends "continue &" and
then "interrupt".  if '\003' arrives at a period between GDBserver
receives vCont;c and enables async io, SIGIO is ignored because signal
handler isn't installed.  GDBserver waits for the inferior and can not
notice '\003' until it returns from wait.

This patch changes the code to install SIGIO handler early, but block
and unblock SIGIO as needed.  In this way, we don't remove SIGIO
handler, so SIGIO can't be ignored.  However, GDBserver needs to
remove the signal handler when connection is closed.

gdb/gdbserver:

2016-01-26  Yao Qi  <yao.qi@linaro.org>

	* remote-utils.c (remote_close) [!USE_WIN32API]: Ignore SIGIO.
	(unblock_async_io): Rename to ...
	(block_unblock_async_io): ... it.  New function.
	(enable_async_io): Don't install SIGIO handler.  Unblock it
	instead.
	(disable_async_io): Don't ignore SIGIO.  Block it instead.
	(initialize_async_io): Install SIGIO handler.  Don't call
	unblock_async_io.
This commit is contained in:
Yao Qi 2016-01-26 13:50:22 +00:00
parent 18879fef17
commit 8b20733984
2 changed files with 30 additions and 14 deletions
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11
gdb/gdbserver/ChangeLog
View file

@ -1,3 +1,14 @@
2016-01-26 Yao Qi <yao.qi@linaro.org>
* remote-utils.c (remote_close) [!USE_WIN32API]: Ignore SIGIO.
(unblock_async_io): Rename to ...
(block_unblock_async_io): ... it. New function.
(enable_async_io): Don't install SIGIO handler. Unblock it
instead.
(disable_async_io): Don't ignore SIGIO. Block it instead.
(initialize_async_io): Install SIGIO handler. Don't call
unblock_async_io.
2016-01-26 Yao Qi <yao.qi@linaro.org>
* remote-utils.c (getpkt): If the buffer isn't empty, and the

33
gdb/gdbserver/remote-utils.c
View file

@ -402,6 +402,11 @@ remote_close (void)
{
delete_file_handler (remote_desc);
#ifndef USE_WIN32API
/* Remove SIGIO handler. */
signal (SIGIO, SIG_IGN);
#endif
#ifdef USE_WIN32API
closesocket (remote_desc);
#else
@ -775,19 +780,19 @@ check_remote_input_interrupt_request (void)
input_interrupt (0);
}
/* Asynchronous I/O support. SIGIO must be enabled when waiting, in order to
accept Control-C from the client, and must be disabled when talking to
the client. */
/* Asynchronous I/O support. SIGIO must be unblocked when waiting,
in order to accept Control-C from the client, and must be blocked
when talking to the client. */
static void
unblock_async_io (void)
block_unblock_async_io (int block)
{
#ifndef USE_WIN32API
sigset_t sigio_set;
sigemptyset (&sigio_set);
sigaddset (&sigio_set, SIGIO);
sigprocmask (SIG_UNBLOCK, &sigio_set, NULL);
sigprocmask (block ? SIG_BLOCK : SIG_UNBLOCK, &sigio_set, NULL);
#endif
}
@ -823,9 +828,8 @@ enable_async_io (void)
if (async_io_enabled)
return;
#ifndef USE_WIN32API
signal (SIGIO, input_interrupt);
#endif
block_unblock_async_io (0);
async_io_enabled = 1;
#ifdef __QNX__
nto_comctrl (1);
@ -839,9 +843,8 @@ disable_async_io (void)
if (!async_io_enabled)
return;
#ifndef USE_WIN32API
signal (SIGIO, SIG_IGN);
#endif
block_unblock_async_io (1);
async_io_enabled = 0;
#ifdef __QNX__
nto_comctrl (0);
@ -852,12 +855,14 @@ disable_async_io (void)
void
initialize_async_io (void)
{
/* Make sure that async I/O starts disabled. */
/* Make sure that async I/O starts blocked. */
async_io_enabled = 1;
disable_async_io ();
/* Make sure the signal is unblocked. */
unblock_async_io ();
/* Install the signal handler. */
#ifndef USE_WIN32API
signal (SIGIO, input_interrupt);
#endif
}
/* Internal buffer used by readchar.