[patch/gdbserver] Handle early interrupts

[patch/gdbserver] Handle early interrupts

[Daniel Jacobowitz]

This patch lets gdbserver start expecting control-C as soon as we begin
resuming threads, instead of as soon as we begin waiting.  On slow targets,
especially if one of the threads is scheduled right after the PTRACE_CONT
and before gdbserver has finished waking its siblings, there can be a long
delay.  Until this arbitrary, sometimes very long, delay has passed, any
control-C sent by the client will be ignored.  The easy solution is to
enable, but block, SIGIO; then unblock it when we're ready and the OS
will automatically deliver it then.

Will commit in a little while.  Tested on arm-linux using gdbserver
(I've forgotten to mention that for the last few patches, but it's true of
all of them).

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

2004-02-28  Daniel Jacobowitz  <drow@mvista.com>

	* linux-low.c (linux_wait): Unblock async I/O.
	(linux_resume): Block and enable async I/O.
	* remote-utils.c (block_async_io, unblock_async_io): New functions.
	* server.h (block_async_io, unblock_async_io): Add prototypes.

Index: gdb/gdbserver/linux-low.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/gdbserver/linux-low.c,v
retrieving revision 1.27
diff -u -p -r1.27 linux-low.c
--- gdb/gdbserver/linux-low.c	31 Jan 2004 22:19:31 -0000	1.27
+++ gdb/gdbserver/linux-low.c	27 Feb 2004 21:34:28 -0000
@@ -662,6 +662,7 @@ retry:
     }
 
   enable_async_io ();
+  unblock_async_io ();
   w = linux_wait_for_event (child);
   stop_all_processes ();
   disable_async_io ();
@@ -1017,7 +1018,11 @@ linux_resume (struct thread_resume *resu
   if (pending_flag)
     for_each_inferior (&all_threads, linux_queue_one_thread);
   else
-    for_each_inferior (&all_threads, linux_continue_one_thread);
+    {
+      block_async_io ();
+      enable_async_io ();
+      for_each_inferior (&all_threads, linux_continue_one_thread);
+    }
 }
 
 #ifdef HAVE_LINUX_USRREGS
Index: gdb/gdbserver/remote-utils.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/gdbserver/remote-utils.c,v
retrieving revision 1.17
diff -u -p -r1.17 remote-utils.c
--- gdb/gdbserver/remote-utils.c	5 Jun 2003 14:26:58 -0000	1.17
+++ gdb/gdbserver/remote-utils.c	27 Feb 2004 20:54:11 -0000
@@ -366,6 +368,24 @@ input_interrupt (int unused)
 }
 
 void
+block_async_io (void)
+{
+  sigset_t sigio_set;
+  sigemptyset (&sigio_set);
+  sigaddset (&sigio_set, SIGIO);
+  sigprocmask (SIG_BLOCK, &sigio_set, NULL);
+}
+
+void
+unblock_async_io (void)
+{
+  sigset_t sigio_set;
+  sigemptyset (&sigio_set);
+  sigaddset (&sigio_set, SIGIO);
+  sigprocmask (SIG_UNBLOCK, &sigio_set, NULL);
+}
+
+void
 enable_async_io (void)
 {
   signal (SIGIO, input_interrupt);
Index: gdb/gdbserver/server.h
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/gdbserver/server.h,v
retrieving revision 1.13
diff -u -p -r1.13 server.h
--- gdb/gdbserver/server.h	29 Jun 2003 04:01:39 -0000	1.13
+++ gdb/gdbserver/server.h	27 Feb 2004 16:15:53 -0000
@@ -134,6 +134,8 @@ void write_ok (char *buf);
 void write_enn (char *buf);
 void enable_async_io (void);
 void disable_async_io (void);
+void unblock_async_io (void);
+void block_async_io (void);
 void convert_ascii_to_int (char *from, char *to, int n);
 void convert_int_to_ascii (char *from, char *to, int n);
 void new_thread_notify (int id);

Re: [patch/gdbserver] Handle early interrupts

[Daniel Jacobowitz]

On Sat, Feb 28, 2004 at 01:13:59PM -0500, Daniel Jacobowitz wrote:
> This patch lets gdbserver start expecting control-C as soon as we begin
> resuming threads, instead of as soon as we begin waiting.  On slow targets,
> especially if one of the threads is scheduled right after the PTRACE_CONT
> and before gdbserver has finished waking its siblings, there can be a long
> delay.  Until this arbitrary, sometimes very long, delay has passed, any
> control-C sent by the client will be ignored.  The easy solution is to
> enable, but block, SIGIO; then unblock it when we're ready and the OS
> will automatically deliver it then.
> 
> Will commit in a little while.  Tested on arm-linux using gdbserver
> (I've forgotten to mention that for the last few patches, but it's true of
> all of them).

> 2004-02-28  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* linux-low.c (linux_wait): Unblock async I/O.
> 	(linux_resume): Block and enable async I/O.
> 	* remote-utils.c (block_async_io, unblock_async_io): New functions.
> 	* server.h (block_async_io, unblock_async_io): Add prototypes.

Committed to HEAD.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer