[RFC] 00/10 non-stop support (and linux native support)

[Pedro Alves <pedro at codesourcery dot com>]

Hi,

This series adds inferior control support for non-stop mode, and
then adds linux native support on top.

There are still ongoing discussions on how to activate and
expose to frontends the non-stop support.  MI seems to getting
stable enough now.

This series adds no docs yet, as they are yet to be writen, but
we'll get to it.

In the meantime, I'd like to get comments on the rest of the
code, and maybe even a couple of testers.

One patch I'm not adding in this series , is the support
for GDB to *not* switch threads automatically on events
(in non-stop mode), and what to do when the current thread exits.
I'll post those separatelly.

MI/non-stop is our main focus, but CLI works a bit too, although
there are a lot of rough edges:

Debugging a multi-threaded app has these looks:

(gdb) r&
Starting program: /home/pedro/gdb/tests/threads32
(gdb) [Thread debugging using libthread_db enabled]
[New LWP 23453]
[New LWP 23454]
info threads
  3 Thread 0xf7603b90 (LWP 23454)  (running)
  2 Thread 0xf7e04b90 (LWP 23453)  (running)
* 1 LWP 23450  (running)
(gdb) thread 2
[Switching to thread 2 (Thread 0xf7e04b90 (LWP 23453))] (running)
(gdb) interrupt
(gdb)
Program received signal SIGINT, Interrupt.
[Switching to Thread 0xf7e04b90 (LWP 23453)]
0xffffe410 in __kernel_vsyscall ()
b 63
Breakpoint 1 at 0x80485a6: file threads.c, line 63.
(gdb) info threads
During symbol reading, incomplete CFI data; unspecified registers (e.g., eax) 
at 0xffffe411.
  3 Thread 0xf7603b90 (LWP 23454)  (running)
* 2 Thread 0xf7e04b90 (LWP 23453)  0xffffe410 in __kernel_vsyscall ()
  1 Thread 0xf7e056b0 (LWP 23450)  (running)
(gdb) c&
Continuing.
(gdb)
Breakpoint 1, thread_function0 (arg=0x0) at threads.c:63
63              (*myp) ++;
info threads
  3 Thread 0xf7603b90 (LWP 23454)  (running)
* 2 Thread 0xf7e04b90 (LWP 23453)  thread_function0 (arg=0x0) at threads.c:63
  1 Thread 0xf7e056b0 (LWP 23450)  (running)

(gdb) b 80
Breakpoint 2 at 0x80485f0: file threads.c, line 80.
(gdb) [Switching to Thread 0xf7603b90 (LWP 23454)]

Breakpoint 2, thread_function1 (arg=0x1) at threads.c:80
80              (*myp) ++;
info threads
* 3 Thread 0xf7603b90 (LWP 23454)  thread_function1 (arg=0x1) at threads.c:80
  2 Thread 0xf7e04b90 (LWP 23453)  thread_function0 (arg=0x0) at threads.c:63
  1 Thread 0xf7e056b0 (LWP 23450)  (running)
(gdb)                                         


The series is layed out as:

001 Add "executing" property

 Adding an "executing" property to GDB's view of threads.

002 Don't trim ptids on fork/exec

 Don't trim ptids on follow fork/vfork/exec, so the previous
 patch works in those cases.

003 Add non-stop global

 Add a non_stop global, and associated "set/show non-stop"
 commands.  Split out or core non-stop, because the following
 patch uses it.

004 per-thread commands in non-stop mode

 In non-stop mode, we can have one exec command active per-thread,
 and they're independant, while in all-stop, there can only be one,
 and it's global.  This adds the necessary context-switching glue.

005 Expose context_switch

 In non-stop mode, whenever we switch threads, and because each
 is handled independently of the others, we need to
 context-switch outside of infrun.c (e.g., "thread n" command,
 thread apply all, "continue --all".)

006 Don't rely on ecs->wait_for_more before fetching the event

 ecs->wait_for_more is being checked before fetching the pending
 event from the target, and if not, then we're clearing some state.
 This patch avoids the need to context switching that variable, by
 moving that code in questiong to proceed. 

007 non-stop inferior control

 This adds the inferior control in non-stop mode.

008 Enable thread commands

 Now that "info threads" and "thread" are "running" thread aware,
 enable them.

009 Add "continue --all"

 This adds "continue --all" for non-stop mode.

010 non-stop for linux native

 Adds non-stop support for linux native.

-- 
Pedro Alves