gdb:

	* target.h (struct target_ops) <to_use_agent>: New field.
	(struct target_ops) <to_can_use_agent>: New field.
	(target_use_agent, target_can_use_agent): New macro.
	* target.c (update_current_target): Update.
	* remote.c: New enum `PACKET_QAgent'.
	(remote_protocol_features): Add a new element.
	(remote_use_agent, remote_can_use_agent): New.
	(init_remote_ops): Initialize field `can_use_agent' with
	remote_can_use_agent.  Intiailize field `use_agent' with
	remote_use_agent.
	* common/agent.c (use_agent): New global.
	* common/agent.h: Declare it.
	* tracepoint.c (info_static_tracepoint_markers_command): Add
	comment.
	* Makefile.in (SFILES): Add common/agent.c and agent.c.
	(COMMON_OBS): Add common/agent.o and agent.o
	(common-agent.o): New rule.
	* agent.c: New.

gdb/doc:
	* gdb.texinfo (In-Process Agent): New node.
	Document new commands.
	(General Query Packets): Add packet `QAgent'.

gdb/gdbserver:
	* linux-low.c (linux_supports_agent): New.
	(linux_target_ops): Initialize field `supports_agent' with
	linux_supports_agent.
	* target.h (struct target_ops) <supports_agent>: New.
	(target_supports_agent): New macro.
	* server.c (handle_general_set): Handle packet 'QAgent'.
	(handle_query): Send `QAgent+'.
	* Makefile.in (server.o): Depends on agent.h.

2 files changed, 77 insertions, 0 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 89ded13..f3e483f 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2012-03-03  Yao Qi  <yao@codesourcery.com>
+
+	* gdb.texinfo (In-Process Agent): New node.
+	Document new commands.
+	(General Query Packets): Add packet `QAgent'.
+
 2012-03-01  Maciej W. Rozycki  <macro@codesourcery.com>
 
 	* gdb.texinfo (MIPS Features): Add org.gnu.gdb.mips.dsp.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index e187b03..62c92e9 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -154,6 +154,7 @@ software in general.  We will miss him.
 * GDB/MI::                      @value{GDBN}'s Machine Interface.
 * Annotations::                 @value{GDBN}'s annotation interface.
 * JIT Interface::               Using the JIT debugging interface.
+* In-Process Agent::            In-Process Agent
 
 * GDB Bugs::                    Reporting bugs in @value{GDBN}
 
@@ -32286,6 +32287,63 @@ frame and to write out the values of the registers in the previous
 frame.  Both have a callback (@code{target_read}) to read bytes off the
 target's address space.
 
+@node In-Process Agent
+@chapter In-Process Agent
+@cindex debugging agent
+The traditional debugging model is conceptually low-speed, but works fine,
+because most bugs can be reproduced in debugging-mode execution.  However,
+as multi-core or many-core processors are becoming mainstream, and
+multi-threaded programs become more and more popular, there should be more
+and more bugs that only manifest themselves at normal-mode execution, for
+example, thread races, because debugger's interference with the program's
+timing may conceal the bugs.  On the other hand, in some applications,
+it is not feasible for the debugger to interrupt the program's execution
+long enough for the developer to learn anything helpful about its behavior.
+If the program's correctness depends on its real-time behavior, delays
+introduced by a debugger might cause the program to fail, even when the
+code itself is correct.  It is useful to be able to observe the program's
+behavior without interrupting it.
+
+Therefore, traditional debugging model is too intrusive to reproduce
+some bugs.  In order to reduce the interference with the program, we can
+reduce the number of operations performed by debugger.  The
+@dfn{In-Process Agent}, a shared library, is running within the same
+process with inferior, and is able to perform some debugging operations
+itself.  As a result, debugger is only involved when necessary, and
+performance of debugging can be improved accordingly.  Note that
+interference with program can be reduced but can't be removed completely,
+because the in-process agent will still stop or slow down the program.
+
+The in-process agent can interpret and execute Agent Expressions
+(@pxref{Agent Expressions}) during performing debugging operations.  The
+agent expressions can be used for different purposes, such as collecting
+data in tracepoints, and condition evaluation in breakpoints.
+
+@anchor{Control Agent}
+You can control whether the in-process agent is used as an aid for
+debugging with the following commands:
+
+@table @code
+@kindex set agent on
+@item set agent on
+Causes the in-process agent to perform some operations on behalf of the
+debugger.  Just which operations requested by the user will be done
+by the in-process agent depends on the its capabilities.  For example,
+if you request to evaluate breakpoint conditions in the in-process agent,
+and the in-process agent has such capability as well, then breakpoint
+conditions will be evaluated in the in-process agent.
+
+@kindex set agent off
+@item set agent off
+Disables execution of debugging operations by the in-process agent.  All
+of the operations will be performed by @value{GDBN}.
+
+@kindex show agent
+@item show agent
+Display the current setting of execution of debugging operations by
+the in-process agent.
+@end table
+
 @node GDB Bugs
 @chapter Reporting Bugs in @value{GDBN}
 @cindex bugs in @value{GDBN}
@@ -34623,6 +34681,11 @@ Here are the currently defined query and set packets:
 
 @table @samp
 
+@item QAgent:1
+@item QAgent:0
+Turn on or off the agent as a helper to perform some debugging operations
+delegated from @value{GDBN} (@pxref{Control Agent}).
+
 @item QAllow:@var{op}:@var{val}@dots{}
 @cindex @samp{QAllow} packet
 Specify which operations @value{GDBN} expects to request of the
@@ -35207,6 +35270,11 @@ These are the currently defined stub features and their properties:
 @tab @samp{-}
 @tab No
 
+@item @samp{QAgent}
+@tab No
+@tab @samp{-}
+@tab No
+
 @item @samp{QAllow}
 @tab No
 @tab @samp{-}
@@ -35345,6 +35413,9 @@ The remote stub accepts and implements the reverse step packet
 The remote stub understands the @samp{QTDPsrc} packet that supplies
 the source form of tracepoint definitions.
 
+@item QAgent
+The remote stub understands the @samp{QAgent} packet.
+
 @item QAllow
 The remote stub understands the @samp{QAllow} packet.