[binutils-gdb] waiting_for_stop_reply around remote_fileio_request

[Yao Qi <qiyao at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e42e5352d1d1e8a262178f606a5df3d0d988f78a

commit e42e5352d1d1e8a262178f606a5df3d0d988f78a
Author: Yao Qi <yao.qi@linaro.org>
Date:   Thu Feb 4 15:09:09 2016 +0000

    waiting_for_stop_reply around remote_fileio_request
    
    Hi,
    I see this error when GDB connects with qemu,
    
    (gdb) n
    ....
    Sending packet: $vCont;c#a8...Ack
    Packet received: Ffstat,00000001,f6fff038
    Cannot execute this command while the target is running.
    Use the "interrupt" command to stop the target
    and then try again.
    
    looks we don't set rs->waiting_for_stop_reply to zero
    before handle fileio request,
    
     #10 0x00000000005edb64 in target_write (len=64, offset=4143968312, buf=0x7fffffffd570 "\375\377\377\377", annex=0x0, object=TARGET_OBJECT_MEMORY,
        ops=<optimised out>) at /home/yao/SourceCode/gnu/gdb/git/gdb/target.c:1922
     #11 target_write_memory (memaddr=memaddr@entry=4143968312, myaddr=myaddr@entry=0x7fffffffd6a0 "", len=len@entry=64)
        at /home/yao/SourceCode/gnu/gdb/git/gdb/target.c:1500
     #12 0x00000000004b2b41 in remote_fileio_func_fstat (buf=0x127b258 "") at /home/yao/SourceCode/gnu/gdb/git/gdb/remote-fileio.c:1037
     #13 0x00000000004b1878 in do_remote_fileio_request (uiout=<optimised out>, buf_arg=buf_arg@entry=0x127b240)
        at /home/yao/SourceCode/gnu/gdb/git/gdb/remote-fileio.c:1204
     #14 0x00000000005b8c7c in catch_exceptions_with_msg (func_uiout=<optimised out>, func=func@entry=0x4b1800 <do_remote_fileio_request>,
        func_args=func_args@entry=0x127b240, gdberrmsg=gdberrmsg@entry=0x0, mask=mask@entry=RETURN_MASK_ALL)
        at /home/yao/SourceCode/gnu/gdb/git/gdb/exceptions.c:187
     #15 0x00000000005b8dea in catch_exceptions (uiout=<optimised out>, func=func@entry=0x4b1800 <do_remote_fileio_request>, func_args=func_args@entry=0x127b240,
        mask=mask@entry=RETURN_MASK_ALL) at /home/yao/SourceCode/gnu/gdb/git/gdb/exceptions.c:167
     #16 0x00000000004b2fff in remote_fileio_request (buf=0x127b240 "Xf6fff038,0:", ctrlc_pending_p=0) at /home/yao/SourceCode/gnu/gdb/git/gdb/remote-fileio.c:1255
     #17 0x0000000000496f12 in remote_wait_as (ptid=..., status=0x7fffffffdb20, options=1) at /home/yao/SourceCode/gnu/gdb/git/gdb/remote.c:6997
    
    however, we did set rs->waiting_for_stop_reply to zero before Luis's
    patch https://sourceware.org/ml/gdb-patches/2015-10/msg00336.html
    
    In fact, Luis's patch v1
    https://sourceware.org/ml/gdb-patches/2015-08/msg00809.html is about
    setting rs->waiting_for_stop_reply back to one after
    remote_fileio_request, which is correct.  However during the review, the
    patch is changed and ends up with "not setting rs->waiting_for_stop_reply
    to zero".
    
    I manually test GDB, but I don't have a way to run regression tests.
    
    gdb:
    
    2016-02-04  Yao Qi  <yao.qi@linaro.org>
    
    	* remote.c (remote_wait_as): Set rs->waiting_for_stop_reply to
    	0 before handling 'F' and set it back afterwards.

Diff:
---
 gdb/ChangeLog | 5 +++++
 gdb/remote.c  | 8 ++++++++
 2 files changed, 13 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 829a48c..a2b0d39 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2016-02-04  Yao Qi  <yao.qi@linaro.org>
+
+	* remote.c (remote_wait_as): Set rs->waiting_for_stop_reply to
+	0 before handling 'F' and set it back afterwards.
+
 2016-02-02  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* ui-out.c (MAX_UI_OUT_LEVELS): Remove.
diff --git a/gdb/remote.c b/gdb/remote.c
index 8831b50..b1af8aa 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -6984,8 +6984,16 @@ remote_wait_as (ptid_t ptid, struct target_waitstatus *status, int options)
       status->value.sig = GDB_SIGNAL_0;
       break;
     case 'F':		/* File-I/O request.  */
+      /* GDB may access the inferior memory while handling the File-I/O
+	 request, but we don't want GDB accessing memory while waiting
+	 for a stop reply.  See the comments in putpkt_binary.  Set
+	 waiting_for_stop_reply to 0 temporarily.  */
+      rs->waiting_for_stop_reply = 0;
       remote_fileio_request (buf, rs->ctrlc_pending_p);
       rs->ctrlc_pending_p = 0;
+      /* GDB handled the File-I/O request, and the target is running
+	 again.  Keep waiting for events.  */
+      rs->waiting_for_stop_reply = 1;
       break;
     case 'N': case 'T': case 'S': case 'X': case 'W':
       {