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[patch] Multi-architecture debugging regression (Re: performance of multithreading gets gradually worse under gdb)
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: pedro at codesourcery dot com (Pedro Alves)
- Cc: gdb-patches at sourceware dot org
- Date: Wed, 26 Oct 2011 19:14:11 +0200 (CEST)
- Subject: [patch] Multi-architecture debugging regression (Re: performance of multithreading gets gradually worse under gdb)
Pedro Alves wrote:
> 2011-02-04 Pedro Alves <firstname.lastname@example.org>
> * regcache.c (registers_changed_ptid): Don't explictly always
> clear `current_regcache'. Only clear current_thread_ptid and
> current_thread_arch when PTID matches. Only reinit the frame
> cache if PTID matches the current inferior_ptid. Move alloca(0)
> call to ...
> (registers_changed): ... here.
It seems this patch broke multi-architecture debugging on Cell/B.E. since
the cached thread architecture is sometimes not invalidated when it should
be. This happens when resume is called with a PTID that refers to all
threads of a process.
The problem is that your patch specifically handles PTIDs that refer to
one particular thread, and also handles a wildcard PTID that refers to
all threads of all processes. But it does not handle PTIDs that refer
to all threads of one single process.
I think the code should simply use ptid_match here (as is already done
elsewhere, even in this same function). This fixes the problem on
Cell/B.E. for me ...
Tested on powerpc-linux (Cell/B.E.).
Does this look OK to you?
* regcache.c (registers_changed_ptid): Invalidate thread architecture
and frame caches if PTID refers to all threads of a process.
RCS file: /cvs/src/src/gdb/regcache.c,v
retrieving revision 1.194
diff -u -p -r1.194 regcache.c
--- gdb/regcache.c 11 Oct 2011 18:35:25 -0000 1.194
+++ gdb/regcache.c 24 Oct 2011 11:02:46 -0000
@@ -548,7 +548,6 @@ void
registers_changed_ptid (ptid_t ptid)
struct regcache_list *list, **list_link;
- int wildcard = ptid_equal (ptid, minus_one_ptid);
list = current_regcache;
list_link = ¤t_regcache;
@@ -569,13 +568,13 @@ registers_changed_ptid (ptid_t ptid)
list = *list_link;
- if (wildcard || ptid_equal (ptid, current_thread_ptid))
+ if (ptid_match (current_thread_ptid, ptid))
current_thread_ptid = null_ptid;
current_thread_arch = NULL;
- if (wildcard || ptid_equal (ptid, inferior_ptid))
+ if (ptid_match (inferior_ptid, ptid))
/* We just deleted the regcache of the current thread. Need to
forget about any frames we have cached, too. */
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE