* [PATCH][PR symtab/17855] Fix.
@ 2015-01-20 6:27 Doug Evans
2015-01-22 11:42 ` Pedro Alves
0 siblings, 1 reply; 7+ messages in thread
From: Doug Evans @ 2015-01-20 6:27 UTC (permalink / raw)
To: gdb-patches, brobecker
Hi.
This patch fixes symtab/17855.
Basically the issue is that breakpoint_re_set is currently being called
before observer_notify_new_objfile (NULL), and thus the ada symbol
cache (and the general symbol cache of a separate patch) aren't being
flushed first, so that when breakpoints are reset symbol lookup is being
done on a stale cache.
Regression tested on amd64-linux.
2015-01-19 Doug Evans <xdje42@gmail.com>
PR symtab/17855
* symfile.c (clear_symtab_users): Notify observers of change before
calling breakpoint_re_set.
diff --git a/gdb/symfile.c b/gdb/symfile.c
index d55e361..ad481de 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -3023,6 +3023,12 @@ clear_symtab_users (int add_flags)
/* Someday, we should do better than this, by only blowing away
the things that really need to be blown. */
+ /* Notify anyone listening that the previous loaded symtab(s) are invalid.
+ It is important to do this before calling breakpoint_re_set as the latter
+ will try to look up symbols, and for example the symbol cache needs to
+ be flushed first. */
+ observer_notify_new_objfile (NULL);
+
/* Clear the "current" symtab first, because it is no longer valid.
breakpoint_re_set may try to access the current symtab. */
clear_current_source_symtab_and_line ();
@@ -3032,7 +3038,6 @@ clear_symtab_users (int add_flags)
breakpoint_re_set ();
clear_last_displayed_sal ();
clear_pc_function_cache ();
- observer_notify_new_objfile (NULL);
/* Clear globals which might have pointed into a removed objfile.
FIXME: It's not clear which of these are supposed to persist
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
2015-01-20 6:27 [PATCH][PR symtab/17855] Fix Doug Evans
@ 2015-01-22 11:42 ` Pedro Alves
2015-01-22 15:37 ` Doug Evans
2015-01-29 8:00 ` Doug Evans
0 siblings, 2 replies; 7+ messages in thread
From: Pedro Alves @ 2015-01-22 11:42 UTC (permalink / raw)
To: Doug Evans, gdb-patches, brobecker
On 01/20/2015 06:26 AM, Doug Evans wrote:
> Hi.
>
> This patch fixes symtab/17855.
> Basically the issue is that breakpoint_re_set is currently being called
> before observer_notify_new_objfile (NULL), and thus the ada symbol
> cache (and the general symbol cache of a separate patch) aren't being
> flushed first, so that when breakpoints are reset symbol lookup is being
> done on a stale cache.
>
> Regression tested on amd64-linux.
>
> 2015-01-19 Doug Evans <xdje42@gmail.com>
>
> PR symtab/17855
> * symfile.c (clear_symtab_users): Notify observers of change before
> calling breakpoint_re_set.
>
> diff --git a/gdb/symfile.c b/gdb/symfile.c
> index d55e361..ad481de 100644
> --- a/gdb/symfile.c
> +++ b/gdb/symfile.c
> @@ -3023,6 +3023,12 @@ clear_symtab_users (int add_flags)
> /* Someday, we should do better than this, by only blowing away
> the things that really need to be blown. */
>
> + /* Notify anyone listening that the previous loaded symtab(s) are invalid.
> + It is important to do this before calling breakpoint_re_set as the latter
> + will try to look up symbols, and for example the symbol cache needs to
> + be flushed first. */
> + observer_notify_new_objfile (NULL);
> +
> /* Clear the "current" symtab first, because it is no longer valid.
> breakpoint_re_set may try to access the current symtab. */
> clear_current_source_symtab_and_line ();
> @@ -3032,7 +3038,6 @@ clear_symtab_users (int add_flags)
> breakpoint_re_set ();
> clear_last_displayed_sal ();
> clear_pc_function_cache ();
> - observer_notify_new_objfile (NULL);
Looking at the whole function, ISTM that the breakpoint_re_set
call should move further down. I can imagine that breakpoint_re_set
could well hit a stale pc function cache, cleared only after by
clear_pc_function_cache. breakpoint.c:parse_breakpoint_sals also
references the last displayed sal. One would hope that breakpoint
re-set is independent of that, though the existing comment about
breakpoint_re_set accessing the current symtab leaves me
wondering. WDYT?
Thanks,
Pedro Alves
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
2015-01-22 11:42 ` Pedro Alves
@ 2015-01-22 15:37 ` Doug Evans
2015-01-29 8:00 ` Doug Evans
1 sibling, 0 replies; 7+ messages in thread
From: Doug Evans @ 2015-01-22 15:37 UTC (permalink / raw)
To: Pedro Alves; +Cc: gdb-patches, Joel Brobecker
On Thu, Jan 22, 2015 at 3:41 AM, Pedro Alves <palves@redhat.com> wrote:
> Looking at the whole function, ISTM that the breakpoint_re_set
> call should move further down. I can imagine that breakpoint_re_set
> could well hit a stale pc function cache, cleared only after by
> clear_pc_function_cache. breakpoint.c:parse_breakpoint_sals also
> references the last displayed sal. One would hope that breakpoint
> re-set is independent of that, though the existing comment about
> breakpoint_re_set accessing the current symtab leaves me
> wondering. WDYT?
Fine by me.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
2015-01-22 11:42 ` Pedro Alves
2015-01-22 15:37 ` Doug Evans
@ 2015-01-29 8:00 ` Doug Evans
2015-01-29 8:12 ` Joel Brobecker
1 sibling, 1 reply; 7+ messages in thread
From: Doug Evans @ 2015-01-29 8:00 UTC (permalink / raw)
To: Pedro Alves; +Cc: gdb-patches, brobecker
Pedro Alves <palves@redhat.com> writes:
> On 01/20/2015 06:26 AM, Doug Evans wrote:
>> Hi.
>>
>> This patch fixes symtab/17855.
>> Basically the issue is that breakpoint_re_set is currently being called
>> before observer_notify_new_objfile (NULL), and thus the ada symbol
>> cache (and the general symbol cache of a separate patch) aren't being
>> flushed first, so that when breakpoints are reset symbol lookup is being
>> done on a stale cache.
>>
>> Regression tested on amd64-linux.
>>
>> 2015-01-19 Doug Evans <xdje42@gmail.com>
>>
>> PR symtab/17855
>> * symfile.c (clear_symtab_users): Notify observers of change before
>> calling breakpoint_re_set.
>>
>> diff --git a/gdb/symfile.c b/gdb/symfile.c
>> index d55e361..ad481de 100644
>> --- a/gdb/symfile.c
>> +++ b/gdb/symfile.c
>> @@ -3023,6 +3023,12 @@ clear_symtab_users (int add_flags)
>> /* Someday, we should do better than this, by only blowing away
>> the things that really need to be blown. */
>>
>> + /* Notify anyone listening that the previous loaded symtab(s) are invalid.
>> + It is important to do this before calling breakpoint_re_set as the latter
>> + will try to look up symbols, and for example the symbol cache needs to
>> + be flushed first. */
>> + observer_notify_new_objfile (NULL);
>> +
>> /* Clear the "current" symtab first, because it is no longer valid.
>> breakpoint_re_set may try to access the current symtab. */
>> clear_current_source_symtab_and_line ();
>> @@ -3032,7 +3038,6 @@ clear_symtab_users (int add_flags)
>> breakpoint_re_set ();
>> clear_last_displayed_sal ();
>> clear_pc_function_cache ();
>> - observer_notify_new_objfile (NULL);
>
> Looking at the whole function, ISTM that the breakpoint_re_set
> call should move further down. I can imagine that breakpoint_re_set
> could well hit a stale pc function cache, cleared only after by
> clear_pc_function_cache. breakpoint.c:parse_breakpoint_sals also
> references the last displayed sal. One would hope that breakpoint
> re-set is independent of that, though the existing comment about
> breakpoint_re_set accessing the current symtab leaves me
> wondering. WDYT?
>
> Thanks,
> Pedro Alves
Like so?
2015-01-28 Doug Evans <xdje42@gmail.com>
PR symtab/17855
* symfile.c (clear_symtab_users): Move call to breakpoint_re_set
closer to end.
diff --git a/gdb/symfile.c b/gdb/symfile.c
index d55e361..bad244c 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -3023,13 +3023,8 @@ clear_symtab_users (int add_flags)
/* Someday, we should do better than this, by only blowing away
the things that really need to be blown. */
- /* Clear the "current" symtab first, because it is no longer valid.
- breakpoint_re_set may try to access the current symtab. */
clear_current_source_symtab_and_line ();
-
clear_displays ();
- if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
- breakpoint_re_set ();
clear_last_displayed_sal ();
clear_pc_function_cache ();
observer_notify_new_objfile (NULL);
@@ -3040,9 +3035,19 @@ clear_symtab_users (int add_flags)
expression_context_block = NULL;
innermost_block = NULL;
+ /* Now that most everything has been reset, reset any existing breakpoints.
+ Reasons for doing this after the above are that breakpoint resetting may
+ involve:
+ - reading the current source symtab and line,
+ - reading the last displayed sal,
+ - reading the pc function cache,
+ - symbol lookup which requires, for example, invalidating any caches
+ first. */
+ if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
+ breakpoint_re_set ();
+
/* Varobj may refer to old symbols, perform a cleanup. */
varobj_invalidate ();
-
}
static void
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
2015-01-29 8:00 ` Doug Evans
@ 2015-01-29 8:12 ` Joel Brobecker
2015-01-29 10:01 ` Doug Evans
0 siblings, 1 reply; 7+ messages in thread
From: Joel Brobecker @ 2015-01-29 8:12 UTC (permalink / raw)
To: Doug Evans; +Cc: Pedro Alves, gdb-patches
[-- Attachment #1: Type: text/plain, Size: 2115 bytes --]
Aargh - I was working on it just now because I wasn't sure if anyone
felt they "had the ball on their court".
> Like so?
>
> 2015-01-28 Doug Evans <xdje42@gmail.com>
>
> PR symtab/17855
> * symfile.c (clear_symtab_users): Move call to breakpoint_re_set
> closer to end.
What I've tested is moving the call last, as shown in the attached
diff. Not technically necessarily better, but as the comment explains,
I move it last so that it's after we've purged all relevant caches.
That way, the function is organized in two rough sections:
- do purges first;
- do updates next.
Your comment is a lot more detailed, I like it.
> diff --git a/gdb/symfile.c b/gdb/symfile.c
> index d55e361..bad244c 100644
> --- a/gdb/symfile.c
> +++ b/gdb/symfile.c
> @@ -3023,13 +3023,8 @@ clear_symtab_users (int add_flags)
> /* Someday, we should do better than this, by only blowing away
> the things that really need to be blown. */
>
> - /* Clear the "current" symtab first, because it is no longer valid.
> - breakpoint_re_set may try to access the current symtab. */
> clear_current_source_symtab_and_line ();
> -
> clear_displays ();
> - if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
> - breakpoint_re_set ();
> clear_last_displayed_sal ();
> clear_pc_function_cache ();
> observer_notify_new_objfile (NULL);
> @@ -3040,9 +3035,19 @@ clear_symtab_users (int add_flags)
> expression_context_block = NULL;
> innermost_block = NULL;
>
> + /* Now that most everything has been reset, reset any existing breakpoints.
> + Reasons for doing this after the above are that breakpoint resetting may
> + involve:
> + - reading the current source symtab and line,
> + - reading the last displayed sal,
> + - reading the pc function cache,
> + - symbol lookup which requires, for example, invalidating any caches
> + first. */
> + if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
> + breakpoint_re_set ();
> +
> /* Varobj may refer to old symbols, perform a cleanup. */
> varobj_invalidate ();
> -
> }
>
> static void
>
>
>
--
Joel
[-- Attachment #2: bp-re-set.diff --]
[-- Type: text/x-diff, Size: 789 bytes --]
diff --git a/gdb/symfile.c b/gdb/symfile.c
index d55e361..04a5c58 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -3028,8 +3028,6 @@ clear_symtab_users (int add_flags)
clear_current_source_symtab_and_line ();
clear_displays ();
- if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
- breakpoint_re_set ();
clear_last_displayed_sal ();
clear_pc_function_cache ();
observer_notify_new_objfile (NULL);
@@ -3043,6 +3041,10 @@ clear_symtab_users (int add_flags)
/* Varobj may refer to old symbols, perform a cleanup. */
varobj_invalidate ();
+ /* Now that the various caches have been cleared, we can re_set
+ our breakpoints without risking it using stale data. */
+ if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
+ breakpoint_re_set ();
}
static void
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
2015-01-29 8:12 ` Joel Brobecker
@ 2015-01-29 10:01 ` Doug Evans
[not found] ` <m3r3ualkvb.fsf@sspiff.org>
0 siblings, 1 reply; 7+ messages in thread
From: Doug Evans @ 2015-01-29 10:01 UTC (permalink / raw)
To: Joel Brobecker; +Cc: Pedro Alves, gdb-patches
On Wed, Jan 28, 2015 at 11:19 PM, Joel Brobecker <brobecker@adacore.com> wrote:
> Aargh - I was working on it just now because I wasn't sure if anyone
> felt they "had the ball on their court".
>
>> Like so?
>>
>> 2015-01-28 Doug Evans <xdje42@gmail.com>
>>
>> PR symtab/17855
>> * symfile.c (clear_symtab_users): Move call to breakpoint_re_set
>> closer to end.
>
> What I've tested is moving the call last, as shown in the attached
> diff. Not technically necessarily better, but as the comment explains,
> I move it last so that it's after we've purged all relevant caches.
> That way, the function is organized in two rough sections:
> - do purges first;
> - do updates next.
> Your comment is a lot more detailed, I like it.
I think yours is fine too.
I'm ok with using it.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH][PR symtab/17855] Fix.
[not found] ` <m3r3ualkvb.fsf@sspiff.org>
@ 2015-02-03 17:02 ` Pedro Alves
0 siblings, 0 replies; 7+ messages in thread
From: Pedro Alves @ 2015-02-03 17:02 UTC (permalink / raw)
To: Doug Evans, Joel Brobecker; +Cc: gdb-patches
On 01/31/2015 10:07 PM, Doug Evans wrote:
> Doug Evans <xdje42@gmail.com> writes:
>> On Wed, Jan 28, 2015 at 11:19 PM, Joel Brobecker <brobecker@adacore.com> wrote:
>>> Your comment is a lot more detailed, I like it.
>>
>> I think yours is fine too.
>> I'm ok with using it.
>
> Hi.
> There's value in the simplicity of your approach so I
> committed it to trunk and the branch.
>
Thanks guys.
Pedro Alves
^ permalink raw reply [flat|nested] 7+ messages in thread
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2015-01-20 6:27 [PATCH][PR symtab/17855] Fix Doug Evans
2015-01-22 11:42 ` Pedro Alves
2015-01-22 15:37 ` Doug Evans
2015-01-29 8:00 ` Doug Evans
2015-01-29 8:12 ` Joel Brobecker
2015-01-29 10:01 ` Doug Evans
[not found] ` <m3r3ualkvb.fsf@sspiff.org>
2015-02-03 17:02 ` Pedro Alves
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