[Bug record/30073] New: [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[Bug record/30073] New: [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

            Bug ID: 30073
           Summary: [intel Efficient-core] FAIL: gdb.btrace/exception.exp:
                    flat (pattern 1)
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: record
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

I got a new laptop, build gdb and ran the gdb testsuite, and ran into:
...
(gdb) PASS: gdb.btrace/exception.exp: continue to breakpoint: cont to bp.2
gdb_expect_list pattern: /1     main\(\)^M
2       test\(\)^M
3       foo\(\)^M
4       bar\(\)^M
5       bad\(\)^M/
record function-call-history 1^M
1       main()^M
(gdb) FAIL: gdb.btrace/exception.exp: flat (pattern 1)
...

I could reproduce it sometimes, but not all the time, till I tried out using
taskset.

When using:
- taskset -c 0-3, the test-case passes.  
- taskset -c 4-11, the test-case fails.

The processor is a i7-1250U with 12 threads:
- 2 performance cores (I guess providing 2 threads per core), and
- 8 efficient cores.

So, I guess somehow it doesn't run properly on efficient cores.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |markus.t.metzger at intel dot com

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
Likewise for gdb.btrace/non-stop.exp

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
This is without libipt:
...
configure:25703: checking for libipt
configure:25722: gcc -o conftest -O0 -g -O0 -g  -Wall       conftest.c
-lncursesw -lm -ldl  -lipt >&5
conftest.c:178:10: fatal error: intel-pt.h: No such file or directory
  ...
configure:25732: result: no
configure:25759: WARNING: libipt is missing or unusable; some features may be
unavailable.
...

With libipt (using latest release v2.0.5) the two test-cases pass.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
https://sourceware.org/pipermail/gdb-patches/2023-February/197036.html

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #4 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #3)
> https://sourceware.org/pipermail/gdb-patches/2023-February/197036.html

As per this reply (
https://sourceware.org/pipermail/gdb-patches/2023-February/197039.html ), this
issue is different from PR30075, and is currently being investigated.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[markus.t.metzger at intel dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #5 from Markus Metzger <markus.t.metzger at intel dot com> ---
On my system, I do not get any BTS records on E-cores, and the perf event head
pointer does not move.  Looks like the BTS enable request gets stuck.

Could you print the result of 'maint btrace packet-history 0, +100'?

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #6 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Markus Metzger from comment #5)
> On my system, I do not get any BTS records on E-cores, and the perf event
> head pointer does not move.  Looks like the BTS enable request gets stuck.
> 
> Could you print the result of 'maint btrace packet-history 0, +100'?

I've build without libipt, ran the test-case gdb.btrace/exception.exp, copied
outputs/gdb.btrace/exception/gdb.in.2 to gdb.in, edited it like so:
...
$ cat gdb.in
set height 0
set width 0
dir
dir /data/vries/gdb/src/gdb/testsuite/gdb.btrace
file
/data/vries/gdb/leap-15-4/build/gdb/testsuite/outputs/gdb.btrace/exception/exception
delete breakpoints
info breakpoints
break -qualified main
run 
set record function-call-history-size 0
break 56
break 59
continue
set record btrace bts buffer-size 128000
record btrace
continue
maint btrace packet-history 0, +100
#record function-call-history 1
#record function-call-history /c 1
...
and ran it:
...
$ gdb -q -batch -ex "set trace-commands on" -x gdb.in
+set height 0
+set width 0
+dir
+dir /data/vries/gdb/src/gdb/testsuite/gdb.btrace
+file
/data/vries/gdb/leap-15-4/build/gdb/testsuite/outputs/gdb.btrace/exception/exception
+delete breakpoints
+info breakpoints
No breakpoints or watchpoints.
+break -qualified main
Breakpoint 1 at 0x400768: file
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc, line 55.
+run 

Breakpoint 1, main () at
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc:55
55        test ();
+set record function-call-history-size 0
+break 56
Breakpoint 2 at 0x40076d: file
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc, line 56.
+break 59
Breakpoint 3 at 0x400779: file
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc, line 59.
+continue

Breakpoint 2, main () at
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc:56
56        test (); /* bp.1  */
+set record btrace bts buffer-size 128000
+record btrace
+target record-btrace
+target record-btrace
+continue

Breakpoint 3, main () at
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc:59
59        return ret; /* bp.2  */
+maint btrace packet-history 0, +100
No trace.
...

I hope that answers your question.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[markus.t.metzger at intel dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #7 from Markus Metzger <markus.t.metzger at intel dot com> ---
(In reply to Tom de Vries from comment #6)

> record btrace
> continue
> maint btrace packet-history 0, +100
> #record function-call-history 1
> #record function-call-history /c 1

The maintenance command doesn't fetch the trace itself.  We'd need some other
record command before it, e.g. 'info record' or one of the two commented-out
commands.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #8 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Markus Metzger from comment #7)
> (In reply to Tom de Vries from comment #6)
> 
> > record btrace
> > continue
> > maint btrace packet-history 0, +100
> > #record function-call-history 1
> > #record function-call-history /c 1
> 
> The maintenance command doesn't fetch the trace itself.  We'd need some
> other record command before it, e.g. 'info record' or one of the two
> commented-out commands.

With the two commented out commands added back, I have:
...
+continue

Breakpoint 3, main () at
/data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc:59
59        return ret; /* bp.2  */
+record function-call-history 1
1       main()
+record function-call-history /c 1
1       main()
+maint btrace packet-history 0, +100
0       begin: 0x40076d, end: 0x400779
...

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[markus.t.metzger at intel dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #9 from Markus Metzger <markus.t.metzger at intel dot com> ---
(In reply to Tom de Vries from comment #8)
> (In reply to Markus Metzger from comment #7)
> > (In reply to Tom de Vries from comment #6)
> > 
> > > record btrace
> > > continue
> > > maint btrace packet-history 0, +100
> > > #record function-call-history 1
> > > #record function-call-history /c 1
> > 
> > The maintenance command doesn't fetch the trace itself.  We'd need some
> > other record command before it, e.g. 'info record' or one of the two
> > commented-out commands.
> 
> With the two commented out commands added back, I have:
> ...
> +continue
> 
> Breakpoint 3, main () at
> /data/vries/gdb/src/gdb/testsuite/gdb.btrace/exception.cc:59
> 59        return ret; /* bp.2  */
> +record function-call-history 1
> 1       main()
> +record function-call-history /c 1
> 1       main()
> +maint btrace packet-history 0, +100
> 0       begin: 0x40076d, end: 0x400779
> ...

Thanks.  Looks like you're not getting any BTS records, either.  The one entry
is the artificial record GDB adds to reach the current PC.

It looks like a kernel issue to me.  I'm discussing it with Intel kernel
developers.  This might take a bit of time.

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[Bug record/30073] [intel Efficient-core] FAIL: gdb.btrace/exception.exp: flat (pattern 1)

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=30073

--- Comment #10 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Markus Metzger from comment #9)
> It looks like a kernel issue to me.  I'm discussing it with Intel kernel
> developers.  This might take a bit of time.

Ack.  FTR, I'm running into this with:
- openSUSE Leap 15.4 using kernel version 5.14.21, and
- openSUSE Tumbleweed using kernel version 6.1.10.

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