: Fix PR19061, gdb hangs/spins-on-cpu when debugging any program on Alpha
Commit Message
Hello!
Attached patch fixes PR19061, where gdb hangs/spins-on-cpu when
debugging any program on Alpha. The patch is effectively a forward
port of Richard's patch from the Comment #5 of the PR [1].
2017-12-15 Uros Bizjak <ubizjak@gmail.com>
Richard Henderson <rth@redhat.com>
PR gdb/19061
* alpha-tdep.c (alpha_software_single_step): Call
alpha_deal_with_atomic_sequence here.
(set_gdbarch_software_single_step): Set to alpha_software_single_step.
* nat/linux-ptrace.h [__alpha__]: Define GDB_ARCH_IS_TRAP_BRKPT
and GDB_ARCH_IS_TRAP_HWBKPT.
Patch was tested on alphaev68-linux-gnu, also tested with gcc's
testsuite, where it fixed all hangs in guality.exp and
simulate-thread.exp testcases.
Please note that I have no commit access, so if approved, please
commit the patch to the source repository for me. I also have
functionally equivalent patch for gdb-8 branch which I plan to submit
later.
[1] https://sourceware.org/bugzilla/show_bug.cgi?id=19061#c5
Uros.
Comments
On 12/15/2017 12:11 PM, Uros Bizjak wrote:
>
> Please note that I have no commit access, so if approved, please
> commit the patch to the source repository for me.
Merged.
Thanks,
Pedro Alves
On 2017-12-15 07:11 AM, Uros Bizjak wrote:
> Hello!
>
> Attached patch fixes PR19061, where gdb hangs/spins-on-cpu when
> debugging any program on Alpha. The patch is effectively a forward
> port of Richard's patch from the Comment #5 of the PR [1].
>
>
> 2017-12-15 Uros Bizjak <ubizjak@gmail.com>
> Richard Henderson <rth@redhat.com>
>
> PR gdb/19061
> * alpha-tdep.c (alpha_software_single_step): Call
> alpha_deal_with_atomic_sequence here.
> (set_gdbarch_software_single_step): Set to alpha_software_single_step.
> * nat/linux-ptrace.h [__alpha__]: Define GDB_ARCH_IS_TRAP_BRKPT
> and GDB_ARCH_IS_TRAP_HWBKPT.
>
> Patch was tested on alphaev68-linux-gnu, also tested with gcc's
> testsuite, where it fixed all hangs in guality.exp and
> simulate-thread.exp testcases.
>
> Please note that I have no commit access, so if approved, please
> commit the patch to the source repository for me. I also have
> functionally equivalent patch for gdb-8 branch which I plan to submit
> later.
>
> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=19061#c5
>
> Uros.
>
Hi Uros and Richard,
I would need your input. Using this cross-compiler:
alphaev67-unknown-linux-gnu-gcc (crosstool-NG crosstool-ng-1.22.0-677-ga3dd55b9) 6.3.0
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
I get this error:
CXX linux-nat.o
/home/simark/src/binutils-gdb/gdb/linux-nat.c: In function 'void save_stop_reason(lwp_info*)':
/home/simark/src/binutils-gdb/gdb/linux-nat.c:2718:9: error: duplicated 'if' condition [-Werror=duplicated-cond]
else if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
^~
In file included from /home/simark/src/binutils-gdb/gdb/linux-nat.c:31:0:
/home/simark/src/binutils-gdb/gdb/nat/linux-ptrace.h:173:41: note: previously used here
# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
~~~~~^~~~~~~~~~~~~~
/home/simark/src/binutils-gdb/gdb/linux-nat.c:2709:13: note: in expansion of macro 'GDB_ARCH_IS_TRAP_BRKPT'
else if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code))
^~~~~~~~~~~~~~~~~~~~~~
Does Alpha even have hardware breakpoints? If not, I would suggest
defining GDB_ARCH_IS_TRAP_HWBKPT to 0 for __alpha__. It would get
rid of the error, and be more exact (no si_code can mean "hardware
breakpoint" on alpha).
Simon
On Wed, May 30, 2018 at 4:53 PM, Simon Marchi <simon.marchi@ericsson.com> wrote:
> On 2017-12-15 07:11 AM, Uros Bizjak wrote:
>> Hello!
>>
>> Attached patch fixes PR19061, where gdb hangs/spins-on-cpu when
>> debugging any program on Alpha. The patch is effectively a forward
>> port of Richard's patch from the Comment #5 of the PR [1].
>>
>>
>> 2017-12-15 Uros Bizjak <ubizjak@gmail.com>
>> Richard Henderson <rth@redhat.com>
>>
>> PR gdb/19061
>> * alpha-tdep.c (alpha_software_single_step): Call
>> alpha_deal_with_atomic_sequence here.
>> (set_gdbarch_software_single_step): Set to alpha_software_single_step.
>> * nat/linux-ptrace.h [__alpha__]: Define GDB_ARCH_IS_TRAP_BRKPT
>> and GDB_ARCH_IS_TRAP_HWBKPT.
>>
>> Patch was tested on alphaev68-linux-gnu, also tested with gcc's
>> testsuite, where it fixed all hangs in guality.exp and
>> simulate-thread.exp testcases.
>>
>> Please note that I have no commit access, so if approved, please
>> commit the patch to the source repository for me. I also have
>> functionally equivalent patch for gdb-8 branch which I plan to submit
>> later.
>>
>> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=19061#c5
>>
>> Uros.
>>
>
> Hi Uros and Richard,
>
> I would need your input. Using this cross-compiler:
>
> alphaev67-unknown-linux-gnu-gcc (crosstool-NG crosstool-ng-1.22.0-677-ga3dd55b9) 6.3.0
> Copyright (C) 2016 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions. There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>
> I get this error:
>
> CXX linux-nat.o
> /home/simark/src/binutils-gdb/gdb/linux-nat.c: In function 'void save_stop_reason(lwp_info*)':
> /home/simark/src/binutils-gdb/gdb/linux-nat.c:2718:9: error: duplicated 'if' condition [-Werror=duplicated-cond]
> else if (GDB_ARCH_IS_TRAP_HWBKPT (siginfo.si_code))
> ^~
> In file included from /home/simark/src/binutils-gdb/gdb/linux-nat.c:31:0:
> /home/simark/src/binutils-gdb/gdb/nat/linux-ptrace.h:173:41: note: previously used here
> # define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
> ~~~~~^~~~~~~~~~~~~~
> /home/simark/src/binutils-gdb/gdb/linux-nat.c:2709:13: note: in expansion of macro 'GDB_ARCH_IS_TRAP_BRKPT'
> else if (GDB_ARCH_IS_TRAP_BRKPT (siginfo.si_code))
> ^~~~~~~~~~~~~~~~~~~~~~
>
> Does Alpha even have hardware breakpoints? If not, I would suggest
> defining GDB_ARCH_IS_TRAP_HWBKPT to 0 for __alpha__. It would get
> rid of the error, and be more exact (no si_code can mean "hardware
> breakpoint" on alpha).
Richard said that:
The hardware does not, but the linux kernel pretends.
IIRC the number of round-trips and flushes is supposed
to be lower doing it from within the kernel.
BR,
Uros.
On 2018-05-30 14:07, Uros Bizjak wrote:
> Richard said that:
>
> The hardware does not, but the linux kernel pretends.
> IIRC the number of round-trips and flushes is supposed
> to be lower doing it from within the kernel.
I don't really understand your response. The hardware does not have
hardware breakpoints, but the linux kernel pretends that it has? Are
you actually talking about single step?
Simon
@@ -767,10 +767,8 @@ static const int stq_c_opcode = 0x2f;
the sequence. */
static std::vector<CORE_ADDR>
-alpha_deal_with_atomic_sequence (struct regcache *regcache)
+alpha_deal_with_atomic_sequence (struct gdbarch *gdbarch, CORE_ADDR pc)
{
- struct gdbarch *gdbarch = regcache->arch ();
- CORE_ADDR pc = regcache_read_pc (regcache);
CORE_ADDR breaks[2] = {-1, -1};
CORE_ADDR loc = pc;
CORE_ADDR closing_insn; /* Instruction that closes the atomic sequence. */
@@ -1723,9 +1721,19 @@ alpha_next_pc (struct regcache *regcache, CORE_ADDR pc)
std::vector<CORE_ADDR>
alpha_software_single_step (struct regcache *regcache)
{
- CORE_ADDR pc = alpha_next_pc (regcache, regcache_read_pc (regcache));
+ struct gdbarch *gdbarch = regcache->arch ();
+ CORE_ADDR pc, next_pc;
+
+ pc = regcache_read_pc (regcache);
+ std::vector<CORE_ADDR> next_pcs
+ = alpha_deal_with_atomic_sequence (gdbarch, pc);
+
+ if (!next_pcs.empty ())
+ return next_pcs;
+
+ next_pc = alpha_next_pc (regcache, pc);
- return {pc};
+ return {next_pc};
}
@@ -1821,7 +1829,7 @@ alpha_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
set_gdbarch_cannot_step_breakpoint (gdbarch, 1);
/* Handles single stepping of atomic sequences. */
- set_gdbarch_software_single_step (gdbarch, alpha_deal_with_atomic_sequence);
+ set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
/* Hook in ABI-specific overrides, if they have been registered. */
gdbarch_init_osabi (info, gdbarch);
@@ -155,6 +155,8 @@ struct buffer;
Beginning with Linux 4.6, the MIPS port reports proper TRAP_BRKPT and
TRAP_HWBKPT codes, so we also match them.
+ The Alpha kernel uses TRAP_BRKPT for all traps.
+
The generic Linux target code should use GDB_ARCH_IS_TRAP_* instead
of TRAP_* to abstract out these peculiarities. */
#if defined __i386__ || defined __x86_64__
@@ -166,6 +168,9 @@ struct buffer;
#elif defined __mips__
# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == SI_KERNEL || (X) == TRAP_BRKPT)
# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == SI_KERNEL || (X) == TRAP_HWBKPT)
+#elif defined __alpha__
+# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
+# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_BRKPT)
#else
# define GDB_ARCH_IS_TRAP_BRKPT(X) ((X) == TRAP_BRKPT)
# define GDB_ARCH_IS_TRAP_HWBKPT(X) ((X) == TRAP_HWBKPT)