On Tue, Nov 12, 2013 at 8:52 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
> On Mon, Nov 11, 2013 at 8:52 PM, Ian Lance Taylor <i...@google.com> wrote:
>> On Fri, Nov 8, 2013 at 1:10 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>>>
>>> panic: runtime error: invalid memory address or nil pointer dereference
>>> [signal 0xb code=0x1 addr=0x1c]
>
>>> FAIL: runtime/pprof
>>> gmake[2]: *** [runtime/pprof/check] Error 1
>>>
>>> This one is new, I have to look into it a bit deeper.
>>
>>
>> I don't know what is happening here. I can't recreate it. There was
>> a different problem that could arise in runtime/pprof, that was fixed
>> by a patch I submitted on Saturday
>> (http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01016.html). So it's
>> possible that this is fixed now.
>
> The failure is specific to !USING_SPLIT_STACK targets:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x200009e9280 (LWP 21478)]
> 0x000000012001e854 in syscall.Exitsyscall () at
> ../../../gcc-svn/trunk/libgo/runtime/proc.c:1986
> 1986 m->p->syscalltick++;
> (gdb) list
> 1981 #ifdef USING_SPLIT_STACK
> 1982 gp->gcstack = nil;
> 1983 #endif
> 1984 gp->gcnext_sp = nil;
> 1985 runtime_memclr(&gp->gcregs, sizeof gp->gcregs);
> 1986 m->p->syscalltick++;
> 1987 }
> 1988
> 1989 static bool
> 1990 exitsyscallfast(void)
> (gdb) p m
> $2 = <optimized out>
>
> The crash is at line 1986, but it is unclear if m or p are null.
It is p that is null.
Trying to add debug printf fixes the failure. Adding:
Index: proc.c
===================================================================
--- proc.c (revision 204684)
+++ proc.c (working copy)
@@ -1969,6 +1969,7 @@ runtime_exitsyscall(void)
m->locks--;
+ printf ("Testx %p\n", m->p);
// Call the scheduler.
runtime_mcall(exitsyscall0);
makes test to pass.
However, moving pritf after runtime_mcall shows that m->p can be null
after the call:
$ ./a.out
Testy 0xc21000f000
Testy (nil)
panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x1c]
goroutine 10 [running]:
syscall.Exitsyscall
../../../gcc-svn/trunk/libgo/runtime/proc.c:1987
pprof.profileWriter
/home/uros/gcc-build/alphaev68-unknown-linux-gnu/libgo/gotest5746/test/pprof.go:600
created by runtime_pprof.StartCPUProfile
/home/uros/gcc-build/alphaev68-unknown-linux-gnu/libgo/gotest5746/test/pprof.go:594
goroutine 1 [chan receive]:
testing.RunTests
../../../gcc-svn/trunk/libgo/go/testing/testing.go:470
testing.Main
../../../gcc-svn/trunk/libgo/go/testing/testing.go:401
main.main
/home/uros/gcc-build/alphaev68-unknown-linux-gnu/libgo/gotest5746/test/_testmain.go:34
goroutine 8 [chan receive]:
testing.tRunner
../../../gcc-svn/trunk/libgo/go/testing/testing.go:389
created by testing.RunTests
../../../gcc-svn/trunk/libgo/go/testing/testing.go:469
Trivial fix would be adding if (m->p) in front of the dereference, but
I don't know if exitsyscall0 is allowed to return nill in m->p.
Uros.
