Coredumps from programs with more than one thread show garbage
information for all threads except the primary. The problem was
introduced with:
http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5df240826c90afdc7956f55a004ea6b702df9203
on Apr 16 ("fix crash in entry.S restore_all") and is still present in
current builds.
"kill -SEGV" this program and "info threads" the resulting corefile to
see the problem:
#include <pthread.h>
static void* thread_sleep(void* x) { while (1) sleep(30); }
int main(int c, char** v) {
const static int tcount = 5;
pthread_t thr[tcount];
int i;
for (i=0; i<tcount; ++i)
pthread_create(&thr[i], NULL, thread_sleep, NULL);
while (1)
sleep(30);
return 0;
}
(gdb) info threads
7 process 18138 0x00000246 in ?? ()
6 process 18139 0x00000246 in ?? ()
5 process 18140 0x00000246 in ?? ()
4 process 18141 0x00000246 in ?? ()
3 process 18142 0x00000246 in ?? ()
2 process 18143 0x00000246 in ?? ()
* 1 process 18137 0xb7e69db6 in nanosleep () from /lib/tls/libc.so.6
(gdb)
All these threads should show a legitimate location (the same spot in
nanosleep) and do on kernels prior to the commit named above. (Notice
one too many threads listed here also -- is this a related problem?)
Commenting out this line (in asm/i386/kernel/process.c:copy_thread)
fixes the corefiles:
childregs = (struct pt_regs *) ((unsigned long) childregs - 8);
but presumably re-introduces the crash the original patch was intended
to fix. Should this line be conditioned somehow? Or do the corefile
write routines need to know about this adjusted offset?
Steve Work
Steve Work <[email protected]> wrote:
>
> Coredumps from programs with more than one thread show garbage
> information for all threads except the primary. The problem was
> introduced with:
>
> http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5df240826c90afdc7956f55a004ea6b702df9203
>
> on Apr 16 ("fix crash in entry.S restore_all") and is still present in
> current builds.
Thanks for working that out.
> "kill -SEGV" this program and "info threads" the resulting corefile to
> see the problem:
>
> #include <pthread.h>
> static void* thread_sleep(void* x) { while (1) sleep(30); }
> int main(int c, char** v) {
> const static int tcount = 5;
> pthread_t thr[tcount];
> int i;
> for (i=0; i<tcount; ++i)
> pthread_create(&thr[i], NULL, thread_sleep, NULL);
> while (1)
> sleep(30);
> return 0;
> }
>
> (gdb) info threads
> 7 process 18138 0x00000246 in ?? ()
> 6 process 18139 0x00000246 in ?? ()
> 5 process 18140 0x00000246 in ?? ()
> 4 process 18141 0x00000246 in ?? ()
> 3 process 18142 0x00000246 in ?? ()
> 2 process 18143 0x00000246 in ?? ()
> * 1 process 18137 0xb7e69db6 in nanosleep () from /lib/tls/libc.so.6
> (gdb)
>
> All these threads should show a legitimate location (the same spot in
> nanosleep) and do on kernels prior to the commit named above. (Notice
> one too many threads listed here also -- is this a related problem?)
>
> Commenting out this line (in asm/i386/kernel/process.c:copy_thread)
> fixes the corefiles:
>
> childregs = (struct pt_regs *) ((unsigned long) childregs - 8);
>
> but presumably re-introduces the crash the original patch was intended
> to fix. Should this line be conditioned somehow? Or do the corefile
> write routines need to know about this adjusted offset?
>
Yes, I guess fixing up the core output would be the way to fix it.
Hi Steve,
please open a bug at http://bugzilla.kernel.org/ for this issue so that
it doesn't get lost.
@Stas:
It was your patch that broke it, can you look into it?
TIA
Adrian
On Wed, Dec 07, 2005 at 10:52:52PM -0800, Steve Work wrote:
> Coredumps from programs with more than one thread show garbage
> information for all threads except the primary. The problem was
> introduced with:
>
> http://kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5df240826c90afdc7956f55a004ea6b702df9203
>
> on Apr 16 ("fix crash in entry.S restore_all") and is still present in
> current builds.
>
> "kill -SEGV" this program and "info threads" the resulting corefile to
> see the problem:
>
> #include <pthread.h>
> static void* thread_sleep(void* x) { while (1) sleep(30); }
> int main(int c, char** v) {
> const static int tcount = 5;
> pthread_t thr[tcount];
> int i;
> for (i=0; i<tcount; ++i)
> pthread_create(&thr[i], NULL, thread_sleep, NULL);
> while (1)
> sleep(30);
> return 0;
> }
>
> (gdb) info threads
> 7 process 18138 0x00000246 in ?? ()
> 6 process 18139 0x00000246 in ?? ()
> 5 process 18140 0x00000246 in ?? ()
> 4 process 18141 0x00000246 in ?? ()
> 3 process 18142 0x00000246 in ?? ()
> 2 process 18143 0x00000246 in ?? ()
> * 1 process 18137 0xb7e69db6 in nanosleep () from /lib/tls/libc.so.6
> (gdb)
>
> All these threads should show a legitimate location (the same spot in
> nanosleep) and do on kernels prior to the commit named above. (Notice
> one too many threads listed here also -- is this a related problem?)
>
> Commenting out this line (in asm/i386/kernel/process.c:copy_thread)
> fixes the corefiles:
>
> childregs = (struct pt_regs *) ((unsigned long) childregs - 8);
>
> but presumably re-introduces the crash the original patch was intended
> to fix. Should this line be conditioned somehow? Or do the corefile
> write routines need to know about this adjusted offset?
>
> Steve Work
Hi.
Adrian Bunk wrote:
> On Wed, Dec 07, 2005 at 10:52:52PM -0800, Steve Work wrote:
>> Or do the corefile
>> write routines need to know about this adjusted offset?
I think so, the attached patch seem to help.
Happy new year and happy hacking!
-----
teach dump_task_regs() about the -8 offset.
Signed-off-by: [email protected]