Since possibleCycle is 0, it means that there is no possible TM deadlock
(2 is waiting on 1 but 1 is not waiting on 2).
However processor 1 might be doing something weird.
Can you determine what the remote thread is doing?
Could you disassemble the remote PC 0xf000613c and see what it
corresponds to?
Jayaram
Indraneel Mukherjee wrote:
Hi all,
I recently wrote a stresscode for logTM on simics-2.2.19 and
gems-2.0, on a 4 processor machine. The stresscode runs two threads
generating many conflicting transactions that would deadlock unless
one of the transactions aborts. On running it on logTM with the
XACT_CONFLICT_RES flag set to BASE or TIMESTAMP, however, conflicts
are detected but none of the transactions are aborted. As such the
code runs on indefinitely; a similar code that uses locks to replace
transactions by serialized access to the critical section runs in
about 20 minutes. Does anyone have any idea why logTM is not
aborting?The last few lines of debugging output looks like the
following when the stresscode is run for a long time:
1067372669 2 [2,0] TID 1 XACT NACK 0 by 1 [ 1, 0 ] NID: 0
[0x1a06f898, line 0x1a06f880] VA [0x0, line 0x0] PC [0x112ec, line
0x112c0] my_ts 1067372155 nack_ts 23405901 possible_cycle 0
1067372670 2 [2,0] CONFLICTING REQUEST [0x1a06f898, line 0x1a06f880]
possibleCycle: 0 shouldTrap: 0
1067373184 2 [2,0] RECEIVED NACK [0x1a06f898, line 0x1a06f880]
remote_id: 1 [1,0] myPC: [0x112ec, line 0x112c0] remotePC:
[0xf000613c, line 0xf0006100] local_timestamp: 1067372670
remote_timestamp: 23405901
1067373184 2 [2,0] TID 1 XACT NACK 0 by 1 [ 1, 0 ] NID: 0
[0x1a06f898, line 0x1a06f880] VA [0x0, line 0x0] PC [0x112ec, line
0x112c0] my_ts 1067372670 nack_ts 23405901 possible_cycle 0
1067373185 2 [2,0] CONFLICTING REQUEST [0x1a06f898, line 0x1a06f880]
possibleCycle: 0 shouldTrap: 0
1067373699 2 [2,0] RECEIVED NACK [0x1a06f898, line 0x1a06f880]
remote_id: 1 [1,0] myPC: [0x112ec, line 0x112c0] remotePC:
[0xf0031298, line 0xf0031280] local_timestamp: 1067373185
remote_timestamp: 23405901
1067373699 2 [2,0] TID 1 XACT NACK 0 by 1 [ 1, 0 ] NID: 0
[0x1a06f898, line 0x1a06f880] VA [0x0, line 0x0] PC [0x112ec, line
0x112c0] my_ts 1067373185 nack_ts 23405901 possible_cycle 0
1067373700 2 [2,0] CONFLICTING REQUEST [0x1a06f898, line 0x1a06f880]
possibleCycle: 0 shouldTrap: 0
1067374214 2 [2,0] RECEIVED NACK [0x1a06f898, line 0x1a06f880]
remote_id: 1 [1,0] myPC: [0x112ec, line 0x112c0] remotePC:
[0xf0031dec, line 0xf0031dc0] local_timestamp: 1067373700
remote_timestamp: 23405901
1067374214 2 [2,0] TID 1 XACT NACK 0 by 1 [ 1, 0 ] NID: 0
[0x1a06f898, line 0x1a06f880] VA [0x0, line 0x0] PC [0x112ec, line
0x112c0] my_ts 1067373700 nack_ts 23405901 possible_cycle 0
1067374215 2 [2,0] CONFLICTING REQUEST [0x1a06f898, line 0x1a06f880]
possibleCycle: 0 shouldTrap: 0
1067374729 2 [2,0] RECEIVED NACK [0x1a06f898, line 0x1a06f880]
remote_id: 1 [1,0] myPC: [0x112ec, line 0x112c0] remotePC:
[0xf00306c4, line 0xf00306c0] local_timestamp: 1067374215
remote_timestamp: 23405901
1067374729 2 [2,0] TID 1 XACT NACK 0 by 1 [ 1, 0 ] NID: 0
[0x1a06f898, line 0x1a06f880] VA [0x0, line 0x0] PC [0x112ec, line
0x112c0] my_ts 1067374215 nack_ts 23405901 possible_cycle 0
1067374730 2 [2,0] CONFLICTING REQUEST [0x1a06f898, line 0x1a06f880]
possibleCycle: 0 shouldTrap: 0
1067375244 2 [2,0] RECEIVED NACK [0x1a06f898, line 0x1a06f880]
remote_id: 1 [1,0] myPC: [0x112ec, line 0x112c0] remotePC:
[0xf0030eb0, line 0xf0030e80] local_timestamp: 1067374730
remote_timestamp: 23405901
In short, the same thread keeps receiving NACKs within a transaction
and never proceeds.
I'm also including my stresscode, just in case:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include <pthread.h>
#include "transaction.h"
#define MAGIC_BREAK do { \
__asm__ __volatile__ ("sethi 0x40000, %g0"); \
} while (0);
#define ARR_SIZE 1000000
int num_loops;
int arr_size;
int reps;
int array[ARR_SIZE];
void* slaveStart(void *id){
int myid;
int tmp;
int i,j,k;
int local_sense = 0;
int dummy;
myid = *((int*)id);
tm_bind_to_cabinet(myid+1);
Barrier_breaking(&local_sense, myid, 2);
set_transaction_registers(myid);
/* warm-up caches */
for (i=0; i<arr_size; ++i)
dummy = array[i];
for (i=0; i<num_loops; ++i){
BEGIN_WORKLOAD_TRANSACTION
BEGIN_TRANSACTION(0)
if (myid == 0)
for (j=0;j<arr_size;++j)
for (k=0;k<reps;++k)
++array[j];
else
for (j=arr_size-1;j>=0;--j)
for (k=0;k<reps;++k)
--array[j];
COMMIT_TRANSACTION(0)
END_WORKLOAD_TRANSACTION
}
Barrier_breaking(&local_sense, myid, 2);
}
int main(int argc, char **argv){
int i;
pthread_t threads[2];
pthread_attr_t pthread_custom_attr;
int id[2] = {0,1};
if (argc < 4) {
fprintf (stderr, "./aborter loop-size array-size reps");
return (1);
}
num_loops = atoi(argv[1]);
arr_size = atoi(argv[2]);
reps = atoi(argv[3]);
// init array
for (i=0; i<ARR_SIZE; ++i)
array[i] = 0;
init_transaction_state(2); // #threads = 2
MAGIC_BREAK ;
pthread_attr_init(&pthread_custom_attr); // get default attributes
pthread_create(&threads[0], &pthread_custom_attr, slaveStart,
(void*)&id[0]);
pthread_create(&threads[1], &pthread_custom_attr, slaveStart,
(void*)&id[1]);
// Synchronize on termination
pthread_join(threads[0],NULL);
pthread_join(threads[1],NULL);
MAGIC_BREAK ;
return (0);
}
------------------------------------------------------------------------
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