So, could you describe me exactly the procedure you are following wich
allows to reproduce this issue?
My attempt to run cond-torture-posix step by step:
1. copy cond-torture-posix as it was built in the blackfin-linux-dist (FDPIC)
to target
/opt/uClinux/blackfin-linux-dist/user/xenomai/build-xenomai-2.5.5.2/src/testsuite/unit/.libs/cond-torture-posix
2. first attempt to start cond-torture-posix fails because librt.so.0 was not
on my target, so I transferred
/opt/uClinux/bfin-linux-uclibc/bfin-linux-uclibc/runtime/lib/librt.so.0
3. cond-torture-posix standalone passes
4. I start cond-torture-posix on the target with "gdbserver :2222
./cond-torture-posix"
5. I start bfin-linux-uclibc-gdb and issue the commands
file cond-torture-posix
target remote 10.0.10.9:2222
break main
cont
6. The result is a SEGV on the target as described in
https://mail.gna.org/public/xenomai-help/2010-12/msg00088.html - even before
breakpoint main() was reached and without backtrace in gdb.
/usr/bin # gdbserver :2222 ./cond-torture-posix
Process ./cond-torture-posix created; pid = 240
Listening on port 2222
Remote debugging from host 10.0.10.10
NULL pointer access
Deferred Exception context
CURRENT PROCESS:
COMM=cond-torture-po PID=240 CPU=0
TEXT = 0x01738000-0x0173e214 DATA = 0x016e6214-0x016e6610
BSS = 0x016e6610-0x016a0000 USER-STACK = 0x016bfe60
return address: [0x01726f10]; contents of:
0x01726ef0: e42f 0015 0c07 1405 3047 67f8 e628 0015
0x01726f00: 320e 3044 300d 3014 e50a 003a 5ea2 9153
0x01726f10: [9159] ac5b 0061 0c07 1404 6000 e628 0015
0x01726f20: e801 0000 05a4 0010 e51a 0016 05f4 e800
ADSP-BF537-0.3 533(MHz CCLK) 133(MHz SCLK) (mpu off)
Linux version 2.6.34.7-ADI-2010R1-svn10663 (kawk@fee) (gcc version 4.3.5
(ADI-2010R1-RC4) ) #33 Wed Jan 12 10:02:14 CET 2011
SEQUENCER STATUS: Not tainted
SEQSTAT: 00060027 IPEND: 0008 IMASK: ffff SYSCFG: 0006
EXCAUSE : 0x27
physical IVG3 asserted : <0xffa0076c> { _trap + 0x0 }
RETE: <0x00000000> /* Maybe null pointer? */ RETN: <0x0161e000> /* kernel
dynamic memory */
RETX: <0x00000480> /* Maybe fixed code section */
RETS: <0x01726eda> [ /lib/libpthread.so.0 + 0x6eda ]
PC : <0x01726f10> [ /lib/libpthread.so.0 + 0x6f10 ]
DCPLB_FAULT_ADDR: <0x00000000> /* Maybe null pointer? */
...
What I'm actually doing to reproduce the EPERM from pthread_cond_wait in a
situation where I think it shouldn't occur was with the code I posted. Or,
keeping printfs() etc away from the tasks in which the pthread_cond_wait is
used, the code following at the end might be better suited to serve as an
example.
I'd be interested if this example gives the same output on Pierre Quelin's
system?
Explanation first - the core loop of each of three threads in the
example is as follows. It just sets bits in an errbits[] variable for each
thread depending on the result of pthread_cond_wait. The main task sleeps a
second, then sets run==0 and broadcasts on cond to stop all threads.
pthread_mutex_lock(&mutex);
while (run)
{
int r = pthread_cond_wait(&cond, &mutex);
loopcount[tnum]++;
switch(r)
{
case 0: errbits[tnum] |= LOG_NOERR; break;
case 1: errbits[tnum] |= LOG_EPERM; pthread_yield(); break;
default: errbits[tnum] |= LOG_OTHER; pthread_yield(); break;
}
}
pthread_mutex_unlock(&mutex);
Not sure if the pthread_yield() was necessary in this version of the code, it
might be a remainder of further experiments with varying priorities for the
threads.
I compile it with
bfin-linux-uclibc-gcc \
-I/opt/uClinux/blackfin-linux-dist/staging/usr/include \
-L/opt/uClinux/blackfin-linux-dist/staging/usr/lib \
-g -fPIC -fmessage-length=0 -mfast-fp -D_GNU_SOURCE -D_REENTRANT \
-D__XENO__
-Wl,@/opt/uClinux/blackfin-linux-dist/staging/usr/lib/posix.wrappers \
-lpthread_rt -lxenomai -o try try.c
Then transfer it to the target and run it standalone - the result is
# ./try
0 1x 0x0010
1 1x 0x0010
2 1x 0x0010
This result means that the loop body in each of three tasks was executed exactly
once and the result of pthread_cond_wait in the loop body was (always) zero (=>
the errbits are set to 0x0010, LOG_NOERR).
In contrast, I tried to run it via gdbserver. The commands were
set verbose on
set solib-absolute-prefix notexistent
set solib-search-path
/opt/uClinux/blackfin-linux-dist/staging/usr/lib:/opt/uClinux/bfin-linux-uclibc/bfin-linux-uclibc/runtime/lib
file try
target remote 10.0.10.9:2222
break main
cont
cont
The result on the target is now
/tmp # gdbserver :2222 ./try
Process ./try created; pid = 281
Listening on port 2222
Remote debugging from host 10.0.10.10
0 3784x 0x0001
1 6686x 0x0001
2 1x 0x0010
The 0x0001 (LOG_EPERM) shown for the first two threads means they always got
EPERM, never success.
By chance, I found that my example succeeds in all three threads (as without
gdbserver) on the target if I omit loading symbols with the "file" command in
gdb and just issue "target remote 10.0.10.9:2222" and "cont".
Here's the full code:
/* 2010-12-27 - test program for pthread_cond_wait */
#include <stdio.h>
#include <string.h>
#include <posix/pthread.h>
#define NUM_THREADS 3
#define LOG_EPERM 0x0001
#define LOG_OTHER 0x0008
#define LOG_NOERR 0x0010
volatile int run;
volatile unsigned errbits[NUM_THREADS];
volatile unsigned loopcount[NUM_THREADS];
pthread_cond_t cond;
pthread_mutex_t mutex;
const struct timespec dt = { 0, 100*1000 };
void* test_thread(void *cookie)
{
int tnum = *(int*)cookie;
pthread_mutex_lock(&mutex);
while (run)
{
int r = pthread_cond_wait(&cond, &mutex);
loopcount[tnum]++;
switch(r)
{
case 0: errbits[tnum] |= LOG_NOERR; break;
case 1: errbits[tnum] |= LOG_EPERM; pthread_yield(); break;
default: errbits[tnum] |= LOG_OTHER; pthread_yield(); break;
}
}
pthread_mutex_unlock(&mutex);
return NULL;
}
int main (void)
{
int r;
int i;
int tnum[NUM_THREADS];
pthread_t tid[NUM_THREADS];
run = 1;
r = pthread_cond_init(&cond, NULL); if (r!=0) printf("cond_init: %d\n", r);
r = pthread_mutex_init(&mutex, NULL); if (r!=0) printf("mutex_init: %d\n",
r);
pthread_attr_t attr;
r = pthread_attr_init(&attr);
if (r!=0) printf("attr_init: %d\n", r);
for (i=0; i<NUM_THREADS; i++)
{
tnum[i] = i;
errbits[i] = 0;
loopcount[i] = 0;
r = pthread_create(&(tid[i]), &attr, test_thread, &(tnum[i]));
if (r!=0) printf("create[%d]: %d\n", i, r);
}
sleep(1);
run = 0;
r = pthread_cond_broadcast(&cond);
if (r!=0) printf("cond_broadcast: %d\n", r);
for (i=0; i<NUM_THREADS; i++)
{
void *rp;
r = pthread_join(tid[i], &rp);
if (r!=0) printf("join[%d]: %d\n", i, r);
}
for (i=0; i<NUM_THREADS; i++)
{
printf("%d %dx 0x%04X\n", i, loopcount[i], errbits[i]);
}
return r;
}
Kolja
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