Dear, I am trying to debug a posix application and I noticed what I think is a bug in the method pthread_cond_wait (). it returns EPERM when the application is started with gdb. Could you please help me to understand what is wrong or locate the bug? Best regards. Pierre Quélin ------------------------------------ Configuration ------------------------------------ Ubuntu 10.10 Linux xenomai 2.6.35.7-core2xeon-adeos-2.8-00 #1 SMP PREEMPT Mon Dec 6 13:37:41 CET 2010 i686 GNU/Linux Gnu C 4.4.4-14ubuntu5) GNU gdb (GDB) 7.2-ubuntu Gnu make 3.81 util-linux ng 2.17.2) mount ng 2.17.2 (with libblkid and selinux support) module-init-tools 3.12 e2fsprogs 1.41.12 Linux C Library 2.12.1 Dynamic linker (ldd) 2.12.1 Procps 3.2.8 Net-tools 1.60 Kbd 1.15 Sh-utils 8.5 Modules Loaded ip6table_filter ip6_tables binfmt_misc ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ipt_REJECT xt_tcpudp iptable_filter ip_tables x_tables bridge stp kvm_intel kvm parport_pc ppdev arc4 rt73usb crc_itu_t rt2x00usb rt2x00lib led_class i3200_edac edac_core mac80211 lp psmouse serio_raw cfg80211 parport hed floppy e1000 e1000e ------------------------------------ Code ------------------------------------ #include /* line 0 */ #include void* bodyA(void*) { pthread_cond_t cond; pthread_mutex_t mutex; pthread_mutexattr_t attr; int res; res = pthread_mutexattr_init( &attr ); res = pthread_mutexattr_setprotocol( &attr, PTHREAD_PRIO_INHERIT ); res = pthread_mutex_init( &mutex, &attr ); res = pthread_mutexattr_destroy( &attr ); res = pthread_cond_init( &cond, NULL ); bool state = false; res = pthread_mutex_lock( &mutex ); while ( !state ) { res = pthread_cond_wait( &cond, &mutex ); if ( 0 != res ) { res = pthread_mutex_unlock( &mutex ); return (void*)-1; } else { (void)res; } } state = true; res = pthread_mutex_unlock( &mutex ); return 0; }; void* bodyB(void*) { pthread_cond_t cond; pthread_mutex_t mutex; pthread_mutexattr_t attr; int res; res = pthread_mutexattr_init( &attr ); res = pthread_mutexattr_setprotocol( &attr, PTHREAD_PRIO_INHERIT ); res = pthread_mutex_init( &mutex, &attr ); res = pthread_mutexattr_destroy( &attr ); res = pthread_cond_init( &cond, NULL ); bool state = false; res = pthread_mutex_lock( &mutex ); while ( !state ) { res = pthread_cond_wait( &cond, &mutex ); if ( 0 != res ) { res = pthread_mutex_unlock( &mutex ); return (void*)-1; } else { (void)res; } } state = true; res = pthread_mutex_unlock( &mutex ); return 0; }; #define DEFAULT_PRIORITY 100 #define HIGHEST_PRIORITY 2 #define LOWEST_PRIORITY 255 #define wind_normalized_prio(prio, sched_type) \ ({ int __p = sched_get_priority_min(sched_type) + ( ( ( LOWEST_PRIORITY - (prio) ) * ( sched_get_priority_max(sched_type) - sched_get_priority_min (sched_type) ) ) / LOWEST_PRIORITY ); __p; }) int main() { mlockall(MCL_CURRENT | MCL_FUTURE); struct sched_param parA; parA.sched_priority = wind_normalized_prio(DEFAULT_PRIORITY, SCHED_FIFO); pthread_t threadA; pthread_attr_t pthread_attrA; int res; res = pthread_attr_init(&pthread_attrA); res = pthread_attr_setinheritsched (&pthread_attrA, PTHREAD_EXPLICIT_SCHED); res = pthread_attr_setschedpolicy (&pthread_attrA, SCHED_FIFO); res = pthread_attr_setschedparam( &pthread_attrA, &parA ); res = pthread_create( &threadA, &pthread_attrA, bodyA, NULL ); #ifdef __XENO__ pthread_set_name_np( threadA, "threadA" ); #endif res = pthread_attr_destroy( &pthread_attrA ); struct sched_param parB; parB.sched_priority = wind_normalized_prio(DEFAULT_PRIORITY, SCHED_FIFO); pthread_t threadB; pthread_attr_t pthread_attrB; res = pthread_attr_init(&pthread_attrB); res = pthread_attr_setinheritsched (&pthread_attrB, PTHREAD_EXPLICIT_SCHED); res = pthread_attr_setschedpolicy (&pthread_attrB, SCHED_FIFO); pthread_attr_setschedparam( &pthread_attrB, &parB ); res = pthread_create( &threadB, &pthread_attrB, bodyB, NULL ); #ifdef __XENO__ pthread_set_name_np( threadB, "threadB" ); #endif res = pthread_attr_destroy( &pthread_attrB ); pthread_cond_t cond; pthread_mutex_t mutex; pthread_mutexattr_t attr; res = pthread_mutexattr_init( &attr ); res = pthread_mutexattr_setprotocol( &attr, PTHREAD_PRIO_INHERIT ); res = pthread_mutex_init( &mutex, &attr ); res = pthread_mutexattr_destroy( &attr ); res = pthread_cond_init( &cond, NULL ); bool state = false; res = pthread_mutex_lock( &mutex ); while ( !state ) { res = pthread_cond_wait( &cond, &mutex ); if ( 0 != res ) { res = pthread_mutex_unlock( &mutex ); return -1; } else { (void)res; } } state = true; res = pthread_mutex_unlock( &mutex ); return 0; } ------------------------------------ Linux without gdb : Ok ------------------------------------ ------------------------------------ Linux with gdb : Ok ------------------------------------ Thread [3] 5111 (Suspended : Container) __kernel_vsyscall() at 0xb7fe1424 pthread_cond_wait@domain.hid() at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:142 0xb7fbd4ad bodyB() at /home/generation/Projets/PosixTest/src/Main.cpp:55 0x8048af1 start_thread() at pthread_create.c:304 0xb7fb8cc9 clone() at ../sysdeps/unix/sysv/linux/i386/clone.S:130 0xb7e1469e Thread [2] 5110 (Suspended : Container) __kernel_vsyscall() at 0xb7fe1424 pthread_cond_wait@domain.hid() at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:142 0xb7fbd4ad bodyA() at /home/generation/Projets/PosixTest/src/Main.cpp:21 0x8048a01 start_thread() at pthread_create.c:304 0xb7fb8cc9 clone() at ../sysdeps/unix/sysv/linux/i386/clone.S:130 0xb7e1469e Thread [1] 5106 (Suspended : Signal : SIGINT:Interrupt) __kernel_vsyscall() at 0xb7fe1424 pthread_cond_wait@domain.hid() at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:142 0xb7fbd4ad main() at /home/generation/Projets/PosixTest/src/Main.cpp:131 0x8048dfa ------------------------------------ Xenomai without gdb : Ok ------------------------------------ generation@domain.hid$ cat /proc/xenomai/sched CPU PID CLASS PRI TIMEOUT TIMEBASE STAT NAME 0 0 idle -1 - master R ROOT/0 1 0 idle -1 - master R ROOT/1 0 5025 rt 0 - master W PosixTest 0 5026 rt 60 - master W threadA 0 5027 rt 60 - master W threadB ------------------------------------ Xenomai with gdb : Nok ------------------------------------ ->Step 1 : (break point on pthread_cond_wait) Thread [2] 5193 (Suspended : Breakpoint) bodyA() at /home/generation/Projets/PosixTest/src/Main.cpp:21 0x8048b0f 0xb7fc30b2 start_thread() at pthread_create.c:304 0xb7fa4cc9 clone() at ../sysdeps/unix/sysv/linux/i386/clone.S:130 0xb7df869e Thread [1] 5188 (Suspended : Container) __kernel_vsyscall() at 0xb7fe1424 mmap() at ../sysdeps/unix/sysv/linux/i386/mmap.S:62 0xb7df4a88 allocate_stack() at allocatestack.c:489 0xb7fa563b __pthread_create_2_1() at pthread_create.c:458 0xb7fa563b __real_pthread_create() at 0xb7fca382 __wrap_pthread_create() at 0xb7fc2e2f main() at /home/generation/Projets/PosixTest/src/Main.cpp:110 0x8048e7e ->Step 2 : break point after pthread_cond_wait. pthread_cond_wait retrun 1 (EPERM) Thread [3] 5204 (Suspended : Container) __kernel_vsyscall() at 0xb7fe1424 __lll_lock_wait_private() at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/lowlevellock.S:95 0xb7fac133 _L_lock_2466() at 0xb7fa5d2a start_thread() at pthread_create.c:295 0xb7fa4ec1 clone() at ../sysdeps/unix/sysv/linux/i386/clone.S:130 0xb7df869e Thread [2] 5193 (Suspended : Step) bodyA() at /home/generation/Projets/PosixTest/src/Main.cpp:22 0x8048b24 0xb7fc30b2 start_thread() at pthread_create.c:304 0xb7fa4cc9 clone() at ../sysdeps/unix/sysv/linux/i386/clone.S:130 0xb7df869e Thread [1] 5188 (Suspended : Container)