Dear list,
I'm running custom Fedora 17 Kernel
3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64, and the warning was shown on
dmesg:
[ 858.634304]
[ 858.634324] ===============================
[ 858.634350] [ INFO: suspicious RCU usage. ]
[ 858.634375] 3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64 #1 Not tainted
[ 858.634409] -------------------------------
[ 858.634435] kernel/pid.c:425 find_task_by_pid_ns() needs
rcu_read_lock() protection!
[ 858.634478]
[ 858.634479] other info that might help us debug this:
[ 858.634480]
[ 858.634528]
[ 858.634529] rcu_scheduler_active = 1, debug_locks = 0
[ 858.634567] no locks held by monitor/10550.
[ 858.634591]
[ 858.634592] stack backtrace:
[ 858.634620] Pid: 10550, comm: monitor Not tainted
3.3.0-0.rc5.git3.1.yfkm2.fc17.x86_64 #1
[ 858.634666] Call Trace:
[ 858.634688] [<ffffffff810c8c55>] lockdep_rcu_suspicious+0xe5/0x100
[ 858.634727] [<ffffffff81086921>] find_task_by_pid_ns+0x81/0xa0
[ 858.634762] [<ffffffff81086962>] find_task_by_vpid+0x22/0x30
[ 858.634798] [<ffffffff8131ccd5>] yfkm2_is_pid_running+0x15/0x40
[ 858.634835] [<ffffffff8131ce54>] sys_yfkm2_monitor+0x14/0x80
[ 858.634870] [<ffffffff816a6ba9>] system_call_fastpath+0x16/0x1b
monitor is user application that call sys_yfkm2_monitor syscall
passing a pid to it. The custom code worked as expected but I'm
curious with the warning message shown on dmesg. What am I doing
wrong?
The user application monitor.c:
...
#define SYS_yfkm2_monitor __NR_yfkm2_monitor
...
ret = syscall(SYS_yfkm2_monitor, pid);
...
The Kernel code yfkm2.c:
...
struct yfkm2 {
pid_t monitor; /* PID to monitor */
pid_t notifyme; /* PID to notify */
struct list_head list; /* Linked List struct */
};
...
/* Define and initialize yfkm2_(linked)list */
LIST_HEAD(yfkm2_list);
...
/* Define and initialize yfkm2_(read&write)lock */
DEFINE_RWLOCK(yfkm2_lock);
...
/*
* asmlinkage long sys_yfkm2_monitor(pid_t monitor)
*
* The system call that check if monitor correspond to a running pid and stores
* monitor at yfkm2_list->monitor
*
* return 0 if pid is running
* return 1 if pid is not running
*/
asmlinkage long sys_yfkm2_monitor(pid_t monitor)
{
struct yfkm2 *yfkm2_tmp;
if (yfkm2_is_pid_running(monitor) == 0) {
yfkm2_tmp = kmalloc(sizeof(*yfkm2_tmp), GFP_KERNEL);
yfkm2_tmp->monitor = monitor;
yfkm2_tmp->notifyme = 0;
write_lock(&yfkm2_lock);
list_add(&yfkm2_tmp->list, &yfkm2_list);
write_unlock(&yfkm2_lock);
return 0;
}
return 1;
}
...
/*
* yfkm2_is_pid_running(pid_t pid)
*
* Check if pid is running
*
* return 0 if pid is running
* return 1 if pid is not running
*/
int yfkm2_is_pid_running(pid_t pid)
{
struct task_struct *q;
q = find_task_by_vpid(pid);
if (q != NULL && q->pid == pid)
return 0;
return 1;
}
Thank you!
Peter
--
Peter Senna Tschudin
peter.senna@xxxxxxxxx
gpg id: 48274C36
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@xxxxxxxxxxxxxxxxx
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
