Hello,
I am trying to implement a device driver here. The read fop of my
driver sleeps itself untill the data is available. Here is the
relevent code:
static ssize_t ict3k5_read (struct file *filep, char *buff,
size_t count, loff_t *offp)
{
DECLARE_WAITQUEUE (wait, current);
ssize_t retval;
ssize_t i = 0;
add_wait_queue (&port_data_wait, &wait);
current->state = TASK_INTERRUPTIBLE;
do {
spin_lock_irq (&port_data_lock);
/* code to get the data from the queue
delived by an interrupt handler */
spin_unlock_irq (&port_data_lock);
if (i >= count) {
break;
}
if (filep->f_flags & O_NONBLOCK) {
retval = -EAGAIN;
break;
}
if (signal_pending (current)) {
retval = -ERESTARTSYS;
break;
}
schedule ();
} while (1);
current->state = TASK_RUNNING;
remove_wait_queue (&port_data_wait, &wait);
if (retval >= 0) {
retval = count;
}
return retval;
}
This works perfect when called from the user-space. Now i wanted to
utilize read in my ioctl fop. But when i call read from my ioctl, i
get this error:
Debug: sleeping function called from invalid context at
include/linux/rwsem.h:43in_atomic():0, irqs_disabled():1
[<0211691d>] __might_sleep+0x80/0x8a
[<0213f071>] rw_vm+0x85/0x1ea
[<02115617>] recalc_task_prio+0x141/0x14c
[<02115e97>] default_wake_function+0x0/0xc
[<0213f423>] put_user_size+0x29/0x2d
[<02115e97>] default_wake_function+0x0/0xc
[<129cf14a>] ict3k5_read+0xaa/0x1a0 [ict3k5]
[<02115e97>] default_wake_function+0x0/0xc
[<02115e97>] default_wake_function+0x0/0xc
[<021479f9>] chrdev_open+0xfa/0x127
[<129cf3da>] ict3k5_ioctl+0x8a/0x200 [ict3k5]
[<129cc0f1>] card_reader_ioctl+0x41/0x60 [card_reader_driver]
[<0214ea0e>] sys_ioctl+0x1f2/0x224
Can anyone tell me what I am doing wrong? Am I not allowed to sleep
inside ioctl? Thanks in advance.
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