Hi Guys, I am Abhinav, new to this mailing list. Have some query on tasklet. Going Jerry Cooperstein's LDD book chapter-20 (Interrupt handling and deferrable functions) lab exercises. Attached is the snapshot of problem-2,3. I am referring here to only tasklet. Solution to problem for tasklet provided is below. ------------------------------------------------------------ -------------------------------- static void t_fun(unsigned long t_arg) { struct my_dat *data = (struct my_dat *)t_arg; atomic_inc(&counter_bh); pr_info( "In BH: counter_th = %d, counter_bh = %d, jiffies=%ld, %ld\n", atomic_read(&counter_th), atomic_read(&counter_bh), data->jiffies, jiffies); } static DECLARE_TASKLET(t_name, t_fun, (unsigned long)&my_data); /* initialize tasklet */ static irqreturn_t my_interrupt(int irq, void *dev_id) { struct my_dat *data = (struct my_dat *)dev_id; atomic_inc(&counter_th); data->jiffies = jiffies; tasklet_schedule(&t_name); mdelay(delay); /* hoke up a delay to try to cause pileup */ return IRQ_NONE; /* we return IRQ_NONE because we are just observing */ } module_init(my_generic_init); module_exit(my_generic_exit); ------------------------------------------------------------ ------------------------------------- Above solution will miss some bottom halves. To solve this problem, a solution is provided using dynamically allocated tasklet as below ------------------------------------------------------------------------- static void t_fun(unsigned long t_arg) { struct my_dat *data = (struct my_dat *)t_arg; atomic_inc(&counter_bh); pr_info("In BH: counter_th = %d, counter_bh = %d, jiffies=%ld, %ld\n", atomic_read(&counter_th), atomic_read(&counter_bh), data->jiffies, jiffies); kfree(data); } static irqreturn_t my_interrupt(int irq, void *dev_id) { struct tasklet_struct *t; struct my_dat *data; data = (struct my_dat *)kmalloc(sizeof(struct my_dat), GFP_ATOMIC); t = &data->tsk; data->jiffies = jiffies; tasklet_init(t, t_fun, (unsigned long)data); atomic_inc(&counter_th); tasklet_schedule(t); mdelay(delay); /* hoke up a delay to try to cause pileup */ return IRQ_NONE; /* we return IRQ_NONE because we are just observing */ } module_init(my_generic_init); module_exit(my_generic_exit); ------------------------------------------------------------------------- Above solution will not miss any bottom halves. Can somebody explains me why above solution is working ? What is so special about dynamic tasklets ? BR,Abhinav
