Messages in this thread |  | | From | "Arayuru, Rajendra" <> | Subject | schedule_delayed_work off by one jiffy | Date | Fri, 17 Nov 2017 11:35:25 +0000 |
| |
Hi,
We are using Kernel 4.10.0-19-generic. In one of our test drivers, we assign a task to the global work queue, using schedule_delayed_work().
The issue we observe, is that when we call schedule_delayed_work(task, n) with delay of "n" jiffies, the task is getting scheduled after a delay of "n+1" and not "n" jiffies as expected.
This worked fine till the kernel version 4.4.0-87-generic. The observation is on kernel 4.10.0-19-generic and above.
A sample test code to highlight the difference between the kernel is given below:
static struct tq_struct g_Task = { routine:interrupt_handler, data:NULL };
static void interrupt_handler( struct work_struct *irrelevant ) { printk("check 1 Jiffies: %llu \n", get_jiffies_64()); schedule_delayed_work( &g_Task, 1); printk("Check 2 Jiffies: %llu \n", get_jiffies_64()); }
The dmesg output on 4.10 is as below (diff of 2 jiffies) [ 1047.975259] check 1 Jiffies: 4295153276 [ 1047.975263] Check 2 Jiffies: 4295153276 [ 1047.983255] check 1 Jiffies: 4295153278 [ 1047.983259] Check 2 Jiffies: 4295153278 [ 1047.991255] check 1 Jiffies: 4295153280 [ 1047.991260] Check 2 Jiffies: 4295153280
The dmesg output on 4.4 is as below (diff of 1 jiffies) [ 830.490657] check 1 Jiffies: 4295098955 [ 830.490664] Check 2 Jiffies: 4295098955 [ 830.494657] check 1 Jiffies: 4295098956 [ 830.494667] Check 2 Jiffies: 4295098956 [ 830.498656] check 1 Jiffies: 4295098957 [ 830.498663] Check 2 Jiffies: 4295098957
Thanks, Rajendra
|  |