Hi Santosh, On Mon, Aug 1, 2011 at 6:54 AM, santhosh kumars <karuna.linux@xxxxxxxxx> wrote: > On Sat, Jul 30, 2011 at 10:45 PM, Dave Hylands <dhylands@xxxxxxxxx> wrote: >> Hi Santosh, >> >> On Sat, Jul 30, 2011 at 5:24 AM, santhosh kumars <karuna.linux@xxxxxxxxx> wrote: >>> Hi All, >>> I took following lines from robert love linux kernel development. >>> " If you need a schedulable entity to perform your bottom-half >>> processing, you need >>> work queues.They are the only bottom-half mechanisms that run in >>> process context, and >>> thus, the only ones that can sleep.This means they are useful for >>> situations in which you >>> need to allocate a lot of memory, obtain a semaphore, or perform block >>> I/O. If you do >>> not need a kernel thread to handle your deferred work, consider a >>> tasklet instead ." >>> >>> Here some times tasklets also runs in kernel thread context(by >>> ksoftirqd/n).So I want to know >>> what is the exact difference between workqueue and tasklet. >> >> A tasklet is something that in some OSes, might be called a software >> IRQ. It runs with interrupts enabled, but context switches are >> disabled. They are normally associated with device drivers where there >> is some extended processing that needs to be done, but perhaps not >> from an interrupt handler. >> http://www.xml.com/ldd/chapter/book/ch09.html#t5 >> >> The workqueues are documented here: >> http://lwn.net/Articles/11360/ >> Items in a workqueue are executed from a thread context (whereas >> tasklets are sort of half way between interrupt context and thread >> context). You can't perform blocking operations from a tasklet, > so we can conclude like tasklets some times runs in process > context(kthread context) > but that time contextswtiching is disabled. I think of them more as being interrupt context with interrupts enabled (since you still can't call blocking functions from a tasklet like you can from thread context). -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
