Hi,
I read from ULK about the value of "TASKLET_STATE_RUN" for tasklet:
==
TASKLET_STATE_RUN
When set, this indicates that the tasklet is being executed; on a
uniprocessor system this flag is not used because there is no need to check
whether a specific tasklet is running.
In multiprocessor systems, checks the TASKLET_STATE_RUN flag of the tasklet.
-
If it is set, a tasklet of the same type is already running on another
CPU, so the function reinserts the task descriptor in the list pointed to by
tasklet_vec[n] or tasklet_hi_vec[n] and activates the TASKLET_SOFTIRQ or
HI_SOFTIRQ softirq again. In this way, execution of the tasklet is
deferred until no other tasklets of the same type are running on other CPUs.
==
Each tasklet is defined as a tasklet_struct which is linked into perCPU list
"tasklet_vec[NR_CPUS]".
My question is: One tasklet is “attached” to ONE CPU(since one tasklet is
put into ONE perCPU tasklet_struct list). And looks tasklet_action() only
handle tasklet_struct list of local CPU. So how could there be a chance for
this tasklet to be executed at another CPU? ?
299 struct tasklet_struct
300 {
301 struct tasklet_struct *next;
302 unsigned long state; // tasklet state sched/run
303 atomic_t count; //lock
304 void (*func)(unsigned long);
305 unsigned long data;
306 };
Puzzling,
Simon
