Messages in this thread | | | Date | Mon, 10 Jun 2013 05:25:43 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] kernel/softirq.c: delete 'while' looping to improve a little performance and beautify code |
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On Sun, Jun 09, 2013 at 08:30:19PM +0800, Chen Gang wrote: > > After finish the internal 'while', need not test TASKLET_STATE_SCHED > again, so looping back to outside 'while' is only for set_bit(). > > When use 'if' and set_bit() instead of 'while', it will save at least > one running conditional instruction, and also will be clearer for readers > (although the binary size will be a little bigger). > > The related patch is "1da177e Linux-2.6.12-rc2" > > > Signed-off-by: Chen Gang <gang.chen@asianux.com> > --- > kernel/softirq.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/kernel/softirq.c b/kernel/softirq.c > index a5f8836..52da25f 100644 > --- a/kernel/softirq.c > +++ b/kernel/softirq.c > @@ -540,10 +540,11 @@ void tasklet_kill(struct tasklet_struct *t) > if (in_interrupt()) > printk("Attempt to kill tasklet from interrupt\n"); > > - while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { > + if (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { > do { > yield(); > } while (test_bit(TASKLET_STATE_SCHED, &t->state)); > + set_bit(TASKLET_STATE_SCHED, &t->state);
This replaces an atomic test-and-set with two operations, a test and a set. Is this safe?
Thanx, Paul
> } > tasklet_unlock_wait(t); > clear_bit(TASKLET_STATE_SCHED, &t->state); > -- > 1.7.7.6 >
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