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authorJoe Perches <joe@perches.com>2014-01-27 20:07:14 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-28 00:02:40 -0500
commit2e702b9f6cba4eb87d90e2a2d425a1fc05eec803 (patch)
treeade4a3bcec477ced2780f1841e7c06f547effe84 /kernel/softirq.c
parenta19428e5c3f4f39c302cb97b847dfd23613145c1 (diff)
softirq: use ffs() in __do_softirq()
Possible speed improvement of __do_softirq() by using ffs() instead of using a while loop with an & 1 test then single bit shift. Signed-off-by: Joe Perches <joe@perches.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/softirq.c')
-rw-r--r--kernel/softirq.c43
1 files changed, 22 insertions, 21 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8a1e6e104892..ba79bbfe380e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -229,6 +229,7 @@ asmlinkage void __do_softirq(void)
229 struct softirq_action *h; 229 struct softirq_action *h;
230 bool in_hardirq; 230 bool in_hardirq;
231 __u32 pending; 231 __u32 pending;
232 int softirq_bit;
232 int cpu; 233 int cpu;
233 234
234 /* 235 /*
@@ -253,30 +254,30 @@ restart:
253 254
254 h = softirq_vec; 255 h = softirq_vec;
255 256
256 do { 257 while ((softirq_bit = ffs(pending))) {
257 if (pending & 1) { 258 unsigned int vec_nr;
258 unsigned int vec_nr = h - softirq_vec; 259 int prev_count;
259 int prev_count = preempt_count(); 260
260 261 h += softirq_bit - 1;
261 kstat_incr_softirqs_this_cpu(vec_nr); 262
262 263 vec_nr = h - softirq_vec;
263 trace_softirq_entry(vec_nr); 264 prev_count = preempt_count();
264 h->action(h);
265 trace_softirq_exit(vec_nr);
266 if (unlikely(prev_count != preempt_count())) {
267 printk(KERN_ERR "huh, entered softirq %u %s %p"
268 "with preempt_count %08x,"
269 " exited with %08x?\n", vec_nr,
270 softirq_to_name[vec_nr], h->action,
271 prev_count, preempt_count());
272 preempt_count_set(prev_count);
273 }
274 265
275 rcu_bh_qs(cpu); 266 kstat_incr_softirqs_this_cpu(vec_nr);
267
268 trace_softirq_entry(vec_nr);
269 h->action(h);
270 trace_softirq_exit(vec_nr);
271 if (unlikely(prev_count != preempt_count())) {
272 printk(KERN_ERR "huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
273 vec_nr, softirq_to_name[vec_nr], h->action,
274 prev_count, preempt_count());
275 preempt_count_set(prev_count);
276 } 276 }
277 rcu_bh_qs(cpu);
277 h++; 278 h++;
278 pending >>= 1; 279 pending >>= softirq_bit;
279 } while (pending); 280 }
280 281
281 local_irq_disable(); 282 local_irq_disable();
282 283