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authorCheng Xu <chengxu@linux.vnet.ibm.com>2011-05-14 02:20:02 -0400
committerIngo Molnar <mingo@elte.hu>2011-05-16 05:00:54 -0400
commitec514c487c3d4b652943da7b0afbc094eee08cfa (patch)
treed6766fd9a3f6eec2816a8191cf02f14564ba7473 /kernel/sched_rt.c
parentbd1a643e10eb8782b36b47c3602300319dd2fb00 (diff)
sched: Fix rt_rq runtime leakage bug
This patch is to fix the real-time scheduler bug reported at: https://lkml.org/lkml/2011/4/26/13 That is, when running multiple real-time threads on every logical CPUs and then turning off one CPU, the kernel will bug at function __disable_runtime(). Function __disable_runtime() bugs and reports leakage of rt_rq runtime. The root cause is __disable_runtime() assumes it iterates through all the existing rt_rq's while walking rq->leaf_rt_rq_list, which actually contains only runnable rt_rq's. This problem also applies to __enable_runtime() and print_rt_stats(). The patch is based on above analysis, appears to fix the problem, but is only lightly tested. Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Cheng Xu <chengxu@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/4DCE1F12.6040609@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_rt.c')
-rw-r--r--kernel/sched_rt.c22
1 files changed, 19 insertions, 3 deletions
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index e7cebdc65f82..f8fcf8297c5f 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -183,6 +183,14 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
183 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period); 183 return ktime_to_ns(rt_rq->tg->rt_bandwidth.rt_period);
184} 184}
185 185
186typedef struct task_group *rt_rq_iter_t;
187
188#define for_each_rt_rq(rt_rq, iter, rq) \
189 for (iter = list_entry_rcu(task_groups.next, typeof(*iter), list); \
190 (&iter->list != &task_groups) && \
191 (rt_rq = iter->rt_rq[cpu_of(rq)]); \
192 iter = list_entry_rcu(iter->list.next, typeof(*iter), list))
193
186static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq) 194static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
187{ 195{
188 list_add_rcu(&rt_rq->leaf_rt_rq_list, 196 list_add_rcu(&rt_rq->leaf_rt_rq_list,
@@ -288,6 +296,11 @@ static inline u64 sched_rt_period(struct rt_rq *rt_rq)
288 return ktime_to_ns(def_rt_bandwidth.rt_period); 296 return ktime_to_ns(def_rt_bandwidth.rt_period);
289} 297}
290 298
299typedef struct rt_rq *rt_rq_iter_t;
300
301#define for_each_rt_rq(rt_rq, iter, rq) \
302 for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
303
291static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq) 304static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
292{ 305{
293} 306}
@@ -402,12 +415,13 @@ next:
402static void __disable_runtime(struct rq *rq) 415static void __disable_runtime(struct rq *rq)
403{ 416{
404 struct root_domain *rd = rq->rd; 417 struct root_domain *rd = rq->rd;
418 rt_rq_iter_t iter;
405 struct rt_rq *rt_rq; 419 struct rt_rq *rt_rq;
406 420
407 if (unlikely(!scheduler_running)) 421 if (unlikely(!scheduler_running))
408 return; 422 return;
409 423
410 for_each_leaf_rt_rq(rt_rq, rq) { 424 for_each_rt_rq(rt_rq, iter, rq) {
411 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq); 425 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
412 s64 want; 426 s64 want;
413 int i; 427 int i;
@@ -487,6 +501,7 @@ static void disable_runtime(struct rq *rq)
487 501
488static void __enable_runtime(struct rq *rq) 502static void __enable_runtime(struct rq *rq)
489{ 503{
504 rt_rq_iter_t iter;
490 struct rt_rq *rt_rq; 505 struct rt_rq *rt_rq;
491 506
492 if (unlikely(!scheduler_running)) 507 if (unlikely(!scheduler_running))
@@ -495,7 +510,7 @@ static void __enable_runtime(struct rq *rq)
495 /* 510 /*
496 * Reset each runqueue's bandwidth settings 511 * Reset each runqueue's bandwidth settings
497 */ 512 */
498 for_each_leaf_rt_rq(rt_rq, rq) { 513 for_each_rt_rq(rt_rq, iter, rq) {
499 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq); 514 struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
500 515
501 raw_spin_lock(&rt_b->rt_runtime_lock); 516 raw_spin_lock(&rt_b->rt_runtime_lock);
@@ -1796,10 +1811,11 @@ extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq);
1796 1811
1797static void print_rt_stats(struct seq_file *m, int cpu) 1812static void print_rt_stats(struct seq_file *m, int cpu)
1798{ 1813{
1814 rt_rq_iter_t iter;
1799 struct rt_rq *rt_rq; 1815 struct rt_rq *rt_rq;
1800 1816
1801 rcu_read_lock(); 1817 rcu_read_lock();
1802 for_each_leaf_rt_rq(rt_rq, cpu_rq(cpu)) 1818 for_each_rt_rq(rt_rq, iter, cpu_rq(cpu))
1803 print_rt_rq(m, cpu, rt_rq); 1819 print_rt_rq(m, cpu, rt_rq);
1804 rcu_read_unlock(); 1820 rcu_read_unlock();
1805} 1821}