aboutsummaryrefslogtreecommitdiff
path: root/kernel/sched_fair.c
diff options
context:
space:
mode:
authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-04-07 14:09:50 +0200
committerIngo Molnar <mingo@elte.hu>2011-04-11 12:58:19 +0200
commitdce840a08702bd13a9a186e07e63d1ef82256b5e (patch)
tree168bb98aed7f5761ebe31aa92c34959e9d0f238a /kernel/sched_fair.c
parenta9c9a9b6bff27ac9c746344a9c1a19bf3327002c (diff)
downloadlinux-linaro-stable-dce840a08702bd13a9a186e07e63d1ef82256b5e.tar.gz
sched: Dynamically allocate sched_domain/sched_group data-structures
Instead of relying on static allocations for the sched_domain and sched_group trees, dynamically allocate and RCU free them. Allocating this dynamically also allows for some build_sched_groups() simplification since we can now (like with other simplifications) rely on the sched_domain tree instead of hard-coded knowledge. One tricky to note is that detach_destroy_domains() needs to hold rcu_read_lock() over the entire tear-down, per-cpu is not sufficient since that can lead to partial sched_group existance (could possibly be solved by doing the tear-down backwards but this is much more robust). A concequence of the above is that we can no longer print the sched_domain debug stuff from cpu_attach_domain() since that might now run with preemption disabled (due to classic RCU etc.) and sched_domain_debug() does some GFP_KERNEL allocations. Another thing to note is that we now fully rely on normal RCU and not RCU-sched, this is because with the new and exiting RCU flavours we grew over the years BH doesn't necessarily hold off RCU-sched grace periods (-rt is known to break this). This would in fact already cause us grief since we do sched_domain/sched_group iterations from softirq context. This patch is somewhat larger than I would like it to be, but I didn't find any means of shrinking/splitting this. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20110407122942.245307941@chello.nl Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c30
1 files changed, 24 insertions, 6 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 4ee50f0af8d1..4a8ac7c2a18e 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1622,6 +1622,7 @@ static int select_idle_sibling(struct task_struct *p, int target)
/*
* Otherwise, iterate the domains and find an elegible idle cpu.
*/
+ rcu_read_lock();
for_each_domain(target, sd) {
if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
break;
@@ -1641,6 +1642,7 @@ static int select_idle_sibling(struct task_struct *p, int target)
cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
break;
}
+ rcu_read_unlock();
return target;
}
@@ -1673,6 +1675,7 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
new_cpu = prev_cpu;
}
+ rcu_read_lock();
for_each_domain(cpu, tmp) {
if (!(tmp->flags & SD_LOAD_BALANCE))
continue;
@@ -1723,9 +1726,10 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
if (affine_sd) {
if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
- return select_idle_sibling(p, cpu);
- else
- return select_idle_sibling(p, prev_cpu);
+ prev_cpu = cpu;
+
+ new_cpu = select_idle_sibling(p, prev_cpu);
+ goto unlock;
}
while (sd) {
@@ -1766,6 +1770,8 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
}
/* while loop will break here if sd == NULL */
}
+unlock:
+ rcu_read_unlock();
return new_cpu;
}
@@ -3462,6 +3468,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
raw_spin_unlock(&this_rq->lock);
update_shares(this_cpu);
+ rcu_read_lock();
for_each_domain(this_cpu, sd) {
unsigned long interval;
int balance = 1;
@@ -3483,6 +3490,7 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
break;
}
}
+ rcu_read_unlock();
raw_spin_lock(&this_rq->lock);
@@ -3531,6 +3539,7 @@ static int active_load_balance_cpu_stop(void *data)
double_lock_balance(busiest_rq, target_rq);
/* Search for an sd spanning us and the target CPU. */
+ rcu_read_lock();
for_each_domain(target_cpu, sd) {
if ((sd->flags & SD_LOAD_BALANCE) &&
cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
@@ -3546,6 +3555,7 @@ static int active_load_balance_cpu_stop(void *data)
else
schedstat_inc(sd, alb_failed);
}
+ rcu_read_unlock();
double_unlock_balance(busiest_rq, target_rq);
out_unlock:
busiest_rq->active_balance = 0;
@@ -3672,6 +3682,7 @@ static int find_new_ilb(int cpu)
{
struct sched_domain *sd;
struct sched_group *ilb_group;
+ int ilb = nr_cpu_ids;
/*
* Have idle load balancer selection from semi-idle packages only
@@ -3687,20 +3698,25 @@ static int find_new_ilb(int cpu)
if (cpumask_weight(nohz.idle_cpus_mask) < 2)
goto out_done;
+ rcu_read_lock();
for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
ilb_group = sd->groups;
do {
- if (is_semi_idle_group(ilb_group))
- return cpumask_first(nohz.grp_idle_mask);
+ if (is_semi_idle_group(ilb_group)) {
+ ilb = cpumask_first(nohz.grp_idle_mask);
+ goto unlock;
+ }
ilb_group = ilb_group->next;
} while (ilb_group != sd->groups);
}
+unlock:
+ rcu_read_unlock();
out_done:
- return nr_cpu_ids;
+ return ilb;
}
#else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
@@ -3845,6 +3861,7 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle)
update_shares(cpu);
+ rcu_read_lock();
for_each_domain(cpu, sd) {
if (!(sd->flags & SD_LOAD_BALANCE))
continue;
@@ -3890,6 +3907,7 @@ out:
if (!balance)
break;
}
+ rcu_read_unlock();
/*
* next_balance will be updated only when there is a need.