[git pull] scheduler/misc fixes

Ingo Molnar
2008-04-24T22:55:54Z

Linus, please pull the latest scheduler/misc fixes git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-fixes.git for-linus

a scheduler fix, a (long-standing) seqlock fix and a softlockup+nohz
fix.

Thanks,

Ingo

------------------>
Ingo Molnar (2):
seqlock: livelock fix
softlockup: fix NOHZ wakeup

Peter Zijlstra (1):
sched: fix share (re)distribution

include/linux/seqlock.h | 46 ++++++++++++++++++++++++++++----------------
kernel/sched.c | 47 +--------------------------------------------
kernel/time/tick-sched.c | 1 +
3 files changed, 32 insertions(+), 62 deletions(-)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 26e4925..632205c 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -85,23 +85,29 @@ static inline int write_tryseqlock(seqlock_t *sl)
/* Start of read calculation -- fetch last complete writer token */
static __always_inline unsigned read_seqbegin(const seqlock_t *sl)
{
- unsigned ret = sl->sequence;
+ unsigned ret;
+
+repeat:
+ ret = sl->sequence;
smp_rmb();
+ if (unlikely(ret & 1)) {
+ cpu_relax();
+ goto repeat;
+ }
+
return ret;
}

-/* Test if reader processed invalid data.
- * If initial values is odd,
- * then writer had already started when section was entered
- * If sequence value changed
- * then writer changed data while in section
- *
- * Using xor saves one conditional branch.
+/*
+ * Test if reader processed invalid data.
+ *
+ * If sequence value changed then writer changed data while in section.
*/
-static __always_inline int read_seqretry(const seqlock_t *sl, unsigned iv)
+static __always_inline int read_seqretry(const seqlock_t *sl, unsigned start)
{
smp_rmb();
- return (iv & 1) | (sl->sequence ^ iv);
+
+ return (sl->sequence != start);
}

@@ -122,20 +128,26 @@ typedef struct seqcount {
/* Start of read using pointer to a sequence counter only. */
static inline unsigned read_seqcount_begin(const seqcount_t *s)
{
- unsigned ret = s->sequence;
+ unsigned ret;
+
+repeat:
+ ret = s->sequence;
smp_rmb();
+ if (unlikely(ret & 1)) {
+ cpu_relax();
+ goto repeat;
+ }
return ret;
}

-/* Test if reader processed invalid data.
- * Equivalent to: iv is odd or sequence number has changed.
- * (iv & 1) || (*s != iv)
- * Using xor saves one conditional branch.
+/*
+ * Test if reader processed invalid data because sequence number has changed.
*/
-static inline int read_seqcount_retry(const seqcount_t *s, unsigned iv)
+static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
{
smp_rmb();
- return (iv & 1) | (s->sequence ^ iv);
+
+ return s->sequence != start;
}

diff --git a/kernel/sched.c b/kernel/sched.c
index 0014b03..85e1721 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1657,42 +1657,6 @@ void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
}

/*
- * Redistribute tg->shares amongst all tg->cfs_rq[]s.
- */
-static void __aggregate_redistribute_shares(struct task_group *tg)
-{
- int i, max_cpu = smp_processor_id();
- unsigned long rq_weight = 0;
- unsigned long shares, max_shares = 0, shares_rem = tg->shares;
-
- for_each_possible_cpu(i)
- rq_weight += tg->cfs_rq[i]->load.weight;
-
- for_each_possible_cpu(i) {
- /*
- * divide shares proportional to the rq_weights.
- */
- shares = tg->shares * tg->cfs_rq[i]->load.weight;
- shares /= rq_weight + 1;
-
- tg->cfs_rq[i]->shares = shares;
-
- if (shares > max_shares) {
- max_shares = shares;
- max_cpu = i;
- }
- shares_rem -= shares;
- }
-
- /*
- * Ensure it all adds up to tg->shares; we can loose a few
- * due to rounding down when computing the per-cpu shares.
- */
- if (shares_rem)
- tg->cfs_rq[max_cpu]->shares += shares_rem;
-}
-
-/*
* Compute the weight of this group on the given cpus.
*/
static
@@ -1701,18 +1665,11 @@ void aggregate_group_shares(struct task_group *tg, struct sched_domain *sd)
unsigned long shares = 0;
int i;

-again:
for_each_cpu_mask(i, sd->span)
shares += tg->cfs_rq[i]->shares;

- /*
- * When the span doesn't have any shares assigned, but does have
- * tasks to run do a machine wide rebalance (should be rare).
- */
- if (unlikely(!shares && aggregate(tg, sd)->rq_weight)) {
- __aggregate_redistribute_shares(tg);
- goto again;
- }
+ if ((!shares && aggregate(tg, sd)->rq_weight) || shares > tg->shares)
+ shares = tg->shares;

aggregate(tg, sd)->shares = shares;
}
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index d358d4e..b854a89 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -393,6 +393,7 @@ void tick_nohz_restart_sched_tick(void)
sub_preempt_count(HARDIRQ_OFFSET);
}

+ touch_softlockup_watchdog();
/*
* Cancel the scheduled timer and restore the tick
*/