linux.kernel - 26 new messages in 10 topics - digest

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Today's topics:

* sched: Fix race on toggling cfs_bandwidth_used - 9 messages, 1 author
http://groups.google.com/group/linux.kernel/t/ef25c501937e80d8?hl=en
* packet: fix send path when running with proto == 0 - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/a53824587b1cf92d?hl=en
* x86, e820 disable ACPI Memory Hotplug if memory mapping is specified by user
[v2] - 4 messages, 3 authors
http://groups.google.com/group/linux.kernel/t/4888d1ac18187fba?hl=en
* efi: Dump the EFI page table - 2 messages, 1 author
http://groups.google.com/group/linux.kernel/t/32f26a85f5600001?hl=en
* find missing bug fixes in a stable kernel - 2 messages, 1 author
http://groups.google.com/group/linux.kernel/t/023953357d1f282b?hl=en
* perf probe: Build error with missing libraries - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/ed626ce36201b7f7?hl=en
* x86, acpi memory hotplug, add parameter to disable memory hotplug - 2
messages, 2 authors
http://groups.google.com/group/linux.kernel/t/fea2893681599c3e?hl=en
* mm/memcg: fix endless iteration in reclaim - 3 messages, 1 author
http://groups.google.com/group/linux.kernel/t/da1204ed98ee639c?hl=en
* oprofile: check whether oprofile perf enabled in op_overflow_handler() - 1
messages, 1 author
http://groups.google.com/group/linux.kernel/t/b2cfc5572069b825?hl=en
* ion: Fix sparse non static symbol warnings - 1 messages, 1 author
http://groups.google.com/group/linux.kernel/t/a5c93666f4465611?hl=en

==============================================================================
TOPIC: sched: Fix race on toggling cfs_bandwidth_used
http://groups.google.com/group/linux.kernel/t/ef25c501937e80d8?hl=en
==============================================================================

== 1 of 9 ==
Date: Mon, Jan 13 2014 5:20 pm
From: Greg Kroah-Hartman


3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Ben Segall <bsegall@google.com>

commit 1ee14e6c8cddeeb8a490d7b54cd9016e4bb900b4 upstream.

When we transition cfs_bandwidth_used to false, any currently
throttled groups will incorrectly return false from cfs_rq_throttled.
While tg_set_cfs_bandwidth will unthrottle them eventually, currently
running code (including at least dequeue_task_fair and
distribute_cfs_runtime) will cause errors.

Fix this by turning off cfs_bandwidth_used only after unthrottling all
cfs_rqs.

Tested: toggle bandwidth back and forth on a loaded cgroup. Caused
crashes in minutes without the patch, hasn't crashed with it.

Signed-off-by: Ben Segall <bsegall@google.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: pjt@google.com
Link: http://lkml.kernel.org/r/20131016181611.22647.80365.stgit@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/sched/core.c | 9 ++++++++-
kernel/sched/fair.c | 16 +++++++++-------
kernel/sched/sched.h | 3 ++-
3 files changed, 19 insertions(+), 9 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7906,7 +7906,12 @@ static int tg_set_cfs_bandwidth(struct t

runtime_enabled = quota != RUNTIME_INF;
runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
- account_cfs_bandwidth_used(runtime_enabled, runtime_was_enabled);
+ /*
+ * If we need to toggle cfs_bandwidth_used, off->on must occur
+ * before making related changes, and on->off must occur afterwards
+ */
+ if (runtime_enabled && !runtime_was_enabled)
+ cfs_bandwidth_usage_inc();
raw_spin_lock_irq(&cfs_b->lock);
cfs_b->period = ns_to_ktime(period);
cfs_b->quota = quota;
@@ -7932,6 +7937,8 @@ static int tg_set_cfs_bandwidth(struct t
unthrottle_cfs_rq(cfs_rq);
raw_spin_unlock_irq(&rq->lock);
}
+ if (runtime_was_enabled && !runtime_enabled)
+ cfs_bandwidth_usage_dec();
out_unlock:
mutex_unlock(&cfs_constraints_mutex);

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1393,13 +1393,14 @@ static inline bool cfs_bandwidth_used(vo
return static_key_false(&__cfs_bandwidth_used);
}

-void account_cfs_bandwidth_used(int enabled, int was_enabled)
+void cfs_bandwidth_usage_inc(void)
{
- /* only need to count groups transitioning between enabled/!enabled */
- if (enabled && !was_enabled)
- static_key_slow_inc(&__cfs_bandwidth_used);
- else if (!enabled && was_enabled)
- static_key_slow_dec(&__cfs_bandwidth_used);
+ static_key_slow_inc(&__cfs_bandwidth_used);
+}
+
+void cfs_bandwidth_usage_dec(void)
+{
+ static_key_slow_dec(&__cfs_bandwidth_used);
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
@@ -1407,7 +1408,8 @@ static bool cfs_bandwidth_used(void)
return true;
}

-void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
+void cfs_bandwidth_usage_inc(void) {}
+void cfs_bandwidth_usage_dec(void) {}