Add patch to fix cpu pinning after suspend/resume (rhbz 714271)
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Josh Boyer
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139
CPU-hotplug-cpusets-suspend-Dont-modify-cpusets-during.patch
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139
CPU-hotplug-cpusets-suspend-Dont-modify-cpusets-during.patch
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From 0c1508129adc051fabaf8debefea79baa2f1a81b Mon Sep 17 00:00:00 2001
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From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
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Date: Thu, 24 May 2012 19:46:26 +0530
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Subject: [PATCH] CPU hotplug, cpusets, suspend: Don't modify cpusets during
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suspend/resume
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In the event of CPU hotplug, the kernel modifies the cpusets' cpus_allowed
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masks as and when necessary to ensure that the tasks belonging to the cpusets
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have some place (online CPUs) to run on. And regular CPU hotplug is
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destructive in the sense that the kernel doesn't remember the original cpuset
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configurations set by the user, across hotplug operations.
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However, suspend/resume (which uses CPU hotplug) is a special case in which
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the kernel has the responsibility to restore the system (during resume), to
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exactly the same state it was in before suspend.
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In order to achieve that, do the following:
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1. Don't modify cpusets during suspend/resume. At all.
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In particular, don't move the tasks from one cpuset to another, and
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don't modify any cpuset's cpus_allowed mask. So, simply ignore cpusets
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during the CPU hotplug operations that are carried out in the
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suspend/resume path.
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2. However, cpusets and sched domains are related. We just want to avoid
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altering cpusets alone. So, to keep the sched domains updated, build
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a single sched domain (containing all active cpus) during each of the
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CPU hotplug operations carried out in s/r path, effectively ignoring
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the cpusets' cpus_allowed masks.
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(Since userspace is frozen while doing all this, it will go unnoticed.)
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3. During the last CPU online operation during resume, build the sched
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domains by looking up the (unaltered) cpusets' cpus_allowed masks.
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That will bring back the system to the same original state as it was in
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before suspend.
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Ultimately, this will not only solve the cpuset problem related to suspend
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resume (ie., restores the cpusets to exactly what it was before suspend, by
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not touching it at all) but also speeds up suspend/resume because we avoid
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running cpuset update code for every CPU being offlined/onlined.
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Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Andrew Morton <akpm@linux-foundation.org>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Link: http://lkml.kernel.org/r/20120524141611.3692.20155.stgit@srivatsabhat.in.ibm.com
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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---
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kernel/cpuset.c | 3 +++
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kernel/sched/core.c | 40 ++++++++++++++++++++++++++++++++++++----
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2 files changed, 39 insertions(+), 4 deletions(-)
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--- linux-3.4.6-3.1.fc17.noarch.orig/kernel/cpuset.c
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+++ linux-3.4.6-3.1.fc17.noarch/kernel/cpuset.c
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@@ -2065,6 +2065,9 @@ static void scan_for_empty_cpusets(struc
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* (of no affect) on systems that are actively using CPU hotplug
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* but making no active use of cpusets.
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*
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+ * The only exception to this is suspend/resume, where we don't
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+ * modify cpusets at all.
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+ *
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* This routine ensures that top_cpuset.cpus_allowed tracks
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* cpu_active_mask on each CPU hotplug (cpuhp) event.
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*
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--- linux-3.4.6-3.1.fc17.noarch.orig/kernel/sched/core.c
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+++ linux-3.4.6-3.1.fc17.noarch/kernel/sched/core.c
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@@ -6931,34 +6931,66 @@ int __init sched_create_sysfs_power_savi
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}
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#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
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+static int num_cpus_frozen; /* used to mark begin/end of suspend/resume */
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+
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/*
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* Update cpusets according to cpu_active mask. If cpusets are
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* disabled, cpuset_update_active_cpus() becomes a simple wrapper
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* around partition_sched_domains().
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+ *
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+ * If we come here as part of a suspend/resume, don't touch cpusets because we
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+ * want to restore it back to its original state upon resume anyway.
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*/
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static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
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void *hcpu)
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{
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- switch (action & ~CPU_TASKS_FROZEN) {
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+ switch (action) {
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+ case CPU_ONLINE_FROZEN:
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+ case CPU_DOWN_FAILED_FROZEN:
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+
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+ /*
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+ * num_cpus_frozen tracks how many CPUs are involved in suspend
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+ * resume sequence. As long as this is not the last online
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+ * operation in the resume sequence, just build a single sched
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+ * domain, ignoring cpusets.
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+ */
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+ num_cpus_frozen--;
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+ if (likely(num_cpus_frozen)) {
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+ partition_sched_domains(1, NULL, NULL);
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+ break;
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+ }
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+
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+ /*
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+ * This is the last CPU online operation. So fall through and
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+ * restore the original sched domains by considering the
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+ * cpuset configurations.
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+ */
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+
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case CPU_ONLINE:
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case CPU_DOWN_FAILED:
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cpuset_update_active_cpus();
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- return NOTIFY_OK;
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+ break;
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default:
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return NOTIFY_DONE;
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}
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+ return NOTIFY_OK;
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}
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static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
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void *hcpu)
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{
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- switch (action & ~CPU_TASKS_FROZEN) {
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+ switch (action) {
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case CPU_DOWN_PREPARE:
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cpuset_update_active_cpus();
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- return NOTIFY_OK;
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+ break;
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+ case CPU_DOWN_PREPARE_FROZEN:
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+ num_cpus_frozen++;
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+ partition_sched_domains(1, NULL, NULL);
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+ break;
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default:
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return NOTIFY_DONE;
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}
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+ return NOTIFY_OK;
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}
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void __init sched_init_smp(void)
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11
kernel.spec
11
kernel.spec
@ -54,7 +54,7 @@ Summary: The Linux kernel
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# For non-released -rc kernels, this will be appended after the rcX and
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# gitX tags, so a 3 here would become part of release "0.rcX.gitX.3"
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#
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%global baserelease 1
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%global baserelease 2
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%global fedora_build %{baserelease}
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# base_sublevel is the kernel version we're starting with and patching
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@ -761,6 +761,9 @@ Patch22056: crypto-aesni-intel-fix-wrong-kfree-pointer.patch
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#rhbz 772730
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Patch22058: ACPI-AC-check-the-return-value-of-power_supply_register.patch
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#rhbz 714271
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Patch22060: CPU-hotplug-cpusets-suspend-Dont-modify-cpusets-during.patch
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# END OF PATCH DEFINITIONS
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%endif
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@ -1409,6 +1412,9 @@ ApplyPatch crypto-aesni-intel-fix-wrong-kfree-pointer.patch
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#rhbz 772730
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ApplyPatch ACPI-AC-check-the-return-value-of-power_supply_register.patch
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#rhbz 714271
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ApplyPatch CPU-hotplug-cpusets-suspend-Dont-modify-cpusets-during.patch
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# END OF PATCH APPLICATIONS
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%endif
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@ -2147,6 +2153,9 @@ fi
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# and build.
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%changelog
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* Wed Jul 25 2012 Josh Boyer <jwboyer@redhat.com>
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- Add patch to fix cpu pinning after suspend/resume (rhbz 714271)
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* Thu Jul 19 2012 Josh Boyer <jwboyer@redhat.com> - 3.4.6-1
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- Linux v3.4.6
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