3.0-stable patches

added patches:
	workqueue-perform-cpu-down-operations-from-low-priority-cpu_notifier.patch

diff --git a/queue-3.0/series b/queue-3.0/series
index 4e4af55106362f590561e0f401607e333af2f4ed..4b646a3b4583158cc7947068fef2aab0c7754695 100644 (file)
--- a/queue-3.0/series
+++ b/queue-3.0/series
@@ -14,3 +14,4 @@ usb-gadget-fix-g_ether-interface-link-status.patch
 locks-fix-checking-of-fcntl_setlease-argument.patch
 ftrace-disable-function-tracing-during-suspend-resume-and-hibernation-again.patch
 stable-update-references-to-older-2.6-versions-for-3.x.patch
+workqueue-perform-cpu-down-operations-from-low-priority-cpu_notifier.patch

diff --git a/queue-3.0/workqueue-perform-cpu-down-operations-from-low-priority-cpu_notifier.patch b/queue-3.0/workqueue-perform-cpu-down-operations-from-low-priority-cpu_notifier.patch
new file mode 100644 (file)
index 0000000..985a349
--- /dev/null
+++ b/queue-3.0/workqueue-perform-cpu-down-operations-from-low-priority-cpu_notifier.patch
@@ -0,0 +1,115 @@
+From 6575820221f7a4dd6eadecf7bf83cdd154335eda Mon Sep 17 00:00:00 2001
+From: Tejun Heo <tj@kernel.org>
+Date: Tue, 17 Jul 2012 12:39:26 -0700
+Subject: workqueue: perform cpu down operations from low priority cpu_notifier()
+
+From: Tejun Heo <tj@kernel.org>
+
+commit 6575820221f7a4dd6eadecf7bf83cdd154335eda upstream.
+
+Currently, all workqueue cpu hotplug operations run off
+CPU_PRI_WORKQUEUE which is higher than normal notifiers.  This is to
+ensure that workqueue is up and running while bringing up a CPU before
+other notifiers try to use workqueue on the CPU.
+
+Per-cpu workqueues are supposed to remain working and bound to the CPU
+for normal CPU_DOWN_PREPARE notifiers.  This holds mostly true even
+with workqueue offlining running with higher priority because
+workqueue CPU_DOWN_PREPARE only creates a bound trustee thread which
+runs the per-cpu workqueue without concurrency management without
+explicitly detaching the existing workers.
+
+However, if the trustee needs to create new workers, it creates
+unbound workers which may wander off to other CPUs while
+CPU_DOWN_PREPARE notifiers are in progress.  Furthermore, if the CPU
+down is cancelled, the per-CPU workqueue may end up with workers which
+aren't bound to the CPU.
+
+While reliably reproducible with a convoluted artificial test-case
+involving scheduling and flushing CPU burning work items from CPU down
+notifiers, this isn't very likely to happen in the wild, and, even
+when it happens, the effects are likely to be hidden by the following
+successful CPU down.
+
+Fix it by using different priorities for up and down notifiers - high
+priority for up operations and low priority for down operations.
+
+Workqueue cpu hotplug operations will soon go through further cleanup.
+
+Signed-off-by: Tejun Heo <tj@kernel.org>
+Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ include/linux/cpu.h |    5 +++--
+ kernel/workqueue.c  |   38 +++++++++++++++++++++++++++++++++++++-
+ 2 files changed, 40 insertions(+), 3 deletions(-)
+
+--- a/include/linux/cpu.h
++++ b/include/linux/cpu.h
+@@ -66,8 +66,9 @@ enum {
+       /* migration should happen before other stuff but after perf */
+       CPU_PRI_PERF            = 20,
+       CPU_PRI_MIGRATION       = 10,
+-      /* prepare workqueues for other notifiers */
+-      CPU_PRI_WORKQUEUE       = 5,
++      /* bring up workqueues before normal notifiers and down after */
++      CPU_PRI_WORKQUEUE_UP    = 5,
++      CPU_PRI_WORKQUEUE_DOWN  = -5,
+ };
+ 
+ #ifdef CONFIG_SMP
+--- a/kernel/workqueue.c
++++ b/kernel/workqueue.c
+@@ -3561,6 +3561,41 @@ static int __devinit workqueue_cpu_callb
+       return notifier_from_errno(0);
+ }
+ 
++/*
++ * Workqueues should be brought up before normal priority CPU notifiers.
++ * This will be registered high priority CPU notifier.
++ */
++static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb,
++                                             unsigned long action,
++                                             void *hcpu)
++{
++      switch (action & ~CPU_TASKS_FROZEN) {
++      case CPU_UP_PREPARE:
++      case CPU_UP_CANCELED:
++      case CPU_DOWN_FAILED:
++      case CPU_ONLINE:
++              return workqueue_cpu_callback(nfb, action, hcpu);
++      }
++      return NOTIFY_OK;
++}
++
++/*
++ * Workqueues should be brought down after normal priority CPU notifiers.
++ * This will be registered as low priority CPU notifier.
++ */
++static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb,
++                                               unsigned long action,
++                                               void *hcpu)
++{
++      switch (action & ~CPU_TASKS_FROZEN) {
++      case CPU_DOWN_PREPARE:
++      case CPU_DYING:
++      case CPU_POST_DEAD:
++              return workqueue_cpu_callback(nfb, action, hcpu);
++      }
++      return NOTIFY_OK;
++}
++
+ #ifdef CONFIG_SMP
+ 
+ struct work_for_cpu {
+@@ -3754,7 +3789,8 @@ static int __init init_workqueues(void)
+       unsigned int cpu;
+       int i;
+ 
+-      cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE);
++      cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP);
++      cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN);
+ 
+       /* initialize gcwqs */
+       for_each_gcwq_cpu(cpu) {