1 files changed, 120 insertions, 0 deletions

diff --git a/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.25/0047-workqueue-perform-cpu-down-operations-from-low-prior.patch b/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.25/0047-workqueue-perform-cpu-down-operations-from-low-prior.patch
new file mode 100644
index 00000000..772eafb5
--- /dev/null
+++ b/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.25/0047-workqueue-perform-cpu-down-operations-from-low-prior.patch
@@ -0,0 +1,120 @@
+From 47ba7731c120a3ed09336d18b85493bd85d926f2 Mon Sep 17 00:00:00 2001
+From: Tejun Heo <tj@kernel.org>
+Date: Tue, 17 Jul 2012 12:39:26 -0700
+Subject: [PATCH 47/73] workqueue: perform cpu down operations from low
+ priority cpu_notifier()
+
+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: Ben Hutchings <ben@decadent.org.uk>
+---
+ include/linux/cpu.h |    5 +++--
+ kernel/workqueue.c  |   38 +++++++++++++++++++++++++++++++++++++-
+ 2 files changed, 40 insertions(+), 3 deletions(-)
+
+diff --git a/include/linux/cpu.h b/include/linux/cpu.h
+index 6cb60fd..c692acc 100644
+--- 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,
+ };
+ 
+ #define CPU_ONLINE             0x0002 /* CPU (unsigned)v is up */
+diff --git a/kernel/workqueue.c b/kernel/workqueue.c
+index 7947e16..a650bee 100644
+--- a/kernel/workqueue.c
++++ b/kernel/workqueue.c
+@@ -3586,6 +3586,41 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
+        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 {
+@@ -3779,7 +3814,8 @@ 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) {
+-- 
+1.7.7.6
+