From fd8a7de177b6f56a0fc59ad211c197a7df06b1ad Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 20 Jul 2010 14:34:50 +0200
Subject: [PATCH 1/3] x86: cpu-hotplug: Prevent softirq wakeup on wrong CPU
After a newly plugged CPU sets the cpu_online bit it enables
interrupts and goes idle. The cpu which brought up the new cpu waits
for the cpu_online bit and when it observes it, it sets the cpu_active
bit for this cpu. The cpu_active bit is the relevant one for the
scheduler to consider the cpu as a viable target.
With forced threaded interrupt handlers which imply forced threaded
softirqs we observed the following race:
cpu 0 cpu 1
bringup(cpu1);
set_cpu_online(smp_processor_id(), true);
local_irq_enable();
while (!cpu_online(cpu1));
timer_interrupt()
-> wake_up(softirq_thread_cpu1);
-> enqueue_on(softirq_thread_cpu1, cpu0);
^^^^
cpu_notify(CPU_ONLINE, cpu1);
-> sched_cpu_active(cpu1)
-> set_cpu_active((cpu1, true);
When an interrupt happens before the cpu_active bit is set by the cpu
which brought up the newly onlined cpu, then the scheduler refuses to
enqueue the woken thread which is bound to that newly onlined cpu on
that newly onlined cpu due to the not yet set cpu_active bit and
selects a fallback runqueue. Not really an expected and desirable
behaviour.
So far this has only been observed with forced hard/softirq threading,
but in theory this could happen without forced threaded hard/softirqs
as well. It's probably unobservable as it would take a massive
interrupt storm on the newly onlined cpu which causes the softirq loop
to wake up the softirq thread and an even longer delay of the cpu
which waits for the cpu_online bit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@kernel.org # 2.6.39
---
arch/x86/kernel/smpboot.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 33a0c11797de..9fd3137230d4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -285,6 +285,19 @@ notrace static void __cpuinit start_secondary(void *unused)
per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
x86_platform.nmi_init();
+ /*
+ * Wait until the cpu which brought this one up marked it
+ * online before enabling interrupts. If we don't do that then
+ * we can end up waking up the softirq thread before this cpu
+ * reached the active state, which makes the scheduler unhappy
+ * and schedule the softirq thread on the wrong cpu. This is
+ * only observable with forced threaded interrupts, but in
+ * theory it could also happen w/o them. It's just way harder
+ * to achieve.
+ */
+ while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
+ cpu_relax();
+
/* enable local interrupts */
local_irq_enable();
From 977cb76d52e7aa040e18a84b29fe6fd80d79319b Mon Sep 17 00:00:00 2001
From: Florian Fainelli <ffainelli@freebox.fr>
Date: Mon, 6 Jun 2011 10:15:49 +0200
Subject: [PATCH 2/3] x86: devicetree: Add missing
early_init_dt_setup_initrd_arch stub
This patch fixes the following build failure:
drivers/built-in.o: In function `early_init_dt_check_for_initrd':
/home/florian/dev/kernel/x86/linux-2.6-x86/drivers/of/fdt.c:571:
undefined reference to `early_init_dt_setup_initrd_arch'
make: *** [.tmp_vmlinux1] Error 1
which happens as soon as we enable initrd support on a x86 devicetree
platform such as Intel CE4100.
Signed-off-by: Florian Fainelli <ffainelli@freebox.fr>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Maxime Bizon <mbizon@freebox.fr>
Acked-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: stable@kernel.org # 2.6.39
Link: http://lkml.kernel.org/r/201106061015.50039.ffainelli@freebox.fr
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/devicetree.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index 690bc8461835..9aeb78a23de4 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -13,6 +13,7 @@
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/of_pci.h>
+#include <linux/initrd.h>
#include <asm/hpet.h>
#include <asm/irq_controller.h>
@@ -98,6 +99,16 @@ void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
return __alloc_bootmem(size, align, __pa(MAX_DMA_ADDRESS));
}
+#ifdef CONFIG_BLK_DEV_INITRD
+void __init early_init_dt_setup_initrd_arch(unsigned long start,
+ unsigned long end)
+{
+ initrd_start = (unsigned long)__va(start);
+ initrd_end = (unsigned long)__va(end);
+ initrd_below_start_ok = 1;
+}
+#endif
+
void __init add_dtb(u64 data)
{
initial_dtb = data + offsetof(struct setup_data, data);
From 13863a66c9c8a663665445cf05d68de96ff31830 Mon Sep 17 00:00:00 2001
From: Jesper Juhl <jj@chaosbits.net>
Date: Thu, 9 Jun 2011 23:14:58 +0200
Subject: [PATCH 3/3] genirq: Prevent potential NULL dereference in
irq_set_irq_wake()
In kernel/irq/manage.c::irq_set_irq_wake() we call
irq_get_desc_buslock() which may return NULL, but the code
dereferences the result unconditionally.
irq_set_irq_wake() has lots of callers - I checked a few and I couldn't
find anything that guarantees that they won't call it with some input that
will cause irq_get_desc_buslock() to return NULL, so I think it's a good
thing to test and -EINVAL was the most sane error code in this situation
that I could think of.
Not all callers test the return value of irq_set_irq_wake(), but those
that do take != 0 to mean error as far as I can see, so they should be
fine. I guess those that don't test actually should, but that's a
different issue.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Link: http://lkml.kernel.org/r/alpine.LNX.2.00.1106092300360.17868@swampdragon.chaosbits.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/irq/manage.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index d64bafb1afd0..0a7840aeb0fb 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -491,6 +491,9 @@ int irq_set_irq_wake(unsigned int irq, unsigned int on)
struct irq_desc *desc = irq_get_desc_buslock(irq, &flags);
int ret = 0;
+ if (!desc)
+ return -EINVAL;
+
/* wakeup-capable irqs can be shared between drivers that
* don't need to have the same sleep mode behaviors.
*/