Hi Ingo,
Thank you for fixing typos!
OK, I'll fix them and rename to ioapic_zap_locks().
Thank you again!
Yoshihiro YUNOMAE
(2013/08/19 18:46), Ingo Molnar wrote:
* Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx> wrote:
Prevent crash_kexec() from deadlocking of ioapic_lock.
s/of/on
When crash_kexec() is executed on a cpu, the cpu will get
ioapic_lock in disable_IO_APIC(). So if the cpu gets NMI
while locking ioapic_lock, a deadlock wiil happen. In
s/will
this patch, ioapic_lock is initialized before
disable_IO_APIC().
To confirm this deadlocking, you'll set up as follows:
s/deadlocking/deadlock
1. Add mdelay(1000) after raw_spin_lock_irqsave() in
native_ioapic_set_affinity()@arch/x86/kernel/apic/io_apic.c
Although the deadlocking can occur without this modification, it will
increase the potential of the deadlocking problem.
s/deadlocking/deadlock
2. Build and install the kernel
3. Set up the OS which will run panic() and kexec when NMI is injected
# echo "kernel.unknown_nmi_panic=1" >> /etc/sysctl.conf
# vim /etc/default/grub
add "nmi_watchdog=0 crashkernel=256M" in GRUB_CMDLINE_LINUX line
# grub2-mkconfig
4. Reboot the OS
5. Run following command for each vcpu on the guest
# while true; do echo <CPU num> > /proc/irq/<IO-APIC-edge or IO-APIC-fasteoi>/smp_affinitity; done;
By running this command, cpus will get ioapic_lock for setting affinity.
6. Inject NMI (push a dump button or execute 'virsh inject-nmi <domain>' if you
use VM)
After injecting NMI, panic() is called in an nmi-handler context.
Then, kexec will normally run in panic(), but the operation will be stopped
by deadlock of ioapic_lock in crash_kexec()->machine_crash_shutdown()->
s/of/on
native_machine_crash_shutdown()->disable_IO_APIC()->clear_IO_APIC()->
clear_IO_APIC_pin()->ioapic_read_entry().
I suppose we could do this patch if it's a common
occurance.
A few minor details need fixing:
Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Seiji Aguchi <seiji.aguchi@xxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <sebastian@xxxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: Zhang Yanfei <zhangyanfei@xxxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
---
arch/x86/include/asm/apic.h | 2 ++
arch/x86/kernel/apic/io_apic.c | 5 +++++
arch/x86/kernel/crash.c | 4 ++++
3 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index f8119b5..ddb06af 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -715,4 +715,6 @@ static inline void exiting_ack_irq(void)
ack_APIC_irq();
}
+extern void ioapic_lock_init(void);
+
#endif /* _ASM_X86_APIC_H */
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 9ed796c..2816c07 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1534,6 +1534,11 @@ void intel_ir_io_apic_print_entries(unsigned int apic,
}
}
+void ioapic_lock_init(void)
+{
+ raw_spin_lock_init(&ioapic_lock);
+}
Please name this ioapic_zap_locks() to make clear that this
is crash handling related.
+
__apicdebuginit(void) print_IO_APIC(int ioapic_idx)
{
union IO_APIC_reg_00 reg_00;
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 74467fe..ea039d5 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -129,6 +129,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
lapic_shutdown();
#if defined(CONFIG_X86_IO_APIC)
Please enhance this #ifdef while at it.
+ /*
+ * Prevent crash_kexec() from deadlocking of ioapic_lock.
+ */
s/of/on.
Also, single-line comment can go /* here */.
+ ioapic_lock_init();
disable_IO_APIC();
#endif
#ifdef CONFIG_HPET_TIMER
Thanks,
Ingo
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--
Yoshihiro YUNOMAE
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: yoshihiro.yunomae.ez@xxxxxxxxxxx
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