3.8.13.14 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Yoshihiro YUNOMAE <[email protected]> commit 17405453f4ad0220721a29978692081be6392b8f upstream. Prevent crash_kexec() from deadlocking on ioapic_lock. When crash_kexec() is executed on a CPU, the CPU will take ioapic_lock in disable_IO_APIC(). So if the cpu gets an NMI while locking ioapic_lock, a deadlock will happen. In this patch, ioapic_lock is zapped/initialized before disable_IO_APIC(). You can reproduce this deadlock the following way: 1. Add mdelay(1000) after raw_spin_lock_irqsave() in native_ioapic_set_affinity()@arch/x86/kernel/apic/io_apic.c Although the deadlock can occur without this modification, it will increase the potential of the deadlock problem. 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 on ioapic_lock in crash_kexec()->machine_crash_shutdown()-> native_machine_crash_shutdown()->disable_IO_APIC()->clear_IO_APIC()-> clear_IO_APIC_pin()->ioapic_read_entry(). Signed-off-by: Yoshihiro YUNOMAE <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Gleb Natapov <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: Joerg Roedel <[email protected]> Cc: Marcelo Tosatti <[email protected]> Cc: Hidehiro Kawai <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: Zhang Yanfei <[email protected]> Cc: Eric W. Biederman <[email protected]> Cc: [email protected] Cc: Masami Hiramatsu <[email protected]> Cc: Seiji Aguchi <[email protected]> Link: http://lkml.kernel.org/r/20130820070107.28245.83806.stgit@yunodevel Signed-off-by: Ingo Molnar <[email protected]> [ kamal: 3.8 stable prereq for 522e664 x86/apic: Disable I/O APIC before shutdown of the local APIC ] Signed-off-by: Kamal Mostafa <[email protected]> --- arch/x86/include/asm/apic.h | 2 ++ arch/x86/kernel/apic/io_apic.c | 5 +++++ arch/x86/kernel/crash.c | 4 +++- 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 3388034..cb8bc81 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -688,4 +688,6 @@ extern int default_check_phys_apicid_present(int phys_apicid); #endif /* CONFIG_X86_LOCAL_APIC */ +extern void ioapic_zap_locks(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 b739d39..c605173 100644 --- a/arch/x86/kernel/apic/io_apic.c +++ b/arch/x86/kernel/apic/io_apic.c @@ -1513,6 +1513,11 @@ static void __init setup_timer_IRQ0_pin(unsigned int ioapic_idx, ioapic_write_entry(ioapic_idx, pin, entry); } +void ioapic_zap_locks(void) +{ + raw_spin_lock_init(&ioapic_lock); +} + __apicdebuginit(void) print_IO_APIC(int ioapic_idx) { int i; diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index 74467fe..e0e0841 100644 --- a/arch/x86/kernel/crash.c +++ b/arch/x86/kernel/crash.c @@ -128,7 +128,9 @@ void native_machine_crash_shutdown(struct pt_regs *regs) cpu_emergency_svm_disable(); lapic_shutdown(); -#if defined(CONFIG_X86_IO_APIC) +#ifdef CONFIG_X86_IO_APIC + /* Prevent crash_kexec() from deadlocking on ioapic_lock. */ + ioapic_zap_locks(); disable_IO_APIC(); #endif #ifdef CONFIG_HPET_TIMER -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
