Messages in this thread | | | Date | Tue, 20 Aug 2013 09:06:50 +0900 | From | Yoshihiro YUNOMAE <> | Subject | Re: Re: [PATCH] [BUGFIX] crash/ioapic: Prevent crash_kexec() from deadlocking of ioapic_lock |
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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@hitachi.com> 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@hitachi.com> >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Ingo Molnar <mingo@redhat.com> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: x86@kernel.org >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Andi Kleen <ak@linux.intel.com> >> Cc: Seiji Aguchi <seiji.aguchi@hds.com> >> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> >> Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc> >> Cc: Joerg Roedel <joro@8bytes.org> >> Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> >> Cc: "Eric W. Biederman" <ebiederm@xmission.com> >> Cc: Gleb Natapov <gleb@redhat.com> >> Cc: Marcelo Tosatti <mtosatti@redhat.com> >> Cc: linux-kernel@vger.kernel.org >> Cc: stable@vger.kernel.org >> --- >> 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
-- Yoshihiro YUNOMAE Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: yoshihiro.yunomae.ez@hitachi.com
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