Messages in this thread Patch in this message | | | Date | Fri, 29 Mar 2013 15:22:38 +0800 | From | Zhenzhong Duan <> | Subject | [PATCH] xen: Don't call arch_trigger_all_cpu_backtrace in dom0(pvm) |
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nmi isn't supported in dom0, fallback to general all cpu backtrace code.
Without fix, on xapic system, sysrq+l, no backtrace is showed. On x2apic enabled system, got NULL pointer dereference as below.
SysRq : Show backtrace of all active CPUs BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff8125e3cb>] memcpy+0xb/0x120 Call Trace: [<ffffffff81039633>] ? __x2apic_send_IPI_mask+0x73/0x160 [<ffffffff8103973e>] x2apic_send_IPI_all+0x1e/0x20 [<ffffffff8103498c>] arch_trigger_all_cpu_backtrace+0x6c/0xb0 [<ffffffff81501be4>] ? _raw_spin_lock_irqsave+0x34/0x50 [<ffffffff8131654e>] sysrq_handle_showallcpus+0xe/0x10 [<ffffffff8131616d>] __handle_sysrq+0x7d/0x140 [<ffffffff81316230>] ? __handle_sysrq+0x140/0x140 [<ffffffff81316287>] write_sysrq_trigger+0x57/0x60 [<ffffffff811ca996>] proc_reg_write+0x86/0xc0 [<ffffffff8116dd8e>] vfs_write+0xce/0x190 [<ffffffff8116e3e5>] sys_write+0x55/0x90 [<ffffffff8150a242>] system_call_fastpath+0x16/0x1b
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com> Tested-by: Tamon Shiose <tamon.shiose@oracle.com> --- include/linux/nmi.h | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/include/linux/nmi.h b/include/linux/nmi.h index db50840..b845757 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -32,6 +32,8 @@ static inline void touch_nmi_watchdog(void) #ifdef arch_trigger_all_cpu_backtrace static inline bool trigger_all_cpu_backtrace(void) { + if (xen_domain()) + return false; arch_trigger_all_cpu_backtrace(); return true; -- 1.7.3
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