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authorHidehiro Kawai <hidehiro.kawai.ez@hitachi.com>2015-12-14 13:19:13 +0300
committerThomas Gleixner <tglx@linutronix.de>2015-12-19 13:07:01 +0300
commitb279d67df88a49c6ca32b3eebd195660254be394 (patch)
tree41196a2c700ff2769692d2964e3f8e9de21b7000 /arch/x86/kernel/nmi.c
parentb7c4948e9881fb38b048269f376fb4bf194ce24a (diff)
downloadlinux-b279d67df88a49c6ca32b3eebd195660254be394.tar.xz
x86/nmi: Save regs in crash dump on external NMI
Now, multiple CPUs can receive an external NMI simultaneously by specifying the "apic_extnmi=all" command line parameter. When we take a crash dump by using external NMI with this option, we fail to save registers into the crash dump. This happens as follows: CPU 0 CPU 1 ================================ ============================= receive an external NMI default_do_nmi() receive an external NMI spin_lock(&nmi_reason_lock) default_do_nmi() io_check_error() spin_lock(&nmi_reason_lock) panic() busy loop ... kdump_nmi_shootdown_cpus() issue NMI IPI -----------> blocked until IRET busy loop... Here, since CPU 1 is in NMI context, an additional NMI from CPU 0 remains unhandled until CPU 1 IRETs. However, CPU 1 will never execute IRET so the NMI is not handled and the callback function to save registers is never called. To solve this issue, we check if the IPI for crash dumping was issued while waiting for nmi_reason_lock to be released, and if so, call its callback function directly. If the IPI is not issued (e.g. kdump is disabled), the actual behavior doesn't change. Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Baoquan He <bhe@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiang Liu <jiang.liu@linux.intel.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: kexec@lists.infradead.org Cc: linux-doc@vger.kernel.org Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stefan Lippers-Hollmann <s.l-h@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: x86-ml <x86@kernel.org> Link: http://lkml.kernel.org/r/20151210065245.4587.39316.stgit@softrs Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/nmi.c')
-rw-r--r--arch/x86/kernel/nmi.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 424aec4a4c71..8a2cdd736fa4 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -29,6 +29,7 @@
#include <asm/mach_traps.h>
#include <asm/nmi.h>
#include <asm/x86_init.h>
+#include <asm/reboot.h>
#define CREATE_TRACE_POINTS
#include <trace/events/nmi.h>
@@ -356,8 +357,19 @@ static void default_do_nmi(struct pt_regs *regs)
return;
}
- /* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
- raw_spin_lock(&nmi_reason_lock);
+ /*
+ * Non-CPU-specific NMI: NMI sources can be processed on any CPU.
+ *
+ * Another CPU may be processing panic routines while holding
+ * nmi_reason_lock. Check if the CPU issued the IPI for crash dumping,
+ * and if so, call its callback directly. If there is no CPU preparing
+ * crash dump, we simply loop here.
+ */
+ while (!raw_spin_trylock(&nmi_reason_lock)) {
+ run_crash_ipi_callback(regs);
+ cpu_relax();
+ }
+
reason = x86_platform.get_nmi_reason();
if (reason & NMI_REASON_MASK) {