[PATCH] kdump: x86_64 kexec on panic

)

From: Vivek Goyal <vgoyal@in.ibm.com>

- Implementing the machine_crash_shutdown for x86_64 which will be called by
  crash_kexec (called in case of a panic, sysrq etc.).  Here we do things
  similar to i386.  Disable the interrupts, shootdown the cpus and shutdown
  LAPIC and IOAPIC.

Changes in this version:

- As the Eric's APIC initialization patches are reverted back, reintroducing
  LAPIC and IOAPIC shutdown.

- Added some comments on CPU hotplug, modified code as suggested by Andi
  kleen.

Signed-off-by: Murali M Chakravarthy <muralim@in.ibm.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 85 insertions, 1 deletions

diff --git a/arch/x86_64/kernel/crash.c b/arch/x86_64/kernel/crash.c
index efe450760bbc..abc601f36b6e 100644
--- a/arch/x86_64/kernel/crash.c
+++ b/arch/x86_64/kernel/crash.c
@@ -13,15 +13,85 @@
 #include <linux/smp.h>
 #include <linux/reboot.h>
 #include <linux/kexec.h>
+#include <linux/delay.h>
 
 #include <asm/processor.h>
 #include <asm/hardirq.h>
 #include <asm/nmi.h>
 #include <asm/hw_irq.h>
+#include <asm/mach_apic.h>
+
+/* This keeps a track of which one is crashing cpu. */
+static int crashing_cpu;
+
+#ifdef CONFIG_SMP
+static atomic_t waiting_for_crash_ipi;
+
+static int crash_nmi_callback(struct pt_regs *regs, int cpu)
+{
+        /*
+         * Don't do anything if this handler is invoked on crashing cpu.
+         * Otherwise, system will completely hang. Crashing cpu can get
+         * an NMI if system was initially booted with nmi_watchdog parameter.
+         */
+        if (cpu == crashing_cpu)
+                return 1;
+        local_irq_disable();
+
+        disable_local_APIC();
+        atomic_dec(&waiting_for_crash_ipi);
+        /* Assume hlt works */
+        for(;;)
+                asm("hlt");
+
+        return 1;
+}
+
+static void smp_send_nmi_allbutself(void)
+{
+        send_IPI_allbutself(APIC_DM_NMI);
+}
+
+/*
+ * This code is a best effort heuristic to get the
+ * other cpus to stop executing. So races with
+ * cpu hotplug shouldn't matter.
+ */
+
+static void nmi_shootdown_cpus(void)
+{
+        unsigned long msecs;
+
+        atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+        set_nmi_callback(crash_nmi_callback);
+
+        /*
+         * Ensure the new callback function is set before sending
+         * out the NMI
+         */
+        wmb();
+
+        smp_send_nmi_allbutself();
+
+        msecs = 1000; /* Wait at most a second for the other cpus to stop */
+        while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
+                mdelay(1);
+                msecs--;
+        }
+        /* Leave the nmi callback set */
+        disable_local_APIC();
+}
+#else
+static void nmi_shootdown_cpus(void)
+{
+        /* There are no cpus to shootdown */
+}
+#endif
 
 void machine_crash_shutdown(struct pt_regs *regs)
 {
-        /* This function is only called after the system
+        /*
+         * This function is only called after the system
          * has paniced or is otherwise in a critical state.
          * The minimum amount of code to allow a kexec'd kernel
          * to run successfully needs to happen here.
@@ -29,4 +99,18 @@ void machine_crash_shutdown(struct pt_regs *regs)
          * In practice this means shooting down the other cpus in
          * an SMP system.
          */
+        /* The kernel is broken so disable interrupts */
+        local_irq_disable();
+
+        /* Make a note of crashing cpu. Will be used in NMI callback.*/
+        crashing_cpu = smp_processor_id();
+        nmi_shootdown_cpus();
+
+        if(cpu_has_apic)
+                 disable_local_APIC();
+
+#if defined(CONFIG_X86_IO_APIC)
+        disable_IO_APIC();
+#endif
+
 }