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Subject[PATCH 7/10] kdump: x86_64 kexec on panic


o 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:

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

o 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>
---
linux-2.6.15-rc1-1M-dynamic-root/arch/x86_64/kernel/crash.c | 86 +++++++++++-
1 files changed, 85 insertions(+), 1 deletion(-)
diff -puN arch/x86_64/kernel/crash.c~x86_64-kexec-on-panic arch/x86_64/kernel/crash.c
--- linux-2.6.15-rc1-1M-dynamic/arch/x86_64/kernel/crash.c~x86_64-kexec-on-panic 2005-11-17 11:11:10.000000000 +0530
+++ linux-2.6.15-rc1-1M-dynamic-root/arch/x86_64/kernel/crash.c 2005-11-17 11:54:15.000000000 +0530
@@ -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_re
* 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
+
}
_
-
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