[Xen-changelog] [xen stable-4.3] x86/crash: Indicate how well nmi_shootdown_cpus() managed to do

[patchbot@xxxxxxx]

commit 39b9a5bc0858b604560499afdc9964a670c8b67b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Jan 17 16:31:50 2014 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jan 17 16:31:50 2014 +0100

    x86/crash: Indicate how well nmi_shootdown_cpus() managed to do
    
    Having nmi_shootdown_cpus() report which pcpus failed to be shot down is a
    useful debugging hint as to what possibly went wrong (especially when the
    crash logs seem to indicate that an NMI timeout occurred while waiting for 
one
    of the problematic pcpus to perform an action).
    
    This is achieved by swapping an atomic_t count of unreported pcpus with a
    cpumask.  In the case that the 1 second timeout occurs, use the cpumask to
    identify the problematic pcpus.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Keir Fraser <keir@xxxxxxx>
    master commit: f12c1f0b09205cdf18a2c4a615fdc3e7357ce704
    master date: 2013-09-26 10:14:51 +0200
---
 xen/arch/x86/crash.c |   19 +++++++++++++++----
 1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/crash.c b/xen/arch/x86/crash.c
index b692e91..01fd906 100644
--- a/xen/arch/x86/crash.c
+++ b/xen/arch/x86/crash.c
@@ -22,6 +22,7 @@
 #include <xen/perfc.h>
 #include <xen/kexec.h>
 #include <xen/sched.h>
+#include <xen/keyhandler.h>
 #include <public/xen.h>
 #include <asm/shared.h>
 #include <asm/hvm/support.h>
@@ -30,7 +31,7 @@
 #include <xen/iommu.h>
 #include <asm/hpet.h>
 
-static atomic_t waiting_for_crash_ipi;
+static cpumask_t waiting_to_crash;
 static unsigned int crashing_cpu;
 static DEFINE_PER_CPU_READ_MOSTLY(bool_t, crash_save_done);
 
@@ -65,7 +66,7 @@ void __attribute__((noreturn)) do_nmi_crash(struct 
cpu_user_regs *regs)
         __stop_this_cpu();
 
         this_cpu(crash_save_done) = 1;
-        atomic_dec(&waiting_for_crash_ipi);
+        cpumask_clear_cpu(cpu, &waiting_to_crash);
     }
 
     /* Poor mans self_nmi().  __stop_this_cpu() has reverted the LAPIC
@@ -123,7 +124,7 @@ static void nmi_shootdown_cpus(void)
     crashing_cpu = cpu;
     local_irq_count(crashing_cpu) = 0;
 
-    atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+    cpumask_andnot(&waiting_to_crash, &cpu_online_map, cpumask_of(cpu));
 
     /* Change NMI trap handlers.  Non-crashing pcpus get nmi_crash which
      * invokes do_nmi_crash (above), which cause them to write state and
@@ -163,12 +164,22 @@ static void nmi_shootdown_cpus(void)
     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 )
+    while ( !cpumask_empty(&waiting_to_crash) && msecs )
     {
         mdelay(1);
         msecs--;
     }
 
+    /* Leave a hint of how well we did trying to shoot down the other cpus */
+    if ( cpumask_empty(&waiting_to_crash) )
+        printk("Shot down all CPUs\n");
+    else
+    {
+        cpulist_scnprintf(keyhandler_scratch, sizeof keyhandler_scratch,
+                          &waiting_to_crash);
+        printk("Failed to shoot down CPUs {%s}\n", keyhandler_scratch);
+    }
+
     /* Crash shutdown any IOMMU functionality as the crashdump kernel is not
      * happy when booting if interrupt/dma remapping is still enabled */
     iommu_crash_shutdown();
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.3

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