Upgrade to 4.4.50-rt62

[kvmfornfv.git] / kernel / kernel / panic.c

diff --git a/kernel/kernel/panic.c b/kernel/kernel/panic.c
index 50d4ae2..3535f80 100644 (file)
--- a/kernel/kernel/panic.c
+++ b/kernel/kernel/panic.c
@@ -61,6 +61,37 @@ void __weak panic_smp_self_stop(void)
                cpu_relax();
 }
 
+/*
+ * Stop ourselves in NMI context if another CPU has already panicked. Arch code
+ * may override this to prepare for crash dumping, e.g. save regs info.
+ */
+void __weak nmi_panic_self_stop(struct pt_regs *regs)
+{
+       panic_smp_self_stop();
+}
+
+atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
+
+/*
+ * A variant of panic() called from NMI context. We return if we've already
+ * panicked on this CPU. If another CPU already panicked, loop in
+ * nmi_panic_self_stop() which can provide architecture dependent code such
+ * as saving register state for crash dump.
+ */
+void nmi_panic(struct pt_regs *regs, const char *msg)
+{
+       int old_cpu, cpu;
+
+       cpu = raw_smp_processor_id();
+       old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
+
+       if (old_cpu == PANIC_CPU_INVALID)
+               panic("%s", msg);
+       else if (old_cpu != cpu)
+               nmi_panic_self_stop(regs);
+}
+EXPORT_SYMBOL(nmi_panic);
+
 /**
  *     panic - halt the system
  *     @fmt: The text string to print
@@ -71,17 +102,17 @@ void __weak panic_smp_self_stop(void)
  */
 void panic(const char *fmt, ...)
 {
-       static DEFINE_SPINLOCK(panic_lock);
        static char buf[1024];
        va_list args;
        long i, i_next = 0;
        int state = 0;
+       int old_cpu, this_cpu;
 
        /*
         * Disable local interrupts. This will prevent panic_smp_self_stop
         * from deadlocking the first cpu that invokes the panic, since
         * there is nothing to prevent an interrupt handler (that runs
-        * after the panic_lock is acquired) from invoking panic again.
+        * after setting panic_cpu) from invoking panic() again.
         */
        local_irq_disable();
 
@@ -94,8 +125,16 @@ void panic(const char *fmt, ...)
         * multiple parallel invocations of panic, all other CPUs either
         * stop themself or will wait until they are stopped by the 1st CPU
         * with smp_send_stop().
+        *
+        * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
+        * comes here, so go ahead.
+        * `old_cpu == this_cpu' means we came from nmi_panic() which sets
+        * panic_cpu to this CPU.  In this case, this is also the 1st CPU.
         */
-       if (!spin_trylock(&panic_lock))
+       this_cpu = raw_smp_processor_id();
+       old_cpu  = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
+
+       if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
                panic_smp_self_stop();
 
        console_verbose();