From: Gregory Herrero <gregory.herrero@oracle.com>
Date: Thu, 1 Jun 2017 08:53:04 +0000 (+0200)
Subject: stop_machine: fill fn_result only in case of error
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~2098
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success//%22http:/www.example.com/cgi/success/?a=commitdiff_plain;h=d8b833d78f6bfde9855a949b5e6d3790d78c0fb7;p=xen.git

stop_machine: fill fn_result only in case of error

When stop_machine_run() is called with NR_CPUS as last argument,
fn_result member must be filled only if an error happens since it is
shared across all cpus.

Assume CPU1 detects an error and set fn_result to -1, then CPU2 doesn't
detect an error and set fn_result to 0. The error detected by CPU1 will
be ignored.

Note that in case multiple failures occur on different CPUs, only the
last error will be reported.

Signed-off-by: Gregory Herrero <gregory.herrero@oracle.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
---

diff --git a/xen/common/stop_machine.c b/xen/common/stop_machine.c
index 304b783aae..ce6f5624c4 100644
--- a/xen/common/stop_machine.c
+++ b/xen/common/stop_machine.c
@@ -94,6 +94,7 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
     stopmachine_data.fn_data = data;
     stopmachine_data.nr_cpus = nr_cpus;
     stopmachine_data.fn_cpu = cpu;
+    stopmachine_data.fn_result = 0;
     atomic_set(&stopmachine_data.done, 0);
     stopmachine_data.state = STOPMACHINE_START;
 
@@ -112,7 +113,11 @@ int stop_machine_run(int (*fn)(void *), void *data, unsigned int cpu)
 
     stopmachine_set_state(STOPMACHINE_INVOKE);
     if ( (cpu == smp_processor_id()) || (cpu == NR_CPUS) )
-        stopmachine_data.fn_result = (*fn)(data);
+    {
+        ret = (*fn)(data);
+        if ( ret )
+            write_atomic(&stopmachine_data.fn_result, ret);
+    }
     stopmachine_wait_state();
     ret = stopmachine_data.fn_result;
 
@@ -150,8 +155,12 @@ static void stopmachine_action(unsigned long cpu)
         case STOPMACHINE_INVOKE:
             if ( (stopmachine_data.fn_cpu == smp_processor_id()) ||
                  (stopmachine_data.fn_cpu == NR_CPUS) )
-                stopmachine_data.fn_result =
-                    stopmachine_data.fn(stopmachine_data.fn_data);
+            {
+                int ret = stopmachine_data.fn(stopmachine_data.fn_data);
+
+                if ( ret )
+                    write_atomic(&stopmachine_data.fn_result, ret);
+            }
             break;
         default:
             break;