cpu plugin: Improve error message for host_processors() failing.

Issue: #22

diff --git a/src/cpu.c b/src/cpu.c
index 6753397..461a6e1 100644 (file)
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -146,15 +146,25 @@ static int init (void)
 
        port_host = mach_host_self ();
 
-       /* FIXME: Free `cpu_list' if it's not NULL */
-       if ((status = host_processors (port_host, &cpu_list, &cpu_list_len)) != KERN_SUCCESS)
+       status = host_processors (port_host, &cpu_list, &cpu_list_len);
+       if (status == KERN_INVALID_ARGUMENT)
        {
-               ERROR ("cpu plugin: host_processors returned %i", (int) status);
+               ERROR ("cpu plugin: Don't have a privileged host control port. "
+                               "The most common cause for this problem is "
+                               "that collectd is running without root "
+                               "privileges, which are required to read CPU "
+                               "load information. "
+                               "<https://collectd.org/bugs/22>");
+               cpu_list_len = 0;
+               return (-1);
+       }
+       if (status != KERN_SUCCESS)
+       {
+               ERROR ("cpu plugin: host_processors() failed with status %d.", (int) status);
                cpu_list_len = 0;
                return (-1);
        }
 
-       DEBUG ("host_processors returned %i %s", (int) cpu_list_len, cpu_list_len == 1 ? "processor" : "processors");
        INFO ("cpu plugin: Found %i processor%s.", (int) cpu_list_len, cpu_list_len == 1 ? "" : "s");
 /* #endif PROCESSOR_CPU_LOAD_INFO */
 
@@ -258,7 +268,7 @@ static int cpu_read (void)
        int cpu;
 
        kern_return_t status;
-       
+
        processor_cpu_load_info_data_t cpu_info;
        mach_msg_type_number_t         cpu_info_len;
 
@@ -512,10 +522,10 @@ static int cpu_read (void)
                        sstrerror (errno, errbuf, sizeof (errbuf)));
                return (-1);
        }
-       
-       if (pnumcpu != numcpu || perfcpu == NULL) 
+
+       if (pnumcpu != numcpu || perfcpu == NULL)
        {
-               if (perfcpu != NULL) 
+               if (perfcpu != NULL)
                        free(perfcpu);
                perfcpu = malloc(numcpu * sizeof(perfstat_cpu_t));
        }
@@ -530,7 +540,7 @@ static int cpu_read (void)
                return (-1);
        }
 
-       for (i = 0; i < cpus; i++) 
+       for (i = 0; i < cpus; i++)
        {
                submit (i, "idle",   (derive_t) perfcpu[i].idle);
                submit (i, "system", (derive_t) perfcpu[i].sys);