chcpu: provide better user feedback

Instead of printing error messages like "I/O resource busy" which are
supplied by strerror, give better feedback if the reason of failure
is known.
E.g. taking the last cpu offline cannot succeed, therefore print a
message that gives this "hint".

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

diff --git a/sys-utils/chcpu.c b/sys-utils/chcpu.c
index d4a25108c03b5c4f73967b9cb7032f70fd26d181..2cf015fb4b288e65d1530d65905caf4f85d0bdc3 100644 (file)
--- a/sys-utils/chcpu.c
+++ b/sys-utils/chcpu.c
@@ -42,9 +42,16 @@
 #include "path.h"
 
 #define _PATH_SYS_CPU          "/sys/devices/system/cpu"
+#define _PATH_SYS_CPU_ONLINE   _PATH_SYS_CPU "/online"
 #define _PATH_SYS_CPU_RESCAN   _PATH_SYS_CPU "/rescan"
 #define _PATH_SYS_CPU_DISPATCH _PATH_SYS_CPU "/dispatching"
 
+static cpu_set_t *onlinecpus;
+static size_t maxcpus;
+
+#define is_cpu_online(cpu) (CPU_ISSET_S((cpu), CPU_ALLOC_SIZE(maxcpus), onlinecpus))
+#define num_online_cpus()  (CPU_COUNT_S(CPU_ALLOC_SIZE(maxcpus), onlinecpus))
+
 enum {
        CMD_CPU_ENABLE  = 0,
        CMD_CPU_DISABLE,
@@ -59,6 +66,7 @@ static int cpu_enable(cpu_set_t *cpu_set, size_t setsize, int enable)
 {
        unsigned int cpu;
        int online, rc;
+       int configured = -1;
 
        for (cpu = 0; cpu < setsize; cpu++) {
                if (!CPU_ISSET(cpu, cpu_set))
@@ -80,20 +88,33 @@ static int cpu_enable(cpu_set_t *cpu_set, size_t setsize, int enable)
                        printf(_("CPU %d is already disabled\n"), cpu);
                        continue;
                }
+               if (path_exist(_PATH_SYS_CPU "/cpu%d/configure", cpu))
+                       configured = path_getnum(_PATH_SYS_CPU "/cpu%d/configure", cpu);
                if (enable) {
                        rc = path_writestr("1", _PATH_SYS_CPU "/cpu%d/online", cpu);
-                       if (rc == -1)
+                       if ((rc == -1) && (configured == 0))
+                               printf(_("CPU %d enable failed "
+                                        "(CPU is deconfigured)\n"), cpu);
+                       else if (rc == -1)
                                printf(_("CPU %d enable failed (%s)\n"), cpu,
                                        strerror(errno));
                        else
                                printf(_("CPU %d enabled\n"), cpu);
                } else {
+                       if (onlinecpus && num_online_cpus() == 1) {
+                               printf(_("CPU %d disable failed "
+                                        "(last enabled CPU)\n"), cpu);
+                               continue;
+                       }
                        rc = path_writestr("0", _PATH_SYS_CPU "/cpu%d/online", cpu);
                        if (rc == -1)
                                printf(_("CPU %d disable failed (%s)\n"), cpu,
                                        strerror(errno));
-                       else
+                       else {
                                printf(_("CPU %d disabled\n"), cpu);
+                               if (onlinecpus)
+                                       CPU_CLR(cpu, onlinecpus);
+                       }
                }
        }
        return EXIT_SUCCESS;
@@ -105,6 +126,7 @@ static int cpu_rescan(void)
                errx(EXIT_FAILURE, _("This system does not support rescanning of CPUs"));
        if (path_writestr("1", _PATH_SYS_CPU_RESCAN) == -1)
                err(EXIT_FAILURE, _("Failed to trigger rescan of CPUs"));
+       printf(_("Triggered rescan of CPUs\n"));
        return EXIT_SUCCESS;
 }
 
@@ -150,6 +172,12 @@ static int cpu_configure(cpu_set_t *cpu_set, size_t setsize, int configure)
                        printf(_("CPU %d is already deconfigured\n"), cpu);
                        continue;
                }
+               if ((current == 1) && (configure == 0) && onlinecpus &&
+                   is_cpu_online(cpu)) {
+                       printf(_("CPU %d deconfigure failed "
+                                "(CPU is enabled)\n"), cpu);
+                       continue;
+               }
                if (configure) {
                        rc = path_writestr("1", _PATH_SYS_CPU "/cpu%d/configure", cpu);
                        if (rc == -1)
@@ -203,7 +231,6 @@ static void __attribute__((__noreturn__)) usage(FILE *out)
 int main(int argc, char *argv[])
 {
        cpu_set_t *cpu_set;
-       unsigned int ncpus;
        size_t setsize;
        int cmd = -1;
        int c;
@@ -224,11 +251,13 @@ int main(int argc, char *argv[])
        bindtextdomain(PACKAGE, LOCALEDIR);
        textdomain(PACKAGE);
 
-       ncpus = get_max_number_of_cpus();
-       if (ncpus <= 0)
+       maxcpus = get_max_number_of_cpus();
+       if (maxcpus <= 0)
                errx(EXIT_FAILURE, _("cannot determine NR_CPUS; aborting"));
-       setsize = CPU_ALLOC_SIZE(ncpus);
-       cpu_set = CPU_ALLOC(ncpus);
+       if (path_exist(_PATH_SYS_CPU_ONLINE))
+               onlinecpus = path_cpulist(maxcpus, _PATH_SYS_CPU_ONLINE);
+       setsize = CPU_ALLOC_SIZE(maxcpus);
+       cpu_set = CPU_ALLOC(maxcpus);
        if (!cpu_set)
                err(EXIT_FAILURE, _("cpuset_alloc failed"));
 
@@ -282,13 +311,13 @@ int main(int argc, char *argv[])
 
        switch (cmd) {
        case CMD_CPU_ENABLE:
-               return cpu_enable(cpu_set, ncpus, 1);
+               return cpu_enable(cpu_set, maxcpus, 1);
        case CMD_CPU_DISABLE:
-               return cpu_enable(cpu_set, ncpus, 0);
+               return cpu_enable(cpu_set, maxcpus, 0);
        case CMD_CPU_CONFIGURE:
-               return cpu_configure(cpu_set, ncpus, 1);
+               return cpu_configure(cpu_set, maxcpus, 1);
        case CMD_CPU_DECONFIGURE:
-               return cpu_configure(cpu_set, ncpus, 0);
+               return cpu_configure(cpu_set, maxcpus, 0);
        case CMD_CPU_RESCAN:
                return cpu_rescan();
        case CMD_CPU_DISPATCH_HORIZONTAL: