Fix PR19241 by scanning for available CPUs.

Per PR19241/rhbz1280321, staprun was failing to start when CPU0
was offline or offline.  In bulk mode, staprun was failing if
any CPU but the last one was offline.  This patch fixes it by
scanning for available online CPUS up to NR_CPUS.

diff --git a/staprun/relay.c b/staprun/relay.c
index e994cdec9f6d88b9cbdbc92a8d55cade537234bb..f8edfd2560c1b1883239d90c4abd3ced91201fb6 100644 (file)
--- a/staprun/relay.c
+++ b/staprun/relay.c
@@ -15,6 +15,7 @@
 int out_fd[NR_CPUS];
 static pthread_t reader[NR_CPUS];
 static int relay_fd[NR_CPUS];
+static int avail_cpus[NR_CPUS];
 static int switch_file[NR_CPUS];
 static int bulkmode = 0;
 static volatile int stop_threads = 0;
@@ -215,14 +216,14 @@ static void switchfile_handler(int sig)
        if (stop_threads)
                return;
        for (i = 0; i < ncpus; i++)
-               if (reader[i] && switch_file[i]) {
+               if (reader[avail_cpus[i]] && switch_file[avail_cpus[i]]) {
                        dbug(2, "file switching is progressing, signal ignored.\n", sig);
                        return;
                }
        for (i = 0; i < ncpus; i++) {
-               if (reader[i]) {
-                       switch_file[i] = 1;
-                       pthread_kill(reader[i], SIGUSR2);
+               if (reader[avail_cpus[i]]) {
+                       switch_file[avail_cpus[i]] = 1;
+                       pthread_kill(reader[avail_cpus[i]], SIGUSR2);
                } else
                        break;
        }
@@ -236,6 +237,7 @@ static void switchfile_handler(int sig)
 int init_relayfs(void)
 {
        int i, len;
+       int cpui = 0;
        char rqbuf[128];
         char buf[PATH_MAX];
         struct sigaction sa;
@@ -250,10 +252,11 @@ int init_relayfs(void)
        if (send_request(STP_BULK, rqbuf, sizeof(rqbuf)) == 0)
                bulkmode = 1;
 
-        /* Try to open a slew of per-cpu trace%d files.  This will fail early;
-           for !bulkmode, it should pass only for "trace0"; for bulkmode,
-           it will fail at some actual-number-of-CPUs that we XXX hope is less
-           than NR_CPUS. */
+       /* Try to open a slew of per-cpu trace%d files.  Per PR19241, we
+          need to go through all potentially present CPUs up to NR_CPUS, that
+          we hope is a reasonable limit.  For !bulknode, "trace0" will be
+          typically used. */
+
        for (i = 0; i < NR_CPUS; i++) {
                 relay_fd[i] = -1;
 
@@ -272,11 +275,18 @@ int init_relayfs(void)
                         dbug(2, "attempting to open %s\n", buf);
                         relay_fd[i] = open(buf, O_RDONLY | O_NONBLOCK);
                 }
-               if (relay_fd[i] < 0 || set_clexec(relay_fd[i]) < 0)
-                       break;
+               if (relay_fd[i] >= 0) {
+                       avail_cpus[cpui++] = i;
+                       if (set_clexec(relay_fd[i]) < 0) {
+                               _err("failed to set FD_CLOEXEC on fd %d\n", i);
+                               return -1;
+                       }
+               }
        }
-       ncpus = i;
+       ncpus = cpui;
        dbug(2, "ncpus=%d, bulkmode = %d\n", ncpus, bulkmode);
+       for (i = 0; i < ncpus; i++)
+               dbug(2, "cpui=%d, relayfd=%d\n", i, avail_cpus[i]);
 
        if (ncpus == 0) {
                _err("couldn't open %s.\n", buf);
@@ -295,9 +305,9 @@ int init_relayfs(void)
        if (fsize_max) {
                /* switch file mode */
                for (i = 0; i < ncpus; i++) {
-                       if (init_backlog(i) < 0)
+                       if (init_backlog(avail_cpus[i]) < 0)
                                return -1;
-                       if (open_outfile(0, i, 0) < 0)
+                       if (open_outfile(0, avail_cpus[i], 0) < 0)
                                return -1;
                }
        } else if (bulkmode) {
@@ -317,20 +327,20 @@ int init_relayfs(void)
                                                return -1;
                                        }
                                        if (snprintf_chk(&buf[len],
-                                               PATH_MAX - len, "_%d", i))
+                                               PATH_MAX - len, "_%d", avail_cpus[i]))
                                                return -1;
                                }
                        } else {
-                               if (sprintf_chk(buf, "stpd_cpu%d", i))
+                               if (sprintf_chk(buf, "stpd_cpu%d", avail_cpus[i]))
                                        return -1;
                        }
                        
-                       out_fd[i] = open (buf, O_CREAT|O_TRUNC|O_WRONLY, 0666);
-                       if (out_fd[i] < 0) {
+                       out_fd[avail_cpus[i]] = open (buf, O_CREAT|O_TRUNC|O_WRONLY, 0666);
+                       if (out_fd[avail_cpus[i]] < 0) {
                                perr("Couldn't open output file %s", buf);
                                return -1;
                        }
-                       if (set_clexec(out_fd[i]) < 0)
+                       if (set_clexec(out_fd[avail_cpus[i]]) < 0)
                                return -1;
                }
        } else {
@@ -347,7 +357,7 @@ int init_relayfs(void)
                                perr("Couldn't open output file %s", buf);
                                return -1;
                        }
-                       if (set_clexec(out_fd[i]) < 0)
+                       if (set_clexec(out_fd[avail_cpus[i]]) < 0)
                                return -1;
                } else
                        out_fd[0] = STDOUT_FILENO;
@@ -361,8 +371,8 @@ int init_relayfs(void)
         sigaction(SIGUSR2, &sa, NULL);
         dbug(2, "starting threads\n");
         for (i = 0; i < ncpus; i++) {
-                if (pthread_create(&reader[i], NULL, reader_thread,
-                                   (void *)(long)i) < 0) {
+                if (pthread_create(&reader[avail_cpus[i]], NULL, reader_thread,
+                                   (void *)(long)avail_cpus[i]) < 0) {
                         _perr("failed to create thread");
                         return -1;
                 }
@@ -377,20 +387,20 @@ void close_relayfs(void)
        stop_threads = 1;
        dbug(2, "closing\n");
        for (i = 0; i < ncpus; i++) {
-               if (reader[i])
-                       pthread_kill(reader[i], SIGUSR2);
+               if (reader[avail_cpus[i]])
+                       pthread_kill(reader[avail_cpus[i]], SIGUSR2);
                else
                        break;
        }
        for (i = 0; i < ncpus; i++) {
-               if (reader[i])
-                       pthread_join(reader[i], NULL);
+               if (reader[avail_cpus[i]])
+                       pthread_join(reader[avail_cpus[i]], NULL);
                else
                        break;
        }
        for (i = 0; i < ncpus; i++) {
-               if (relay_fd[i] >= 0)
-                       close(relay_fd[i]);
+               if (relay_fd[avail_cpus[i]] >= 0)
+                       close(relay_fd[avail_cpus[i]]);
                else
                        break;
        }