iowatcher: Convert start_blktrace to run_program

Rework start_blktrace and use run_program to launch blktrace. Move the
argv-building into the function so that it's easier to work with and
clean it up a bit. Add a signal parameter to wait_program to optionally
kill the pid with a given signal before waiting for it.

Signed-off-by: Andrew Price <anprice@redhat.com>

diff --git a/iowatcher/tracers.c b/iowatcher/tracers.c
index 4844deb482663cb1780e67db82ba04ba2d681914..6ecf24ce4ce2c9faaf3ed8a69ecf3af72b37a1d0 100644 (file)
--- a/iowatcher/tracers.c
+++ b/iowatcher/tracers.c
@@ -46,26 +46,12 @@ static char line[1024];
 static pid_t blktrace_pid = 0;
 static pid_t mpstat_pid = 0;
 
-char *blktrace_args[17 + MAX_DEVICES_PER_TRACE * 2] = {
-       "blktrace",
-       "-b", "8192",
-       "-a", "queue",
-       "-a", "complete",
-       "-a", "issue",
-       "-a", "notify",
-       "-D", ".",
-       NULL,
-};
-
 char *mpstat_args[] = {
        "mpstat",
        "-P", "ALL", "1",
        NULL,
 };
 
-#define DEST_DIR_INDEX 12
-#define LAST_ARG 13
-
 int stop_tracer(pid_t *tracer_pid)
 {
        int ret;
@@ -90,91 +76,82 @@ int stop_tracer(pid_t *tracer_pid)
        return 0;
 }
 
-
-void stop_all_tracers(void)
+static void sig_handler_for_quit(int val)
 {
-       stop_tracer(&blktrace_pid);
+       fprintf(stderr, "Received signal %d. Terminating tracers.\n", val);
+       if (blktrace_pid) {
+               wait_program(blktrace_pid, "blktrace", SIGTERM);
+               blktrace_pid = 0;
+       }
        stop_tracer(&mpstat_pid);
 }
 
-void sig_handler_for_quit(int val)
-{
-       fprintf(stderr, "iowatcher exiting with %d, stopping tracers\n", val);
-       stop_all_tracers();
-}
-
-
 int start_blktrace(char **devices, int num_devices, char *trace_name, char *dest)
 {
-       pid_t pid;
        int ret;
-       char **arg = blktrace_args;
        int i;
-       int arg_index;
+       char *argv[15 + MAX_DEVICES_PER_TRACE * 2];
+       int argc = 0;
 
-       fprintf(stderr, "running blktrace");
        if (!trace_name)
                trace_name = "trace";
+       if (!dest)
+               dest = ".";
+
+       argv[argc++] = "blktrace";
+       argv[argc++] = "-b";
+       argv[argc++] = "8192";
+       argv[argc++] = "-a";
+       argv[argc++] = "queue";
+       argv[argc++] = "-a";
+       argv[argc++] = "complete";
+       argv[argc++] = "-a";
+       argv[argc++] = "issue";
+       argv[argc++] = "-a";
+       argv[argc++] = "notify";
 
-       arg_index = LAST_ARG;
-       for (i = 0; i < num_devices; i++) {
-               blktrace_args[arg_index++] = "-d";
-               blktrace_args[arg_index++] = devices[i];
-       }
-
-       /*
-        * single device traces use -o and are put into
-        * the dest dir if provided
-        */
        if (num_devices == 1) {
-               blktrace_args[arg_index++] = "-o";
-               blktrace_args[arg_index++] = trace_name;
-               if (dest)
-                       blktrace_args[DEST_DIR_INDEX] = dest;
+               argv[argc++] = "-o";
+               argv[argc++] = trace_name;
        } else {
-               /*
-                * multi device traces are put into a dest
-                * dir based on the trace name
-                */
-               blktrace_args[DEST_DIR_INDEX] = trace_name;
+               /* Multiple devices output to a directory named trace_name */
+               dest = trace_name;
        }
+       argv[argc++] = "-D";
+       argv[argc++] = dest;
 
-       blktrace_args[arg_index] = NULL;
-
-       while(*arg) {
-               fprintf(stderr, " %s", *arg);
-               arg++;
-       }
-       fprintf(stderr, "\n");
-
-
-       pid = fork();
-       if (pid == 0) {
-               ret = execvp("blktrace", blktrace_args);
-               if (ret) {
-                       fprintf(stderr, "failed to exec blktrace error %s\n", strerror(errno));
-                       exit(errno);
-               }
-
-       } else {
-               blktrace_pid = pid;
-               signal(SIGTERM, sig_handler_for_quit);
-               signal(SIGINT, sig_handler_for_quit);
+       for (i = 0; i < num_devices; i++) {
+               argv[argc++] = "-d";
+               argv[argc++] = devices[i];
        }
-       return 0;
+       argv[argc] = NULL;
+       signal(SIGTERM, sig_handler_for_quit);
+       signal(SIGINT, sig_handler_for_quit);
+       ret = run_program(argc, argv, 0, &blktrace_pid);
+       return ret;
 }
 
-int wait_program(pid_t pid, const char *pname)
+int wait_program(pid_t pid, const char *pname, int sig)
 {
        int status;
        int ret = 0;
 
+       if (sig) {
+               ret = kill(pid, sig);
+               if (ret) {
+                       fprintf(stderr, "Failed to send signal %d to %s (%lu): %s\n",
+                               sig, pname, (long)pid, strerror(errno));
+                       return ret;
+               }
+               fprintf(stderr, "Kill (%d): %s (%ld)\n", sig, pname, (long)pid);
+       }
+
        waitpid(pid, &status, 0);
        if (WIFEXITED(status)) {
                ret = WEXITSTATUS(status);
                if (ret == 127) /* spawnp failed after forking */
                        fprintf(stderr, "Failed to run '%s'\n", pname);
-       } else if (WIFSIGNALED(status)) {
+       } else if (WIFSIGNALED(status) && sig && WTERMSIG(status) != sig) {
                fprintf(stderr, "'%s' killed by signal %d\n", pname, WTERMSIG(status));
                ret = -1;
        }
@@ -196,7 +173,7 @@ int run_program(int argc, char **argv, int wait, pid_t *pid)
        if (err != 0) {
                fprintf(stderr, "Could not run '%s': %s\n", argv[0], strerror(err));
        } else if (wait) {
-               err = wait_program(_pid, argv[0]);
+               err = wait_program(_pid, argv[0], 0);
        } else if (!pid) {
                fprintf(stderr, "Warning: %s (%ld): Not saving pid and not waiting for it.\n",
                        argv[0], (long)_pid);
@@ -208,13 +185,15 @@ int run_program(int argc, char **argv, int wait, pid_t *pid)
 
 int wait_for_tracers(void)
 {
-       int status = 0;
-       stop_all_tracers();
        if (blktrace_pid != 0) {
-               waitpid(blktrace_pid, &status, WUNTRACED);
+               int err = wait_program(blktrace_pid, "blktrace", SIGINT);
+               if (err)
+                       exit(1);
                blktrace_pid = 0;
        }
        if (mpstat_pid != 0) {
+               int status = 0;
+               stop_tracer(&mpstat_pid);
                waitpid(mpstat_pid, &status, WUNTRACED);
                mpstat_pid = 0;
        }

diff --git a/iowatcher/tracers.h b/iowatcher/tracers.h
index ed57f5de33b6cd9a82b130e68ee05cd22f3f2f08..77c31a6d69f9aa6a29661f4349e269fd956ed95d 100644 (file)
--- a/iowatcher/tracers.h
+++ b/iowatcher/tracers.h
@@ -18,7 +18,7 @@
 #ifndef __IOWATCH_TRACERS
 #define __IOWATCH_TRACERS
 int run_program(int argc, char **argv, int wait, pid_t *pid);
-int wait_program(pid_t pid, const char *pname);
+int wait_program(pid_t pid, const char *pname, int signal);
 int stop_blktrace(void);
 int start_blktrace(char **devices, int num_devices, char *trace_name, char *dest);
 int start_mpstat(char *trace_name);