svn commit: r292019 - head/usr.sbin/iostat

[Alan Somers]

Author: asomers
Date: Wed Dec  9 18:07:26 2015
New Revision: 292019
URL: https://svnweb.freebsd.org/changeset/base/292019

Log:
  When iostat(8) receives SIGINT while running with "-w" or "-c", it will now
  print statistics one more time before exiting. Also, it now implements the
  wait using setitimer instead of sleep, so the waits will be more consistent
  when the system is heavily loaded.
  
  MFC after:	4 weeks
  Sponsored by:	Spectra Logic Corp
  Differential Revision:	https://reviews.freebsd.org/D4473

Modified:
  head/usr.sbin/iostat/iostat.c

Modified: head/usr.sbin/iostat/iostat.c
==============================================================================
--- head/usr.sbin/iostat/iostat.c	Wed Dec  9 13:45:51 2015	(r292018)
+++ head/usr.sbin/iostat/iostat.c	Wed Dec  9 18:07:26 2015	(r292019)
@@ -110,6 +110,7 @@
 #include <limits.h>
 #include <math.h>
 #include <nlist.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -135,6 +136,8 @@ struct device_selection *dev_select;
 int maxshowdevs;
 volatile sig_atomic_t headercount;
 volatile sig_atomic_t wresized;		/* Tty resized, when non-zero. */
+volatile sig_atomic_t alarm_rang;
+volatile sig_atomic_t return_requested;
 unsigned short wrows;			/* Current number of tty rows. */
 int dflag = 0, Iflag = 0, Cflag = 0, Tflag = 0, oflag = 0, Kflag = 0;
 int xflag = 0, zflag = 0;
@@ -143,6 +146,8 @@ int xflag = 0, zflag = 0;
 static void usage(void);
 static void needhdr(int signo);
 static void needresize(int signo);
+static void needreturn(int signo);
+static void alarm_clock(int signo);
 static void doresize(void);
 static void phdr(void);
 static void devstats(int perf_select, long double etime, int havelast);
@@ -172,6 +177,7 @@ main(int argc, char **argv)
 	int count = 0, waittime = 0;
 	char *memf = NULL, *nlistf = NULL;
 	struct devstat_match *matches;
+	struct itimerval alarmspec;
 	int num_matches = 0;
 	char errbuf[_POSIX2_LINE_MAX];
 	kvm_t *kd = NULL;
@@ -442,10 +448,28 @@ main(int argc, char **argv)
 		wrows = IOSTAT_DEFAULT_ROWS;
 	}
 
+	/*
+	 * Register a SIGINT handler so that we can print out final statistics
+	 * when we get that signal
+	 */
+	(void)signal(SIGINT, needreturn);
+
+	/*
+	 * Register a SIGALRM handler to implement sleeps if the user uses the
+	 * -c or -w options
+	 */
+	(void)signal(SIGALRM, alarm_clock);
+	alarmspec.it_interval.tv_sec = waittime / 1000;
+	alarmspec.it_interval.tv_usec = 1000 * (waittime % 1000);
+	alarmspec.it_value.tv_sec = waittime / 1000;
+	alarmspec.it_value.tv_usec = 1000 * (waittime % 1000);
+	setitimer(ITIMER_REAL, &alarmspec, NULL);
+
 	for (headercount = 1;;) {
 		struct devinfo *tmp_dinfo;
 		long tmp;
 		long double etime;
+		sigset_t sigmask, oldsigmask;
 
 		if (Tflag > 0) {
 			if ((readvar(kd, "kern.tty_nin", X_TTY_NIN, &cur.tk_nin,
@@ -599,10 +623,23 @@ main(int argc, char **argv)
 		}
 		fflush(stdout);
 
-		if (count >= 0 && --count <= 0)
+		if ((count >= 0 && --count <= 0) || return_requested)
 			break;
 
-		usleep(waittime * 1000);
+		/*
+		 * Use sigsuspend to safely sleep until either signal is
+		 * received
+		 */
+		alarm_rang = 0;
+		sigemptyset(&sigmask);
+		sigaddset(&sigmask, SIGINT);
+		sigaddset(&sigmask, SIGALRM);
+		sigprocmask(SIG_BLOCK, &sigmask, &oldsigmask);
+		while (! (alarm_rang || return_requested) ) {
+			sigsuspend(&oldsigmask);
+		}
+		sigprocmask(SIG_UNBLOCK, &sigmask, NULL);
+
 		havelast = 1;
 	}
 
@@ -633,6 +670,24 @@ needresize(int signo)
 }
 
 /*
+ * Record the alarm so the main loop can break its sleep
+ */
+void
+alarm_clock(int signo)
+{
+	alarm_rang = 1;
+}
+
+/*
+ * Request that the main loop exit soon
+ */
+void
+needreturn(int signo)
+{
+	return_requested = 1;
+}
+
+/*
  * Update the global `wrows' count of terminal rows.
  */
 void