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Subject[PATCH] getdelays.c
File: Documentation/accounting/getdelays.c

Linux version: 2.6.25-4

Description:

This patch adds a USR1 signal handler to getdelays.c, which causes
getdelays to close its logfile and reopen it (if '-w logfile' is
specified). This is useful in situations when getdelays is running for
a long time (i.e, the log file growing) and you need to rotate the
logs but don't want to lose any log data.


Sample usage:

1 # ./getdelays -m0,1,2,3 -l -w getdelays.log &
(time passes)
2 # mv getdelays.log getdelays.log.1
3 # kill -USR1 <getdelays pid>

line 1: starts the program
line 2: renames the logfile. The log descriptor is still open and data
being written to the log (assuming we didn't cross mountpoints)
line 3: getdelays closes the old descriptor and reopens getdelays.log


Note on 'volatile' usage:

I know this is generally frowned on, but I think it's needed here to
avoid the compiler optimizing away the variable (it will appear as if
it's never called, since it's value only changes in the signal
handler).


Patch:
<patch>
--- getdelays.c 2008-05-15 09:00:12.000000000 -0600
+++ getdelays.c 2008-06-05 02:23:57.000000000 -0600
@@ -50,6 +50,7 @@ int dbg;
int print_delays;
int print_io_accounting;
int print_task_context_switch_counts;
+volatile sig_atomic_t reopen_log = 0;
__u64 stime, utime;

#define PRINTF(fmt, arg...) { \
@@ -80,6 +81,7 @@ static void usage(void)
fprintf(stderr, " -l: listen forever\n");
fprintf(stderr, " -v: debug on\n");
fprintf(stderr, " -C: container path\n");
+ fprintf(stderr, "\nSend USR1 to reopen the logfile if -w is used.\n");
}

/*
@@ -231,6 +233,30 @@ void print_ioacct(struct taskstats *t)
(unsigned long long)t->cancelled_write_bytes);
}

+void catch_usr1(int sig)
+{
+ reopen_log = 1;
+ signal(sig, catch_usr1);
+}
+
+int reopen_logfile(int fd, char *logfile)
+{
+ if (fd) {
+ PRINTF("USR1 received. Closing logfile.\n");
+ close(fd);
+ }
+ fd = open(logfile, O_WRONLY | O_CREAT | O_TRUNC,
+ S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+ if (fd == -1) {
+ perror("Cannot open output file\n");
+ exit(1);
+ }
+
+ reopen_log = 0;
+
+ return fd;
+}
+
int main(int argc, char *argv[])
{
int c, rc, rep_len, aggr_len, len2, cmd_type;
@@ -320,12 +346,8 @@ int main(int argc, char *argv[])
}

if (write_file) {
- fd = open(logfile, O_WRONLY | O_CREAT | O_TRUNC,
- S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
- if (fd == -1) {
- perror("Cannot open output file\n");
- exit(1);
- }
+ fd = reopen_logfile(fd, logfile);
+ signal(SIGUSR1, catch_usr1); /* only set when write_file is set */
}

if ((nl_sd = create_nl_socket(NETLINK_GENERIC)) < 0)
@@ -444,6 +466,9 @@ int main(int argc, char *argv[])
err(1,"write error\n");
}
}
+ if (reopen_log) {
+ fd = reopen_logfile(fd, logfile);
+ }
if (!loop)
goto done;
break;
</patch>
Scott
--
Scott Wiersdorf
<scott@perlcode.org>


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