[Xen-devel] Re: [Xen-changelog] Make xenstored reopen its trace file on SIGHUP. This allows one to rotate the

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Xen patchbot -unstable wrote:

> +void reopen_log()
> +{
> +       if (!tracefile)
> +               return;
> +
> +       if (tracefd > 0)
> +               close(tracefd);
> +       tracefd = open(tracefile, O_WRONLY|O_CREAT|O_APPEND, 0600);
> +       if (tracefd < 0) {
> +               perror("Could not open tracefile");
> +               return;
> +       }
> +       write(tracefd, "\n***\n", strlen("\n***\n"));
> +}
> +
>  
perror and strlen are not safe to call from a signal handler.

I suggest just removing the perror call altogether and replacing strlen 
with sizeof() - 1.
Regards,

Anthony Liguori

> static bool write_messages(struct connection *conn)
> {
>         int ret;
> @@ -1498,11 +1514,7 @@
>                         outputpid = true;
>                         break;
>                 case 'T':
> -                       tracefd = open(optarg, O_WRONLY|O_CREAT|O_APPEND, 0600);
> -                       if (tracefd < 0)
> -                               barf_perror("Could not open tracefile %s",
> -                                           optarg);
> -                        write(tracefd, "\n***\n", strlen("\n***\n"));
> +                       tracefile = optarg;
>                         break;
>                 case 'V':
>                         verbose = true;
> @@ -1511,6 +1523,8 @@
>         }
>         if (optind != argc)
>                 barf("%s: No arguments desired", argv[0]);
> +
> +       reopen_log();
>
>         if (dofork) {
>                 openlog("xenstored", 0, LOG_DAEMON);
> @@ -1577,6 +1591,8 @@
>                 close(STDOUT_FILENO);
>                 close(STDERR_FILENO);
>         }
> +
> +       signal(SIGHUP, reopen_log);
>
> #ifdef TESTING
>         signal(SIGUSR1, stop_failtest);
>
> _______________________________________________
> Xen-changelog mailing list
> Xen-changelog@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-changelog
>
>  

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