[sheepdog] [PATCH v2] logger: avoid using SIGHUP for detecting death of sheep

[Liu Yuan]

On Tue, Jan 21, 2014 at 07:32:36PM +0900, Hitoshi Mitake wrote:
> It seems that current method of detecting sheep's death from logger
> process sometimes fails. The SIGHUP is caught as a request of log
> rotation.
> 
> The problem comes from that SIGHUP is used for both of log rotation
> request and death detection, and getppid() somestimes returns value
> not equal to 1 when SIGHUP which is caused by the death rises.
> 
> This patch lets logger detect death of sheep viapolling. The detection
> mechanism is simple: calling getppid() at the tail of the log flush
> loop every time. It would be enough for practical death detection.
> 
> Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
> ---
> 
> v2: simply break logger's loop when sheep dies
> 
>  lib/logger.c |   17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
> 
> diff --git a/lib/logger.c b/lib/logger.c
> index f855ab4..8be2bfd 100644
> --- a/lib/logger.c
> +++ b/lib/logger.c
> @@ -554,17 +554,6 @@ static void crash_handler(int signo)
>  
>  static void sighup_handler(int signo)
>  {
> -	if (getppid() == 1)
> -		/*
> -		 * My parent (sheep process) is dead. This SIGHUP is sent
> -		 * because of prctl(PR_SET_PDEATHSIG, SIGHUP)
> -		 */
> -		return crash_handler(signo);
> -
> -	/*
> -	 * My parent sheep process is still alive, this SIGHUP is a request
> -	 * for log rotation.
> -	*/
>  	rotate_log();
>  }
>  
> @@ -602,8 +591,6 @@ static void logger(char *log_dir, char *outfile)
>  	install_crash_handler(crash_handler);
>  	install_sighandler(SIGHUP, sighup_handler, false);
>  
> -	prctl(PR_SET_PDEATHSIG, SIGHUP);
> -
>  	/*
>  	 * we need to check the aliveness of the sheep process since
>  	 * it could die before the logger call prctl.
> @@ -631,6 +618,10 @@ static void logger(char *log_dir, char *outfile)
>  
>  		unblock_sighup();
>  
> +		if (getppid() == 1)
> +			/* My parent (sheep process) is dead. */
> +			break;
> +
>  		sleep(1);
>  	}
>  
> -- 
> 1.7.10.4
> 
> -- 
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> sheepdog at lists.wpkg.org

Applied thanks

Yuan