Re: [PATCH] hackbench: init child's struct before using it

[Clark Williams <williams@redhat.com>]

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Applied to my work branch for the next release. I've CC'd John Kacur
who has been doing the heavy lifting on rt-tests recently.

Clark

On Thu, 11 Apr 2013 17:20:05 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> Commit ad27df7 ("Reimplement better child tracking and improve error
> handling") changed the way of reporting pid/error after creating a
> child. It will return an union which is a mix pid_t, pthread_t and a
> signed long long for errors.
> Now on 32bit x86 both pid_t and pthread_t are four byte in size and are
> stored in the first 4 bytes. Now if the most significant bit of the long
> long variable happens to be set by chance (because nobody really
> initializes the variable here) then error variable will be negative. On
> little endian machines the assignment of pid or threadid won't reset the
> sign bit and you see this:
> 
> | Running in process mode with 10 groups using 40 file descriptors each (== 400 tasks)
> | Each sender will pass 100 messages of 100 bytes
> | 0 children started.  Expected 40
> | sending SIGTERM to all child processes
> | signaling 0 worker threads to terminate
> | Creating workers (error: Success)
> 
> A machine with proper endian handlig (that is big endian) would reset
> the sign bit during the assignment of pid and I would not have to make
> this patch :)
> 
> While here, I make create_worker() since it is not used outside of this
> file.
> 
> Cc: David Sommerseth <davids@redhat.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  src/hackbench/hackbench.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/src/hackbench/hackbench.c b/src/hackbench/hackbench.c
> index 8baeb23..c21b4db 100644
> --- a/src/hackbench/hackbench.c
> +++ b/src/hackbench/hackbench.c
> @@ -189,13 +189,14 @@ static void *receiver(struct receiver_context* ctx)
>  	return NULL;
>  }
>  
> -childinfo_t create_worker(void *ctx, void *(*func)(void *))
> +static childinfo_t create_worker(void *ctx, void *(*func)(void *))
>  {
>  	pthread_attr_t attr;
>  	int err;
>  	childinfo_t child;
>  	pid_t childpid;
>  
> +	memset(&child, 0, sizeof(child));
>  	switch (process_mode) {
>  	case PROCESS_MODE: /* process mode */
>  		/* Fork the sender/receiver child. */
> -- 
> 1.7.10.4
> 

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