Re: [PATCH v3 2/3] autofs-5.1.1 - use monotonic clock for pthread cond timed wait.

[Ian Kent <raven@themaw.net>]

On Thu, 2015-09-17 at 11:48 +0800, Yu Ning wrote:
> The default PTHREAD_COND_INITIALIZER initializer uses realtime clock,
> we need to switch to use the monotic clock.
> 
> Signed-off-by: Yu Ning <ning.yu@ubuntu.com>
> ---
>  lib/alarm.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/alarm.c b/lib/alarm.c
> index 65a80ae..5b98b2d 100755
> --- a/lib/alarm.c
> +++ b/lib/alarm.c
> @@ -23,7 +23,7 @@ struct alarm {
>  };
>  
>  static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
> -static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
> +static pthread_cond_t cond;
>  static LIST_HEAD(alarms);
>  
>  #define alarm_lock() \
> @@ -212,6 +212,7 @@ int alarm_start_handler(void)
>  	pthread_t thid;
>  	pthread_attr_t attrs;
>  	pthread_attr_t *pattrs = &attrs;
> +	pthread_condattr_t condattrs;
>  	int status;
>  
>  	status = pthread_attr_init(pattrs);
> @@ -224,8 +225,18 @@ int alarm_start_handler(void)
>  #endif
>  	}
>  
> +	status = pthread_condattr_init(&condattrs);
> +	if (status)
> +		fatal(status);
> +
> +	pthread_condattr_setclock(&condattrs, CLOCK_MONOTONIC);
> +	pthread_cond_init(&cond, &condattrs);
> +
>  	status = pthread_create(&thid, pattrs, alarm_handler, NULL);
>  
> +	pthread_condattr_destroy(&condattrs);
> +	pthread_condattr_destroy(&cond);

I don't think we can do this.

The condition is used by the alarm_handler() for the duration of it's
life so I don't think we can't destroy its attributes after thread
creation.

In fact I'm not sure we even need the pthread_condattr_destroy(&cond)
but I'm not sure.

Destroying the condition attributes (condattrs) OTOH must not affect any
condition which it has been used to initialize so destroying that is
fine.

Let me have a closer look at this, maybe I've misunderstood what's going
on, and report back later.

> +
>  	if (pattrs)
>  		pthread_attr_destroy(pattrs);
>  


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