From: Serge Pavlovsky <pal@interexc.com>
To: ALT Linux Sisyphus discussion list <sisyphus@altlinux.ru>
Subject: Re: [sisyphus] Работа под 2.6.х с привязкой ко временным отметкам.
Date: Mon, 11 Oct 2004 03:27:16 +0300
Message-ID: <1097454436.2793.0.camel@underdark.interexc.com> (raw)
In-Reply-To: <200410081748.07275.serpiph@nikiet.ru>
It is not safe to call mutex functions from a signal handler. In
particular, calling `pthread_mutex_lock' or `pthread_mutex_unlock' from
a signal handler may deadlock the calling thread.
On Птн, 2004-10-08 at 17:48 +0400, Epiphanov Sergei wrote:
> Есть программа, которую решил привязать к таймеру для работы в реальном
> времени. Принцип простой: поставил обработку setitimer на запуск SIG_ALARM
> с шагом 10 мсек.
>
> #define _XOPEN_SOURCE 600
> #define _GNU_SOURCE
> #include <sys/time.h>
> #include <signal.h>
> #include <stdio.h>
> #include <pthread.h>
>
>
>
> volatile int nextnum=0;
> volatile pthread_mutex_t fastmutex;
>
> void alarmsig(int i){
> pthread_mutex_lock( &fastmutex );
> nextnum++;
> pthread_mutex_unlock( &fastmutex );
> }
>
> static struct sigaction oldsig;
>
> /*type<0.5 - drop timer
> type>0.5 - set timer*/
> void settimer_(float *type, float *step){
> long int sec = *step;
> long int usec = (*step-sec)*1e6;
> struct itimerval tv,old;
> struct sigaction newsig,temp;
> pthread_mutexattr_t attr;
> printf("sec=%ld usec=%ld\n",sec,usec);
> if( *type>0.5 ){
> pthread_mutexattr_init( &attr );
> pthread_mutexattr_settype( &attr, PTHREAD_MUTEX_FAST_NP );
> pthread_mutex_init( &fastmutex, &attr );
> pthread_mutexattr_destroy( &attr );
> tv.it_interval.tv_sec = sec;
> tv.it_interval.tv_usec = usec;
> tv.it_value.tv_sec = sec;
> tv.it_value.tv_usec = usec;
> nextnum = 0;
> newsig.sa_handler = alarmsig;
> newsig.sa_flags = SA_NOMASK;
> sigaction( SIGALRM, &newsig, &oldsig );
> setitimer( ITIMER_REAL, &tv, &old );
> } else{
> tv.it_interval.tv_sec = 0;
> tv.it_interval.tv_usec = 0;
> tv.it_value.tv_sec = 0;
> tv.it_value.tv_usec = 0;
> setitimer( ITIMER_REAL, &tv, &old );
> nextnum = 0;
> sigaction( SIGALRM, &oldsig, &temp );
> pthread_mutex_destroy( &fastmutex );
> }
>
> }
>
> void waittime_( float *err ){
> int cur = nextnum;
> if( cur>1 ){
> *err = cur;
> return;
> }
> while( !cur ){
> pthread_mutex_lock( &fastmutex );
> cur = nextnum;
> pthread_mutex_unlock( &fastmutex );
> }
> *err = 0;
> pthread_mutex_lock( &fastmutex );
> nextnum = 0;
> pthread_mutex_unlock( &fastmutex );
> return;
> }
>
> Затем:
> 1)t=0
> 2)в цикле:
> а) основная программа
> б) t=t+10мсек
> в) waittime_(err)
> г) завершение цикла при t>=100сек.
>
> Так вот, при таком раскладе на ядре 2.6.8-std-smp-alt9 программа работает
> 110сек (+10%). И этот расклад не зависит от шага (10мсек, 100мсек, 1сек).
> На ядре 2.4.26-std-up-alt6 эта же программа без пересборки работает точно
> 100 сек. Что это может быть?
>
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next prev parent reply other threads:[~2004-10-11 0:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-08 13:48 Epiphanov Sergei
2004-10-11 0:27 ` Serge Pavlovsky [this message]
2004-10-11 7:42 ` Epiphanov Sergei
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