From owner-freebsd-hackers  Tue Nov 21  6: 5:13 2000
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Date: Tue, 21 Nov 2000 17:06:05 +0300 (MSK)
Reply-To: diwil@dataart.com
From: Dmitry Dicky <diwil@dataart.com>
To: Vladimir Terziev <vladimirt@rila.bg>
Subject: RE: Semaphore blocking and signal handling
Cc: hackers@FreeBSD.ORG
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Hi, 
easy:

-------------------------------
extern int errno;

int sem_lock(int semnumb)
{
   struct sembuf sb[2];

   sb[0].sem_num = semnumb;
   sb[0].sem_op = -1;
   sb[0].sem_flg = 0;
again:
   if( semop(sh->sem, sb,1) )
   {
      errmsg("Semaphore %d erorr: %s\n",sh->sem, strerror(errno));
       // here you'll see the reason why semaphore returned an error 
      if(errno = EINTR) goto again;
      return -1;
   }
   return 0;
}
----------------------------------

At least it works in my case.

Regards,
D.



On 21-Nov-00 Vladimir Terziev wrote:
> Hi.
> 
> Am I right for the following:
> 
> When a process is blocked on semop (trying to get resource) and receives
> a signal (for which the process has a handler), the process gets
> unblocked
> from the semop wait (to handle the signal), and after handling the
> signal
> continues with the instruction after semop, as if it was unblocked by
> successful semop.
> 
> Is this behaviour normal, and is there a way for the process to
> distinguish
> between signal handling unblock and successful semop operation (may be
> by
> setting a global variable in the signal-handling function) ?
> 
> Thank you in advance.
> 
> Vladimir Terziev
> 
> 
> 
> 
> To Unsubscribe: send mail to majordomo@FreeBSD.org
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