Re: [PATCH 20/40] mn10300: Use set_current_blocked() andblock_sigmask()

[Matt Fleming]

On Tue, 2012-02-14 at 15:56 +0000, David Howells wrote:
> Matt Fleming <matt@xxxxxxxxxxxxxxxxx> wrote:
> 
> >  asmlinkage long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
> >  {
> > -	mask &= _BLOCKABLE;
> > -	spin_lock_irq(&current->sighand->siglock);
> > +	sigset_t blocked;
> > +
> >  	current->saved_sigmask = current->blocked;
> 
> Can this line create a race, now that it's not protected by a lock?  It is
> possible for current->blocked to get altered by another thread.

->blocked can only ever be altered by current, not another thread. See
the following comment from sigprocmask() in kernel/signal.c,

       /* Lockless, only current can change ->blocked, never from irq */
        if (oldset)                                                                                      
                *oldset = tsk->blocked;                                                                  

-- 
Matt Fleming, Intel Open Source Technology Center

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