linux-kernel - Re: [2.6.28-rc1 regression] wmifinfo dockapp takes 100% of cpu (bisected)

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Date:	Sat, 25 Oct 2008 20:03:27 +0200
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	"Carlos R. Mafra" <crmafra2@...il.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6.28-rc1 regression] wmifinfo dockapp takes 100% of cpu
	(bisected)

On Sat, Oct 25, 2008 at 06:25:05PM +0200, Carlos R. Mafra wrote:
> On Sat 25.Oct'08 at  7:13:48 -0700, Arjan van de Ven wrote:
> > On Sat, 25 Oct 2008 07:05:42 -0700
> > Arjan van de Ven <arjan@...ux.intel.com> wrote:
> > 
> > > Carlos R. Mafra wrote:
> > > 
> > > 
> > > Hi,
> > > 
> > > the line below is the key one:
> > > 
> > > > select(4, [3], NULL, NULL, {0, 5000000}) = -1 EINVAL (Invalid
> > > > argument)
> > > 
> > > the application gives us an invalid timeval; it should have been (5,
> > > 0) However, if the kernel accepted this before the kernel needs to
> > > now also accept it obviously, I'll look into it
> > 
> > This patch should fix it; I'm a bit worried that I need to fix up
> > userlands "mess", but ok. I also checked all other converted functions,
> > and only select has this problem. The problem is that the conversion
> > from microseconds to nanoseconds is overflowing ;-(
> > 
> > can you give this one a test?
> 
> Your patch did not solve it.
> 
> But you are right that the program I use is a mess, it was doing
> 
>     tv.tv_sec = 0;
>     tv.tv_usec = 5000000L;
> 
> So I changed it to
> 
>     tv.tv_sec = 5;
>     tv.tv_usec = 0;
> 
> and it worked (with and without your patch).
> 
> From what I understand this is what your patch does,
> so it is strange that it didn't work...
> 
> > diff --git a/fs/compat.c b/fs/compat.c
> > index fe3c9bf..95ceee6 100644
> > --- a/fs/compat.c
> > +++ b/fs/compat.c
> > @@ -1680,9 +1680,16 @@ asmlinkage long compat_sys_select(int n, compat_ulong_t __user *inp,
> >  	int ret;
> >  
> >  	if (tvp) {
> > +		int i;
> >  		if (copy_from_user(&tv, tvp, sizeof(tv)))
> >  			return -EFAULT;
> >  
> > +		while (tv.tv_usec > USEC_PER_SEC && i < 1000) {
                                  ^ 
should be >=

> > +			i++;
> > +			tv.tv_sec ++;
> > +			tv.tv_usec -= USEC_PER_SEC;
> > +		}
> > +
> >  		to = &end_time;
> >  		if (poll_select_set_timeout(to, tv.tv_sec,
> >  					    tv.tv_usec * NSEC_PER_USEC))
> > diff --git a/fs/select.c b/fs/select.c
> > index 448e440..e4e7cdb 100644
> > --- a/fs/select.c
> > +++ b/fs/select.c
> > @@ -515,9 +515,16 @@ asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
> >  	int ret;
> >  
> >  	if (tvp) {
> > +		int i = 0;
> >  		if (copy_from_user(&tv, tvp, sizeof(tv)))
> >  			return -EFAULT;
> >  
> > +		while (tv.tv_usec > USEC_PER_SEC && i < 1000) {

and here too

> > +			i++;
> > +			tv.tv_sec ++;
> > +			tv.tv_usec -= USEC_PER_SEC;
> > +		}
> > +
> >  		to = &end_time;
> >  		if (poll_select_set_timeout(to, tv.tv_sec,
> >  					    tv.tv_usec * NSEC_PER_USEC))
> > 
> > -- 
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