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

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Date:	Sat, 25 Oct 2008 18:25:05 +0200
From:	"Carlos R. Mafra" <crmafra2@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	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 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) {
> +			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) {
> +			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))
> 
> -- 
> Arjan van de Ven 	Intel Open Source Technology Centre
> For development, discussion and tips for power savings, 
> visit http://www.lesswatts.org
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