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

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Message-ID: <20081025071348.63c426d9@infradead.org>
Date:	Sat, 25 Oct 2008 07:13:48 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	"Carlos R. Mafra" <crmafra2@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6.28-rc1 regression] wmifinfo dockapp takes 100% of cpu
 (bisected)

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?

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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