[PATCH] fs/eventpoll.c: fix compilation warning

[PATCH] fs/eventpoll.c: fix compilation warning

[Viresh Kumar]

This patch fixes following compilation warning
fs/eventpoll.c:1119: warning: 'slack' may be used uninitialized in this function

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
---
 fs/eventpoll.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 8cf0724..c24a032 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1116,7 +1116,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 {
 	int res, eavail, timed_out = 0;
 	unsigned long flags;
-	long slack;
+	long slack = 0;
 	wait_queue_t wait;
 	struct timespec end_time;
 	ktime_t expires, *to = NULL;
-- 
1.7.2.2

Re: [PATCH] fs/eventpoll.c: fix compilation warning

[Jack Stone]

Viresh Kumar" <viresh.kumar@st.com> wrote:

>This patch fixes following compilation warning
>fs/eventpoll.c:1119: warning: 'slack' may be used uninitialized in this
>function
>
>Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
>---
> fs/eventpoll.c |    2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
>diff --git a/fs/eventpoll.c b/fs/eventpoll.c
>index 8cf0724..c24a032 100644
>--- a/fs/eventpoll.c
>+++ b/fs/eventpoll.c
>@@ -1116,7 +1116,7 @@ static int ep_poll(struct eventpoll *ep, struct
>epoll_event __user *events,
> {
> 	int res, eavail, timed_out = 0;
> 	unsigned long flags;
>-	long slack;
>+	long slack = 0;
> 	wait_queue_t wait;
> 	struct timespec end_time;
> 	ktime_t expires, *to = NULL;

I don't think this is the correct fix. This function is fine unless timeout is negative.

If a negative timeout is possible then this function will create timer far in the future. I'll leave it up to the maintainer how to solve that one. The two solutions I can see are making timeout unsigned or extending the bottom case of the if to <=0.

Either way we should use uninitalized_var() rather than setting it to zero.

Hope this makes sense,

Jack

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

Re: [PATCH] fs/eventpoll.c: fix compilation warning

[viresh kumar]

On 01/14/2011 03:03 PM, Jack Stone wrote:
>> >-	long slack;
>> >+	long slack = 0;
>> > 	wait_queue_t wait;
>> > 	struct timespec end_time;
>> > 	ktime_t expires, *to = NULL;
> I don't think this is the correct fix. This function is fine unless timeout is negative.
> 
> If a negative timeout is possible then this function will create timer far in the future.
>I'll leave it up to the maintainer how to solve that one. The two solutions I can see are making
>timeout unsigned or extending the bottom case of the if to <=0.
> 
> Either way we should use uninitalized_var() rather than setting it to zero.

Using uninitialized var gives compilation warning, How should we fix that.

-- 
viresh

Re: [PATCH] fs/eventpoll.c: fix compilation warning

[Jack Stone]

On 14/01/2011 09:38, viresh kumar wrote:
> On 01/14/2011 03:03 PM, Jack Stone wrote:
>>>> -	long slack;
>>>> +	long slack = 0;
>>>> 	wait_queue_t wait;
>>>> 	struct timespec end_time;
>>>> 	ktime_t expires, *to = NULL;
>> I don't think this is the correct fix. This function is fine unless timeout is negative.
>>
>> If a negative timeout is possible then this function will create timer far in the future.
>> I'll leave it up to the maintainer how to solve that one. The two solutions I can see are making
>> timeout unsigned or extending the bottom case of the if to <=0.
>>
>> Either way we should use uninitalized_var() rather than setting it to zero.
> 
> Using uninitialized var gives compilation warning, How should we fix that.
> 

I meant something like
-  long slack;
+  long uninitialized_var(slack);

I just had a go at generating this warning and couldn't. I've tried GCC
4.4.5 (From Fedora 13) and latest sparse.

Thanks,

Jack

Re: [PATCH] fs/eventpoll.c: fix compilation warning

[viresh kumar]

On 01/14/2011 04:25 PM, Jack Stone wrote:
> I meant something like
> -  long slack;
> +  long uninitialized_var(slack);

Thanks Jack,

That's new to me!!
I will resend it with suggested changes.

-- 
viresh