Messages in this thread Patch in this message | | | Subject | Re: [PATCH 4/4] futex: warning corrections | From | Vitaliy Ivanov <> | Date | Thu, 07 Jul 2011 00:11:09 +0300 |
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On Wed, 2011-07-06 at 10:00 -0700, Darren Hart wrote: > On 07/04/2011 04:21 PM, Vitaliy Ivanov wrote: > > From 3f7997d71fe2b5cb16e2913928f68023855d786d Mon Sep 17 00:00:00 2001 > > From: Vitaliy Ivanov <vitalivanov@gmail.com> > > Date: Tue, 5 Jul 2011 02:07:42 +0300 > > Subject: [PATCH 4/4] futex: warning corrections > Hi Vitaliy, > > Thanks for looking to fix these warnings. Note that the compiler isn't > always aware of some of the subtleties involved with things like > cmpxchg. In cases where it thinks there may be an uninitialized usage, > be sure to confirm it is possible before adding the overhead of an > assignment to a hot path. > > None of these assignments are necessary. Consider using __maybe_unused > instead.
Darren,
Actually unused and uninitialized are different issues. __maybe_unused won't help in this case but there is another trick used in kernel for this:
#define uninitialized_var(x) x = x
So, here is updated patch.
From 8eeaa5a97697bcc606aea23d32028aea7b271a96 Mon Sep 17 00:00:00 2001 From: Vitaliy Ivanov <vitalivanov@gmail.com> Date: Thu, 7 Jul 2011 00:05:05 +0300 Subject: [PATCH] futex: uninitialized warning corrections MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
kernel/futex.c: In function ‘fixup_pi_state_owner.clone.17’: kernel/futex.c:1582:6: warning: ‘curval’ may be used uninitialized in this function kernel/futex.c: In function ‘handle_futex_death’: kernel/futex.c:2486:6: warning: ‘nval’ may be used uninitialized in this function kernel/futex.c: In function ‘do_futex’: kernel/futex.c:863:11: warning: ‘curval’ may be used uninitialized in this function kernel/futex.c:828:6: note: ‘curval’ was declared here kernel/futex.c:898:5: warning: ‘oldval’ may be used uninitialized in this function kernel/futex.c:890:6: note: ‘oldval’ was declared here
Signed-off-by: Vitaliy Ivanov <vitalivanov@gmail.com> --- kernel/futex.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c index fe28dc2..efb8e5b 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -825,7 +825,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) { struct task_struct *new_owner; struct futex_pi_state *pi_state = this->pi_state; - u32 curval, newval; + u32 uninitialized_var(curval), newval; if (!pi_state) return -EINVAL; @@ -887,7 +887,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) static int unlock_futex_pi(u32 __user *uaddr, u32 uval) { - u32 oldval; + u32 uninitialized_var(oldval); /* * There is no waiter, so we unlock the futex. The owner died @@ -1546,7 +1546,7 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q, u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS; struct futex_pi_state *pi_state = q->pi_state; struct task_struct *oldowner = pi_state->owner; - u32 uval, curval, newval; + u32 uval, uninitialized_var(curval), newval; int ret; /* Owner died? */ @@ -2451,7 +2451,7 @@ err_unlock: */ int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi) { - u32 uval, nval, mval; + u32 uval, uninitialized_var(nval), mval; retry: if (get_user(uval, uaddr)) -- 1.7.4.1
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