2008-02-16 15:58:22

by Roel Kluin

[permalink] [raw]
Subject: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

Not entirely sure who to send this to
---
Replace !likely(x) by likely(!x)

Signed-off-by: Roel Kluin <[email protected]>
---
diff --git a/kernel/exit.c b/kernel/exit.c
index 506a957..df207fc 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1497,7 +1497,7 @@ repeat:
/*
* We don't reap group leaders with subthreads.
*/
- if (!likely(options & WEXITED))
+ if (likely(!(options & WEXITED)))
continue;
retval = wait_task_zombie(p,
(options & WNOWAIT), infop,
@@ -1508,7 +1508,7 @@ repeat:
* exit, stop, or stop and then continue.
*/
flag = 1;
- if (!unlikely(options & WCONTINUED))
+ if (unlikely(!(options & WCONTINUED)))
continue;
retval = wait_task_continued(p,
(options & WNOWAIT), infop,
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 7c2118f..b42254b 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -36,7 +36,7 @@ static inline int freezeable(struct task_struct * p)
*/
static inline void frozen_process(void)
{
- if (!unlikely(current->flags & PF_NOFREEZE)) {
+ if (unlikely(!(current->flags & PF_NOFREEZE))) {
current->flags |= PF_FROZEN;
wmb();
}
diff --git a/kernel/signal.c b/kernel/signal.c
index 84917fe..1155e16 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1308,7 +1308,7 @@ int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
*/
rcu_read_lock();

- if (!likely(lock_task_sighand(p, &flags))) {
+ if (likely(!lock_task_sighand(p, &flags))) {
ret = -1;
goto out_err;
}
@@ -1548,7 +1548,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)

static inline int may_ptrace_stop(void)
{
- if (!likely(current->ptrace & PT_PTRACED))
+ if (likely(!(current->ptrace & PT_PTRACED)))
return 0;
/*
* Are we in the middle of do_coredump?
@@ -1574,7 +1574,7 @@ static int sigkill_pending(struct task_struct *tsk)
{
return ((sigismember(&tsk->pending.signal, SIGKILL) ||
sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
- !unlikely(sigismember(&tsk->blocked, SIGKILL)));
+ unlikely(!sigismember(&tsk->blocked, SIGKILL)));
}

/*
@@ -1625,7 +1625,7 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
spin_unlock_irq(&current->sighand->siglock);
try_to_freeze();
read_lock(&tasklist_lock);
- if (!unlikely(killed) && may_ptrace_stop()) {
+ if (unlikely(!killed) && may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
read_unlock(&tasklist_lock);
schedule();
@@ -1717,7 +1717,7 @@ static int do_signal_stop(int signr)
} else {
struct task_struct *t;

- if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
+ if (likely(!(sig->flags & SIGNAL_STOP_DEQUEUED)) ||
unlikely(sig->group_exit_task))
return 0;
/*


2008-02-16 19:01:54

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

Roel Kluin wrote:
> Not entirely sure who to send this to
> ---
> Replace !likely(x) by likely(!x)

Whoa...

Are you sure this is correct?

!likely(x) is equivalent to unlikely(!x), not the opposite, so this is a
functional change...

-hpa

2008-02-16 19:30:01

by Roel Kluin

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

H. Peter Anvin wrote:
> Roel Kluin wrote:
>> Not entirely sure who to send this to
>> ---
>> Replace !likely(x) by likely(!x)
>
> Whoa...
>
> Are you sure this is correct?
>
> !likely(x) is equivalent to unlikely(!x), not the opposite, so this is a
> functional change...
>
> -hpa
>
You are right, sorry, Need more caffeine. I will send the right patch later.

2008-02-16 19:32:00

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

Roel Kluin wrote:
> H. Peter Anvin wrote:
>> Roel Kluin wrote:
>>> Not entirely sure who to send this to
>>> ---
>>> Replace !likely(x) by likely(!x)
>> Whoa...
>>
>> Are you sure this is correct?
>>
>> !likely(x) is equivalent to unlikely(!x), not the opposite, so this is a
>> functional change...
>>
> You are right, sorry, Need more caffeine. I will send the right patch later.

Note I didn't say it was wrong, I just wanted a bit more explanation
about why it's right, if it is.

-hpa

2008-02-16 19:52:59

by Roel Kluin

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

H. Peter Anvin wrote:
> Roel Kluin wrote:
>> H. Peter Anvin wrote:
>>> Roel Kluin wrote:
>>>> Not entirely sure who to send this to
>>>> ---
>>>> Replace !likely(x) by likely(!x)
>>> Whoa...
>>>
>>> Are you sure this is correct?
>>>
>>> !likely(x) is equivalent to unlikely(!x), not the opposite, so this is a
>>> functional change...
>>>
>> You are right, sorry, Need more caffeine. I will send the right patch
>> later.
>
> Note I didn't say it was wrong, I just wanted a bit more explanation
> about why it's right, if it is.

No, I just wanted to move the '!' within the parentheses, I didn't want
to change semantics. below is how I guess the patch should have been.
Thanks for your response.
---
Replace !likely(x) by unlikely(!x)

Signed-off-by: Roel Kluin <[email protected]>
---
diff --git a/kernel/signal.c b/kernel/signal.c
index 84917fe..cf5d45a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1308,7 +1308,7 @@ int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
*/
rcu_read_lock();

- if (!likely(lock_task_sighand(p, &flags))) {
+ if (unlikely(!lock_task_sighand(p, &flags))) {
ret = -1;
goto out_err;
}
@@ -1548,7 +1548,7 @@ static void do_notify_parent_cldstop(struct task_struct *tsk, int why)

static inline int may_ptrace_stop(void)
{
- if (!likely(current->ptrace & PT_PTRACED))
+ if (unlikely(!(current->ptrace & PT_PTRACED)))
return 0;
/*
* Are we in the middle of do_coredump?
@@ -1574,7 +1574,7 @@ static int sigkill_pending(struct task_struct *tsk)
{
return ((sigismember(&tsk->pending.signal, SIGKILL) ||
sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
- !unlikely(sigismember(&tsk->blocked, SIGKILL)));
+ likely(!sigismember(&tsk->blocked, SIGKILL)));
}

/*
@@ -1625,7 +1625,7 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
spin_unlock_irq(&current->sighand->siglock);
try_to_freeze();
read_lock(&tasklist_lock);
- if (!unlikely(killed) && may_ptrace_stop()) {
+ if (likely(!killed) && may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
read_unlock(&tasklist_lock);
schedule();
@@ -1717,8 +1717,8 @@ static int do_signal_stop(int signr)
} else {
struct task_struct *t;

- if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
- unlikely(sig->group_exit_task))
+ if (unlikely(!(sig->flags & SIGNAL_STOP_DEQUEUED) ||
+ sig->group_exit_task))
return 0;
/*
* There is no group stop already in progress.

2008-02-17 02:31:49

by Rene Herman

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

On 16-02-08 20:01, H. Peter Anvin wrote:
> Roel Kluin wrote:
>> Not entirely sure who to send this to
>> ---
>> Replace !likely(x) by likely(!x)
>
> Whoa...
>
> Are you sure this is correct?
>
> !likely(x) is equivalent to unlikely(!x)

Not with respect to its value I believe? likely(x) == !!(x), and
unlikely(!x) == !!(!x) = !x, so conditions work out differently?

> not the opposite, so this is a functional change...

Rene.

2008-02-17 03:57:14

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

Rene Herman wrote:
> On 16-02-08 20:01, H. Peter Anvin wrote:
>> Roel Kluin wrote:
>>> Not entirely sure who to send this to
>>> ---
>>> Replace !likely(x) by likely(!x)
>>
>> Whoa...
>>
>> Are you sure this is correct?
>>
>> !likely(x) is equivalent to unlikely(!x)
>
> Not with respect to its value I believe? likely(x) == !!(x), and
> unlikely(!x) == !!(!x) = !x, so conditions work out differently?

You missed one ! sign:

!likely(x) == !!!(x) == unlikely(!x) == !!(!(x))

-hpa

2008-02-17 04:14:23

by Rene Herman

[permalink] [raw]
Subject: Re: [PATCH 2/2] kernel/{exit.c, signal.c, power/process.c}: replace !likely(x) by likely(!x)

On 17-02-08 04:56, H. Peter Anvin wrote:

> Rene Herman wrote:
>> On 16-02-08 20:01, H. Peter Anvin wrote:
>>> Roel Kluin wrote:
>>>> Not entirely sure who to send this to
>>>> ---
>>>> Replace !likely(x) by likely(!x)
>>>
>>> Whoa...
>>>
>>> Are you sure this is correct?
>>>
>>> !likely(x) is equivalent to unlikely(!x)
>>
>> Not with respect to its value I believe? likely(x) == !!(x), and
>> unlikely(!x) == !!(!x) = !x, so conditions work out differently?
>
> You missed one ! sign:
>
> !likely(x) == !!!(x) == unlikely(!x) == !!(!(x))

Yup, sorry, misread.

Rene.