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Message-ID: <47B73F0D.3090202@tiscali.nl>
Date: Sat, 16 Feb 2008 20:52:45 +0100
From: Roel Kluin <12o3l@...cali.nl>
To: "H. Peter Anvin" <hpa@...or.com>
CC: lkml <linux-kernel@...r.kernel.org>
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 <12o3l@...cali.nl>
---
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(¤t->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.
--
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