linux-kernel - Re: [PATCH 1/4] copy_signal cleanup: use zalloc and remove initializations

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Date:	Wed, 2 Dec 2009 14:57:59 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Veaceslav Falico <vfalico@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	Miloslav Trmac <mitr@...hat.com>,
	James Morris <jmorris@...ei.org>,
	Alan Cox <alan@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Renaud Lottiaux <renaud.lottiaux@...labs.com>,
	Louis Rilling <louis.rilling@...labs.com>,
	David Howells <dhowells@...hat.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>
Subject: Re: [PATCH 1/4] copy_signal cleanup: use zalloc and remove
	initializations

On 12/01, Veaceslav Falico wrote:
>
> Use kmem_cache_zalloc() on signal creation and remove unneeded initialization
> lines.

I like this series very much. Not only it cleanups and lessens the code,
it opens the possibility to do more cleanups. Say, we can simplify
exit_notify() a bit, we can remove ->group_exit_task check since we know
->notify_count < 0 can be false positive.

A couple of nits though,

> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
> ---
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 166b8c4..160477d 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -825,17 +825,6 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
>  	/* Thread group counters. */
>  	thread_group_cputime_init(sig);
>
> -	/* Expiration times and increments. */
> -	sig->it[CPUCLOCK_PROF].expires = cputime_zero;
> -	sig->it[CPUCLOCK_PROF].incr = cputime_zero;
> -	sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
> -	sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
> -
> -	/* Cached expiration times. */
> -	sig->cputime_expires.prof_exp = cputime_zero;
> -	sig->cputime_expires.virt_exp = cputime_zero;
> -	sig->cputime_expires.sched_exp = 0;
> -
>  	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
>  		sig->cputime_expires.prof_exp =
>  			secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);

Personally I don't mind, but perhaps it is better to move this change
into 3/4 which changes thread_group_cputime_init().

> @@ -855,7 +844,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
>  	if (clone_flags & CLONE_THREAD)
>  		return 0;
>
> -	sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
> +	sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
>
> [...snip...]

Imho, very nice change.

Oleg.

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