linux-kernel - Re: [PATCH 2.6.25-rc6] Fix itimer/many thread hang.

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Date:	Fri, 28 Mar 2008 11:28:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frank Mayhar <fmayhar@...gle.com>
Cc:	Roland McGrath <roland@...hat.com>, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2.6.25-rc6] Fix itimer/many thread hang.


* Frank Mayhar <fmayhar@...gle.com> wrote:

> +static inline void thread_group_times_init(struct signal_struct *sig)
> +{
> +	sig->thread_group_times = NULL;
> +}
> +
> +static inline void thread_group_times_free(struct signal_struct *sig)
> +{
> +	if (sig->thread_group_times)
> +		free_percpu(sig->thread_group_times);
> +}
> +
> +/*
> + * Allocate the thread_group_cputime struct appropriately and fill in the current
> + * values of the fields.  Called from do_setitimer() when setting an interval
> + * timer (ITIMER_PROF or ITIMER_VIRTUAL).  Assumes interrupts are enabled when
> + * it's called.  Note that there is no corresponding deallocation done from
> + * do_setitimer(); the structure is freed at process exit.
> + */
> +static inline int thread_group_times_alloc(struct task_struct *tsk)
> +{
> +	struct signal_struct *sig = tsk->signal;
> +	struct thread_group_cputime *thread_group_times;
> +	struct task_struct *t;
> +	cputime_t utime, stime;
> +	unsigned long long sum_exec_runtime;
> +
> +	/*
> +	 * If we don't already have a thread_group_cputime struct, allocate
> +	 * one and fill it in with the accumulated times.
> +	 */
> +	if (sig->thread_group_times)
> +		return 0;
> +	thread_group_times = alloc_percpu(struct thread_group_cputime);
> +	if (thread_group_times == NULL)
> +		return -ENOMEM;
> +	read_lock(&tasklist_lock);
> +	spin_lock_irq(&tsk->sighand->siglock);
> +	if (sig->thread_group_times) {
> +		spin_unlock_irq(&tsk->sighand->siglock);
> +		read_unlock(&tasklist_lock);
> +		free_percpu(thread_group_times);
> +		return 0;
> +	}
> +	sig->thread_group_times = thread_group_times;
> +	utime = sig->utime;
> +	stime = sig->stime;
> +	sum_exec_runtime = tsk->se.sum_exec_runtime;
> +	t = tsk;
> +	do {
> +		utime = cputime_add(utime, t->utime);
> +		stime = cputime_add(stime, t->stime);
> +		sum_exec_runtime += t->se.sum_exec_runtime;
> +	} while_each_thread(tsk, t);
> +	thread_group_times = per_cpu_ptr(sig->thread_group_times, get_cpu());
> +	thread_group_times->utime = utime;
> +	thread_group_times->stime = stime;
> +	thread_group_times->sum_exec_runtime = sum_exec_runtime;
> +	put_cpu_no_resched();
> +	spin_unlock_irq(&tsk->sighand->siglock);
> +	read_unlock(&tasklist_lock);
> +	return 0;
> +}

please dont put such a huge inline into a header.

> +
> +#define thread_group_update(sig, field, val, op) ({ \
> +	if (sig && sig->thread_group_times) {				\
> +		int cpu;						\
> +		struct thread_group_cputime *thread_group_times;	\
> +									\
> +		cpu = get_cpu();					\
> +		thread_group_times =					\
> +			per_cpu_ptr(sig->thread_group_times, cpu);	\
> +		thread_group_times->field =				\
> +			op(thread_group_times->field, val);		\
> +		put_cpu_no_resched();					\
> +	}								\
> +})

nor use any macros that includes code.

> +static inline int thread_group_cputime(struct thread_group_cputime *thread_group_times,
> +	struct signal_struct *sig)

ditto, line length as well.

> +	if (!sig->thread_group_times)
> +		return(0);

return 0 is the proper form - please run your patch through 
scripts/checkpatch.pl.

	Ingo
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