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Date:   Sat, 2 Sep 2017 19:56:36 +0200
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Anna-Maria Gleixner <anna-maria@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, keescook@...omium.org,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-can@...r.kernel.org
Subject: Re: [PATCH 19/25] can/bcm: Replace hrtimer_tasklet with softirq based
 hrtimer

On 08/31/2017 02:23 PM, Anna-Maria Gleixner wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> Switch the timer to CLOCK_MONOTONIC_SOFT, which executed the timer
> callback in softirq context and remove the hrtimer_tasklet.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
> Cc: Oliver Hartkopp <socketcan@...tkopp.net>

Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>

Thanks,
Oliver

> Cc: Marc Kleine-Budde <mkl@...gutronix.de>
> Cc: linux-can@...r.kernel.org
> ---
>   net/can/bcm.c |  150 ++++++++++++++++++----------------------------------------
>   1 file changed, 49 insertions(+), 101 deletions(-)
> 
> --- a/net/can/bcm.c
> +++ b/net/can/bcm.c
> @@ -102,7 +102,6 @@ struct bcm_op {
>   	unsigned long frames_abs, frames_filtered;
>   	struct bcm_timeval ival1, ival2;
>   	struct hrtimer timer, thrtimer;
> -	struct tasklet_struct tsklet, thrtsklet;
>   	ktime_t rx_stamp, kt_ival1, kt_ival2, kt_lastmsg;
>   	int rx_ifindex;
>   	int cfsiz;
> @@ -364,25 +363,34 @@ static void bcm_send_to_user(struct bcm_
>   	}
>   }
>   
> -static void bcm_tx_start_timer(struct bcm_op *op)
> +static bool bcm_tx_set_expiry(struct bcm_op *op, struct hrtimer *hrt)
>   {
> +	ktime_t ival;
> +
>   	if (op->kt_ival1 && op->count)
> -		hrtimer_start(&op->timer,
> -			      ktime_add(ktime_get(), op->kt_ival1),
> -			      HRTIMER_MODE_ABS);
> +		ival = op->kt_ival1;
>   	else if (op->kt_ival2)
> -		hrtimer_start(&op->timer,
> -			      ktime_add(ktime_get(), op->kt_ival2),
> -			      HRTIMER_MODE_ABS);
> +		ival = op->kt_ival2;
> +	else
> +		return false;
> +
> +	hrtimer_set_expires(hrt, ktime_add(ktime_get(), ival));
> +	return true;
>   }
>   
> -static void bcm_tx_timeout_tsklet(unsigned long data)
> +static void bcm_tx_start_timer(struct bcm_op *op)
>   {
> -	struct bcm_op *op = (struct bcm_op *)data;
> +	if (bcm_tx_set_expiry(op, &op->timer))
> +		hrtimer_start_expires(&op->timer, HRTIMER_MODE_ABS);
> +}
> +
> +/* bcm_tx_timeout_handler - performs cyclic CAN frame transmissions */
> +static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
> +{
> +	struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
>   	struct bcm_msg_head msg_head;
>   
>   	if (op->kt_ival1 && (op->count > 0)) {
> -
>   		op->count--;
>   		if (!op->count && (op->flags & TX_COUNTEVT)) {
>   
> @@ -399,22 +407,12 @@ static void bcm_tx_timeout_tsklet(unsign
>   		}
>   		bcm_can_tx(op);
>   
> -	} else if (op->kt_ival2)
> +	} else if (op->kt_ival2) {
>   		bcm_can_tx(op);
> +	}
>   
> -	bcm_tx_start_timer(op);
> -}
> -
> -/*
> - * bcm_tx_timeout_handler - performs cyclic CAN frame transmissions
> - */
> -static enum hrtimer_restart bcm_tx_timeout_handler(struct hrtimer *hrtimer)
> -{
> -	struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
> -
> -	tasklet_schedule(&op->tsklet);
> -
> -	return HRTIMER_NORESTART;
> +	return bcm_tx_set_expiry(op, &op->timer) ?
> +		HRTIMER_RESTART : HRTIMER_NORESTART;
>   }
>   
>   /*
> @@ -542,11 +540,18 @@ static void bcm_rx_starttimer(struct bcm
>   		hrtimer_start(&op->timer, op->kt_ival1, HRTIMER_MODE_REL);
>   }
>   
> -static void bcm_rx_timeout_tsklet(unsigned long data)
> +/* bcm_rx_timeout_handler - when the (cyclic) CAN frame reception timed out */
> +static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
>   {
> -	struct bcm_op *op = (struct bcm_op *)data;
> +	struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
>   	struct bcm_msg_head msg_head;
>   
> +	/* if user wants to be informed, when cyclic CAN-Messages come back */
> +	if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
> +		/* clear received CAN frames to indicate 'nothing received' */
> +		memset(op->last_frames, 0, op->nframes * op->cfsiz);
> +	}
> +
>   	/* create notification to user */
>   	msg_head.opcode  = RX_TIMEOUT;
>   	msg_head.flags   = op->flags;
> @@ -557,25 +562,6 @@ static void bcm_rx_timeout_tsklet(unsign
>   	msg_head.nframes = 0;
>   
>   	bcm_send_to_user(op, &msg_head, NULL, 0);
> -}
> -
> -/*
> - * bcm_rx_timeout_handler - when the (cyclic) CAN frame reception timed out
> - */
> -static enum hrtimer_restart bcm_rx_timeout_handler(struct hrtimer *hrtimer)
> -{
> -	struct bcm_op *op = container_of(hrtimer, struct bcm_op, timer);
> -
> -	/* schedule before NET_RX_SOFTIRQ */
> -	tasklet_hi_schedule(&op->tsklet);
> -
> -	/* no restart of the timer is done here! */
> -
> -	/* if user wants to be informed, when cyclic CAN-Messages come back */
> -	if ((op->flags & RX_ANNOUNCE_RESUME) && op->last_frames) {
> -		/* clear received CAN frames to indicate 'nothing received' */
> -		memset(op->last_frames, 0, op->nframes * op->cfsiz);
> -	}
>   
>   	return HRTIMER_NORESTART;
>   }
> @@ -583,14 +569,12 @@ static enum hrtimer_restart bcm_rx_timeo
>   /*
>    * bcm_rx_do_flush - helper for bcm_rx_thr_flush
>    */
> -static inline int bcm_rx_do_flush(struct bcm_op *op, int update,
> -				  unsigned int index)
> +static inline int bcm_rx_do_flush(struct bcm_op *op, unsigned int index)
>   {
>   	struct canfd_frame *lcf = op->last_frames + op->cfsiz * index;
>   
>   	if ((op->last_frames) && (lcf->flags & RX_THR)) {
> -		if (update)
> -			bcm_rx_changed(op, lcf);
> +		bcm_rx_changed(op, lcf);
>   		return 1;
>   	}
>   	return 0;
> @@ -598,11 +582,8 @@ static inline int bcm_rx_do_flush(struct
>   
>   /*
>    * bcm_rx_thr_flush - Check for throttled data and send it to the userspace
> - *
> - * update == 0 : just check if throttled data is available  (any irq context)
> - * update == 1 : check and send throttled data to userspace (soft_irq context)
>    */
> -static int bcm_rx_thr_flush(struct bcm_op *op, int update)
> +static int bcm_rx_thr_flush(struct bcm_op *op)
>   {
>   	int updated = 0;
>   
> @@ -611,24 +592,16 @@ static int bcm_rx_thr_flush(struct bcm_o
>   
>   		/* for MUX filter we start at index 1 */
>   		for (i = 1; i < op->nframes; i++)
> -			updated += bcm_rx_do_flush(op, update, i);
> +			updated += bcm_rx_do_flush(op, i);
>   
>   	} else {
>   		/* for RX_FILTER_ID and simple filter */
> -		updated += bcm_rx_do_flush(op, update, 0);
> +		updated += bcm_rx_do_flush(op, 0);
>   	}
>   
>   	return updated;
>   }
>   
> -static void bcm_rx_thr_tsklet(unsigned long data)
> -{
> -	struct bcm_op *op = (struct bcm_op *)data;
> -
> -	/* push the changed data to the userspace */
> -	bcm_rx_thr_flush(op, 1);
> -}
> -
>   /*
>    * bcm_rx_thr_handler - the time for blocked content updates is over now:
>    *                      Check for throttled data and send it to the userspace
> @@ -637,9 +610,7 @@ static enum hrtimer_restart bcm_rx_thr_h
>   {
>   	struct bcm_op *op = container_of(hrtimer, struct bcm_op, thrtimer);
>   
> -	tasklet_schedule(&op->thrtsklet);
> -
> -	if (bcm_rx_thr_flush(op, 0)) {
> +	if (bcm_rx_thr_flush(op)) {
>   		hrtimer_forward(hrtimer, ktime_get(), op->kt_ival2);
>   		return HRTIMER_RESTART;
>   	} else {
> @@ -735,23 +706,8 @@ static struct bcm_op *bcm_find_op(struct
>   
>   static void bcm_remove_op(struct bcm_op *op)
>   {
> -	if (op->tsklet.func) {
> -		while (test_bit(TASKLET_STATE_SCHED, &op->tsklet.state) ||
> -		       test_bit(TASKLET_STATE_RUN, &op->tsklet.state) ||
> -		       hrtimer_active(&op->timer)) {
> -			hrtimer_cancel(&op->timer);
> -			tasklet_kill(&op->tsklet);
> -		}
> -	}
> -
> -	if (op->thrtsklet.func) {
> -		while (test_bit(TASKLET_STATE_SCHED, &op->thrtsklet.state) ||
> -		       test_bit(TASKLET_STATE_RUN, &op->thrtsklet.state) ||
> -		       hrtimer_active(&op->thrtimer)) {
> -			hrtimer_cancel(&op->thrtimer);
> -			tasklet_kill(&op->thrtsklet);
> -		}
> -	}
> +	hrtimer_cancel(&op->timer);
> +	hrtimer_cancel(&op->thrtimer);
>   
>   	if ((op->frames) && (op->frames != &op->sframe))
>   		kfree(op->frames);
> @@ -979,15 +935,13 @@ static int bcm_tx_setup(struct bcm_msg_h
>   		op->ifindex = ifindex;
>   
>   		/* initialize uninitialized (kzalloc) structure */
> -		hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +		hrtimer_init(&op->timer, CLOCK_MONOTONIC_SOFT,
> +			     HRTIMER_MODE_REL);
>   		op->timer.function = bcm_tx_timeout_handler;
>   
> -		/* initialize tasklet for tx countevent notification */
> -		tasklet_init(&op->tsklet, bcm_tx_timeout_tsklet,
> -			     (unsigned long) op);
> -
>   		/* currently unused in tx_ops */
> -		hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +		hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC_SOFT,
> +			     HRTIMER_MODE_REL);
>   
>   		/* add this bcm_op to the list of the tx_ops */
>   		list_add(&op->list, &bo->tx_ops);
> @@ -1150,20 +1104,14 @@ static int bcm_rx_setup(struct bcm_msg_h
>   		op->rx_ifindex = ifindex;
>   
>   		/* initialize uninitialized (kzalloc) structure */
> -		hrtimer_init(&op->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +		hrtimer_init(&op->timer, CLOCK_MONOTONIC_SOFT,
> +			     HRTIMER_MODE_REL);
>   		op->timer.function = bcm_rx_timeout_handler;
>   
> -		/* initialize tasklet for rx timeout notification */
> -		tasklet_init(&op->tsklet, bcm_rx_timeout_tsklet,
> -			     (unsigned long) op);
> -
> -		hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +		hrtimer_init(&op->thrtimer, CLOCK_MONOTONIC_SOFT,
> +			     HRTIMER_MODE_REL);
>   		op->thrtimer.function = bcm_rx_thr_handler;
>   
> -		/* initialize tasklet for rx throttle handling */
> -		tasklet_init(&op->thrtsklet, bcm_rx_thr_tsklet,
> -			     (unsigned long) op);
> -
>   		/* add this bcm_op to the list of the rx_ops */
>   		list_add(&op->list, &bo->rx_ops);
>   
> @@ -1209,7 +1157,7 @@ static int bcm_rx_setup(struct bcm_msg_h
>   			 */
>   			op->kt_lastmsg = 0;
>   			hrtimer_cancel(&op->thrtimer);
> -			bcm_rx_thr_flush(op, 1);
> +			bcm_rx_thr_flush(op);
>   		}
>   
>   		if ((op->flags & STARTTIMER) && op->kt_ival1)
> 
> 

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