DPDK patches and discussions
 help / color / mirror / Atom feed
From: Neil Horman <nhorman@tuxdriver.com>
To: "Wodkowski, PawelX" <pawelx.wodkowski@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"Jastrzebski, MichalX K" <michalx.k.jastrzebski@intel.com>
Subject: Re: [dpdk-dev] [PATCH 2/2] bond: add mode 4 support
Date: Thu, 18 Sep 2014 12:02:34 -0400
Message-ID: <20140918160234.GJ20389@hmsreliant.think-freely.org> (raw)
In-Reply-To: <F6F2A6264E145F47A18AB6DF8E87425D12B24CC2@IRSMSX102.ger.corp.intel.com>

On Thu, Sep 18, 2014 at 08:07:31AM +0000, Wodkowski, PawelX wrote:
> > > +int
> > > +bond_mode_8023ad_deactivate_slave(struct rte_eth_dev *bond_dev,
> > > +		uint8_t slave_pos)
> > > +{
> > > +	struct bond_dev_private *internals = bond_dev->data->dev_private;
> > > +	struct mode8023ad_data *data = &internals->mode4;
> > > +	struct port *port;
> > > +	uint8_t i;
> > > +
> > > +	bond_mode_8023ad_stop(bond_dev);
> > > +
> > > +	/* Exclude slave from transmit policy. If this slave is an aggregator
> > > +	 * make all aggregated slaves unselected to force sellection logic
> > > +	 * to select suitable aggregator for this port	 */
> > > +	for (i = 0; i < internals->active_slave_count; i++) {
> > > +		port = &data->port_list[slave_pos];
> > > +		if (port->used_agregator_idx == slave_pos) {
> > > +			port->selected = UNSELECTED;
> > > +			port->actor_state &= ~(STATE_SYNCHRONIZATION |
> > STATE_DISTRIBUTING |
> > > +				STATE_COLLECTING);
> > > +
> > > +			/* Use default aggregator */
> > > +			port->used_agregator_idx = i;
> > > +		}
> > > +	}
> > > +
> > > +	port = &data->port_list[slave_pos];
> > > +	timer_cancel(&port->current_while_timer);
> > > +	timer_cancel(&port->periodic_timer);
> > > +	timer_cancel(&port->wait_while_timer);
> > > +	timer_cancel(&port->tx_machine_timer);
> > > +
> > These all seem rather racy.  Alarm callbacks are executed with the alarm list
> > locks not held.  So there is every possibility that you could execute these (or
> > any timer_cancel calls in this PMD in parallel with the internal state machine
> > timer callback, and leave either with a corrupted timer list (resulting from a
> > double free between here, and the actual callback site),
> 
> I don't think so. Yes, callbacks are executed with  alarm list locks not held, but 
> this is not the issue because access to list itself is guarded by lock and 
> ap->executing variable. So list will not be trashed. Check source of 
> eal_alarm_callback(), rte_eal_alarm_set() and rte_eal_alarm_cancel().
> 
Yes, you're right, the list is probably safe wht the executing bit.

> > or a timer that is
> > actually still pending when a slave is removed.
> > 
> This is not the issue also, but problem might be similar. I assumed that alarms
> are atomic but when I looked at rte alarms closer I saw a race condition
> between and rte_eal_alarm_cancel() from  bond_mode_8023ad_stop()
> and rte_eal_alarm_set() from state machines callback. This need to be 
> reworked in some way.

Yes, this is what I was referring to:

CPU0				CPU1
rte_eal_alarm_callback		bond_8023ad_deactivate_slave
-bond_8023_ad_periodic_cb	timer_cancel
timer_set

If those timer functions operate on the same timer, the result is that you can
leave the stop/deactivate slave paths with a timer function for that slave still
pending. The bonding mode needs some internal state to serialize those
operations and determine if the timer should be reactivated.

Neil

  reply	other threads:[~2014-09-18 15:56 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-17 14:21 [dpdk-dev] [PATCH 0/2] " Pawel Wodkowski
2014-09-17 14:21 ` [dpdk-dev] [PATCH 1/2] bond: extract common code to separate functions Pawel Wodkowski
2014-09-17 14:51   ` Neil Horman
2014-09-17 14:21 ` [dpdk-dev] [PATCH 2/2] bond: add mode 4 support Pawel Wodkowski
2014-09-17 15:13   ` Neil Horman
2014-09-18  8:07     ` Wodkowski, PawelX
2014-09-18 16:02       ` Neil Horman [this message]
2014-09-19 12:47         ` Wodkowski, PawelX
2014-09-19 17:29           ` Neil Horman
2014-09-22  6:26             ` Wodkowski, PawelX
2014-09-22 10:24               ` Neil Horman
     [not found]                 ` <60ABE07DBB3A454EB7FAD707B4BB158213896977@IRSMSX109.ger.corp.intel.com>
2014-09-22 13:15                   ` Neil Horman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20140918160234.GJ20389@hmsreliant.think-freely.org \
    --to=nhorman@tuxdriver.com \
    --cc=dev@dpdk.org \
    --cc=michalx.k.jastrzebski@intel.com \
    --cc=pawelx.wodkowski@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git