[PATCH v6 0/3] mac802111: channel context reservation

[PATCH v6 0/3] mac802111: channel context reservation

[Luciano Coelho]

Hi,

In v6:

   * return ret in ieee80211_chanctx_is_reserved();
   * check if sdata is running in ieee80211_chanctx_is_reserved();
   * keep check for IEEE80211_CHANCTX_EXCLUSIVE in
     ieee80211_find_channel();
   * use break instead of goto out in ieee80211_chanctx_is_reserved();

In v5:

   * fix checkpatch warnings;

In v4:

   * add chanctx mode parameter to ieee80211_vif_reserve_chanctx();
   * compare the vif's previous BSS width with the reserved new width
     instead of comparing it to the chanctx's combined width;
   * remove IEEE80211_CHANCTX_RESERVED and the reserved_mode element;
   * increase refcount also for "in-place" changes;
   * stop queues also before doing an "in-place" change;
   * refactor ieee80211_use_reserved_chanctx() a bit to fit "in-place"
     better;

In v3:

   * promoted to PATCH ;)
   * applied comments by Michał (see inlined in the patches);
   * removed the "add usage of CS channel reservation for STA" patch,
     since it's independent and is not ready;

This series is based on top of mac80211-next/master, without including
my combination check changes.  When the combination check patchset
gets applied, I can either send the "merge" of the two features as a
separate patchset or I can modify this patchset accordingly (though I
prefer the former, so I can do things in small steps ;).

--
Cheers,
Luca.

Luciano Coelho (3):
  mac80211: split ieee80211_vif_change_channel in two
  mac80211: implement chanctx reservation
  mac80211: allow reservation of a running chanctx

 include/net/mac80211.h     |   7 ++
 net/mac80211/chan.c        | 216 ++++++++++++++++++++++++++++++++++++++++-----
 net/mac80211/ieee80211_i.h |  14 +++
 3 files changed, 217 insertions(+), 20 deletions(-)

-- 
1.9.0

[PATCH v6 1/3] mac80211: split ieee80211_vif_change_channel in two

[Luciano Coelho]

ieee80211_vif_change_channel() locks chanctx_mtx.  When implementing
channel reservation for CS, we will need to call the function to
change channel when the lock is already held, so split the part that
requires the lock out and leave the locking in the original function.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
---
 net/mac80211/chan.c | 58 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 25 deletions(-)

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 42c6592..a27c6ec 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -547,39 +547,20 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
 	return ret;
 }
 
-int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
-				 u32 *changed)
+static int __ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
+					  struct ieee80211_chanctx *ctx,
+					  u32 *changed)
 {
 	struct ieee80211_local *local = sdata->local;
-	struct ieee80211_chanctx_conf *conf;
-	struct ieee80211_chanctx *ctx;
 	const struct cfg80211_chan_def *chandef = &sdata->csa_chandef;
-	int ret;
 	u32 chanctx_changed = 0;
 
-	lockdep_assert_held(&local->mtx);
-
-	/* should never be called if not performing a channel switch. */
-	if (WARN_ON(!sdata->vif.csa_active))
-		return -EINVAL;
-
 	if (!cfg80211_chandef_usable(sdata->local->hw.wiphy, chandef,
 				     IEEE80211_CHAN_DISABLED))
 		return -EINVAL;
 
-	mutex_lock(&local->chanctx_mtx);
-	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
-					 lockdep_is_held(&local->chanctx_mtx));
-	if (!conf) {
-		ret = -EINVAL;
-		goto out;
-	}
-
-	ctx = container_of(conf, struct ieee80211_chanctx, conf);
-	if (ctx->refcount != 1) {
-		ret = -EINVAL;
-		goto out;
-	}
+	if (ctx->refcount != 1)
+		return -EINVAL;
 
 	if (sdata->vif.bss_conf.chandef.width != chandef->width) {
 		chanctx_changed = IEEE80211_CHANCTX_CHANGE_WIDTH;
@@ -597,7 +578,34 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
 	ieee80211_recalc_radar_chanctx(local, ctx);
 	ieee80211_recalc_chanctx_min_def(local, ctx);
 
-	ret = 0;
+	return 0;
+}
+
+int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
+				 u32 *changed)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *conf;
+	struct ieee80211_chanctx *ctx;
+	int ret;
+
+	lockdep_assert_held(&local->mtx);
+
+	/* should never be called if not performing a channel switch. */
+	if (WARN_ON(!sdata->vif.csa_active))
+		return -EINVAL;
+
+	mutex_lock(&local->chanctx_mtx);
+	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+					 lockdep_is_held(&local->chanctx_mtx));
+	if (!conf) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+	ret = __ieee80211_vif_change_channel(sdata, ctx, changed);
  out:
 	mutex_unlock(&local->chanctx_mtx);
 	return ret;
-- 
1.9.0

[PATCH v6 2/3] mac80211: implement chanctx reservation

[Luciano Coelho]

In order to support channel switch with multiple vifs and multiple
contexts, we implement a concept of channel context reservation.  This
allows us to reserve a channel context to be used later.

The reservation functionality is not tied directly to channel switch
and may be used in other situations (eg. reserving a channel context
during IBSS join).

We first check if an existing compatible context exists and if it
does, we reserve it.  If there is no compatible context we create a
new one and reserve it.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
---
In RFC v2:

   * reformulated the patch to make channel reservation generic and
     not only for channel switch, as we may find other uses for it in
     the future;
   * added ieee80211_vif_unreserve_chanctx();
   * removed reservation of the current chanctx from this patch;
   * added a stop_queue_reason for chanctx reservation;
   * added a few TODOs according to Michal's comments to be handled in
     future patch series;
   * set sdata->csa_chandef to the received chandef in all cases (it
     was only happening in the alone-in-the-vif case;

In v3:

   * removed stray empty line;
   * reworded the commit message;
   * added reserved_chandef;
   * added comment about reserved_chanctx and reserved_chandef protection;
   * wake the queues if ieee80211_assign_vif_chanctx() fails;

In v4:

   * add chanctx mode parameter to ieee80211_vif_reserve_chanctx();
   * compare the vif's previous BSS width with the reserved new width
     instead of comparing it to the chanctx's combined width;

In v5:

   * removed a comment that was being removed, mistakenly, on the next
     patch;
---
 net/mac80211/chan.c        | 125 +++++++++++++++++++++++++++++++++++++++++++++
 net/mac80211/ieee80211_i.h |  14 +++++
 2 files changed, 139 insertions(+)

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index a27c6ec..2acf973 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -419,6 +419,9 @@ static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
 
 	ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
+	if (sdata->reserved_chanctx)
+		ieee80211_vif_unreserve_chanctx(sdata);
+
 	ieee80211_unassign_vif_chanctx(sdata, ctx);
 	if (ctx->refcount == 0)
 		ieee80211_free_chanctx(local, ctx);
@@ -611,6 +614,128 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
 	return ret;
 }
 
+int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata)
+{
+	lockdep_assert_held(&sdata->local->chanctx_mtx);
+
+	if (WARN_ON(!sdata->reserved_chanctx))
+		return -EINVAL;
+
+	if (--sdata->reserved_chanctx->refcount == 0)
+		ieee80211_free_chanctx(sdata->local, sdata->reserved_chanctx);
+
+	sdata->reserved_chanctx = NULL;
+
+	return 0;
+}
+
+int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
+				  const struct cfg80211_chan_def *chandef,
+				  enum ieee80211_chanctx_mode mode)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx_conf *conf;
+	struct ieee80211_chanctx *new_ctx, *curr_ctx;
+	int ret = 0;
+
+	mutex_lock(&local->chanctx_mtx);
+
+	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+					 lockdep_is_held(&local->chanctx_mtx));
+	if (!conf) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	curr_ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+	/* try to find another context with the chandef we want */
+	new_ctx = ieee80211_find_chanctx(local, chandef, mode);
+	if (!new_ctx) {
+		/* create a new context */
+		new_ctx = ieee80211_new_chanctx(local, chandef, mode);
+		if (IS_ERR(new_ctx)) {
+			ret = PTR_ERR(new_ctx);
+			goto out;
+		}
+	}
+
+	sdata->reserved_chanctx = new_ctx;
+	new_ctx->refcount++;
+	sdata->reserved_chandef = *chandef;
+out:
+	mutex_unlock(&local->chanctx_mtx);
+	return ret;
+}
+
+int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
+				       u32 *changed)
+{
+	struct ieee80211_local *local = sdata->local;
+	struct ieee80211_chanctx *ctx;
+	struct ieee80211_chanctx *old_ctx;
+	struct ieee80211_chanctx_conf *conf;
+	int ret, local_changed = *changed;
+
+	/* TODO: need to recheck if the chandef is usable etc.? */
+
+	lockdep_assert_held(&local->mtx);
+
+	mutex_lock(&local->chanctx_mtx);
+
+	ctx = sdata->reserved_chanctx;
+	if (WARN_ON(!ctx)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+					 lockdep_is_held(&local->chanctx_mtx));
+	if (!conf) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	old_ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+	ieee80211_stop_queues_by_reason(&local->hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_CHANCTX);
+
+	ieee80211_unassign_vif_chanctx(sdata, old_ctx);
+	if (old_ctx->refcount == 0)
+		ieee80211_free_chanctx(local, old_ctx);
+
+	if (sdata->vif.bss_conf.chandef.width != sdata->reserved_chandef.width)
+		local_changed |= BSS_CHANGED_BANDWIDTH;
+
+	sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
+
+	/* unref our reservation before assigning */
+	ctx->refcount--;
+	sdata->reserved_chanctx = NULL;
+	ret = ieee80211_assign_vif_chanctx(sdata, ctx);
+	if (ret) {
+		/* if assign fails refcount stays the same */
+		if (ctx->refcount == 0)
+			ieee80211_free_chanctx(local, ctx);
+		goto out_wake;
+	}
+
+	*changed = local_changed;
+
+	ieee80211_recalc_chanctx_chantype(local, ctx);
+	ieee80211_recalc_smps_chanctx(local, ctx);
+	ieee80211_recalc_radar_chanctx(local, ctx);
+out_wake:
+	ieee80211_wake_queues_by_reason(&sdata->local->hw,
+					IEEE80211_MAX_QUEUE_MAP,
+					IEEE80211_QUEUE_STOP_REASON_CHANCTX);
+out:
+	mutex_unlock(&local->chanctx_mtx);
+	return ret;
+}
+
 int ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
 				   const struct cfg80211_chan_def *chandef,
 				   u32 *changed)
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8603dfb..ae8acc2 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -756,6 +756,10 @@ struct ieee80211_sub_if_data {
 	bool csa_radar_required;
 	struct cfg80211_chan_def csa_chandef;
 
+	/* context reservation -- protected with chanctx_mtx */
+	struct ieee80211_chanctx *reserved_chanctx;
+	struct cfg80211_chan_def reserved_chandef;
+
 	/* used to reconfigure hardware SM PS */
 	struct work_struct recalc_smps;
 
@@ -899,6 +903,7 @@ enum queue_stop_reason {
 	IEEE80211_QUEUE_STOP_REASON_SKB_ADD,
 	IEEE80211_QUEUE_STOP_REASON_OFFCHANNEL,
 	IEEE80211_QUEUE_STOP_REASON_FLUSH,
+	IEEE80211_QUEUE_STOP_REASON_CHANCTX,
 };
 
 #ifdef CONFIG_MAC80211_LEDS
@@ -1776,6 +1781,15 @@ ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
 			  const struct cfg80211_chan_def *chandef,
 			  enum ieee80211_chanctx_mode mode);
 int __must_check
+ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
+			      const struct cfg80211_chan_def *chandef,
+			      enum ieee80211_chanctx_mode mode);
+int __must_check
+ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
+				   u32 *changed);
+int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata);
+
+int __must_check
 ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
 			       const struct cfg80211_chan_def *chandef,
 			       u32 *changed);
-- 
1.9.0

Re: [PATCH v6 2/3] mac80211: implement chanctx reservation

[Eliad Peller]

hi Luca,

On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
> In order to support channel switch with multiple vifs and multiple
> contexts, we implement a concept of channel context reservation.  This
> allows us to reserve a channel context to be used later.
>
> The reservation functionality is not tied directly to channel switch
> and may be used in other situations (eg. reserving a channel context
> during IBSS join).
>
> We first check if an existing compatible context exists and if it
> does, we reserve it.  If there is no compatible context we create a
> new one and reserve it.
>
> Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
> ---
[...]

> +int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
> +                                      u32 *changed)
> +{
[...]
> +
> +       *changed = local_changed;
> +
> +       ieee80211_recalc_chanctx_chantype(local, ctx);
> +       ieee80211_recalc_smps_chanctx(local, ctx);
> +       ieee80211_recalc_radar_chanctx(local, ctx);

any reason for not calling ieee80211_recalc_chanctx_min_def() as well?

Eliad.

Re: [PATCH v6 2/3] mac80211: implement chanctx reservation

[Luciano Coelho]

On Sun, 2014-03-09 at 17:08 +0200, Eliad Peller wrote:
> hi Luca,
> 
> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
> > In order to support channel switch with multiple vifs and multiple
> > contexts, we implement a concept of channel context reservation.  This
> > allows us to reserve a channel context to be used later.
> >
> > The reservation functionality is not tied directly to channel switch
> > and may be used in other situations (eg. reserving a channel context
> > during IBSS join).
> >
> > We first check if an existing compatible context exists and if it
> > does, we reserve it.  If there is no compatible context we create a
> > new one and reserve it.
> >
> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
> > ---
> [...]
> 
> > +int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
> > +                                      u32 *changed)
> > +{
> [...]
> > +
> > +       *changed = local_changed;
> > +
> > +       ieee80211_recalc_chanctx_chantype(local, ctx);
> > +       ieee80211_recalc_smps_chanctx(local, ctx);
> > +       ieee80211_recalc_radar_chanctx(local, ctx);
> 
> any reason for not calling ieee80211_recalc_chanctx_min_def() as well?

No, it's just missing. :( I'll add it.

--
Luca.

[PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Luciano Coelho]

With single-channel drivers, we need to be able to change a running
chanctx if we want to use chanctx reservation.  Not all drivers may be
able to do this, so add a flag that indicates support for it.

Changing a running chanctx can also be used as an optimization in
multi-channel drivers when the context needs to be reserved for future
usage.

Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
reserved so nobody else can use it (since we know it's going to
change).  In the future, we may allow several vifs to use the same
reservation as long as they plan to use the chanctx on the same
future channel.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
---
In v3:

   * reworded the TODO, slightly;

In v4:

   * remove IEEE80211_CHANCTX_RESERVED and the reserved_mode element;
   * increase refcount also for "in-place" changes;
   * stop queues also before doing an "in-place" change;
   * refactor ieee80211_use_reserved_chanctx() a bit to fit "in-place"
     better;

In v5:

   * fix checkpatch warnings;

In v6:

   * return ret in ieee80211_chanctx_is_reserved();
   * check if sdata is running in ieee80211_chanctx_is_reserved();
   * keep check for IEEE80211_CHANCTX_EXCLUSIVE in
     ieee80211_find_channel();
   * use break instead of goto out in ieee80211_chanctx_is_reserved();
---
 include/net/mac80211.h |  7 ++++
 net/mac80211/chan.c    | 97 ++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 77 insertions(+), 27 deletions(-)

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 86faa41..b35c608 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1553,6 +1553,12 @@ struct ieee80211_tx_control {
  *	for a single active channel while using channel contexts. When support
  *	is not enabled the default action is to disconnect when getting the
  *	CSA frame.
+ *
+ * @IEEE80211_HW_CHANGE_RUNNING_CHANCTX: The hardware can change a
+ *	channel context on-the-fly.  This is needed for channel switch
+ *	on single-channel hardware.  It can also be used as an
+ *	optimization in certain channel switch cases with
+ *	multi-channel.
  */
 enum ieee80211_hw_flags {
 	IEEE80211_HW_HAS_RATE_CONTROL			= 1<<0,
@@ -1584,6 +1590,7 @@ enum ieee80211_hw_flags {
 	IEEE80211_HW_TIMING_BEACON_ONLY			= 1<<26,
 	IEEE80211_HW_SUPPORTS_HT_CCK_RATES		= 1<<27,
 	IEEE80211_HW_CHANCTX_STA_CSA			= 1<<28,
+	IEEE80211_HW_CHANGE_RUNNING_CHANCTX		= 1<<29,
 };
 
 /**
diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 2acf973..a6fdc14 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -162,6 +162,27 @@ static void ieee80211_change_chanctx(struct ieee80211_local *local,
 	}
 }
 
+static bool ieee80211_chanctx_is_reserved(struct ieee80211_local *local,
+				     struct ieee80211_chanctx *ctx)
+{
+	struct ieee80211_sub_if_data *sdata;
+	bool ret = false;
+
+	lockdep_assert_held(&local->chanctx_mtx);
+	rcu_read_lock();
+	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
+		if (!ieee80211_sdata_running(sdata))
+			continue;
+		if (sdata->reserved_chanctx == ctx) {
+			ret = true;
+			break;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret;
+}
+
 static struct ieee80211_chanctx *
 ieee80211_find_chanctx(struct ieee80211_local *local,
 		       const struct cfg80211_chan_def *chandef,
@@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
 	list_for_each_entry(ctx, &local->chanctx_list, list) {
 		const struct cfg80211_chan_def *compat;
 
-		if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
+		/* We don't support chanctx reservation for multiple
+		 * vifs yet, so don't allow reserved chanctxs to be
+		 * reused.
+		 */
+		if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
+		    ieee80211_chanctx_is_reserved(local, ctx))
 			continue;
 
 		compat = cfg80211_chandef_compatible(&ctx->conf.def, chandef);
@@ -652,11 +678,20 @@ int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
 	/* try to find another context with the chandef we want */
 	new_ctx = ieee80211_find_chanctx(local, chandef, mode);
 	if (!new_ctx) {
-		/* create a new context */
-		new_ctx = ieee80211_new_chanctx(local, chandef, mode);
-		if (IS_ERR(new_ctx)) {
-			ret = PTR_ERR(new_ctx);
-			goto out;
+		if (curr_ctx->refcount == 1 &&
+		    (local->hw.flags & IEEE80211_HW_CHANGE_RUNNING_CHANCTX)) {
+			/* if we're the only users of the chanctx and
+			 * the driver supports changing a running
+			 * context, reserve our current context
+			 */
+			new_ctx = curr_ctx;
+		} else {
+			/* create a new context and reserve it */
+			new_ctx = ieee80211_new_chanctx(local, chandef, mode);
+			if (IS_ERR(new_ctx)) {
+				ret = PTR_ERR(new_ctx);
+				goto out;
+			}
 		}
 	}
 
@@ -701,37 +736,45 @@ int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
 	ieee80211_stop_queues_by_reason(&local->hw,
 					IEEE80211_MAX_QUEUE_MAP,
 					IEEE80211_QUEUE_STOP_REASON_CHANCTX);
+	/* unref our reservation */
+	ctx->refcount--;
+	sdata->reserved_chanctx = NULL;
 
-	ieee80211_unassign_vif_chanctx(sdata, old_ctx);
-	if (old_ctx->refcount == 0)
-		ieee80211_free_chanctx(local, old_ctx);
+	if (old_ctx == ctx) {
+		/* This is our own context, just change it */
+		ret = __ieee80211_vif_change_channel(sdata, old_ctx,
+						     &local_changed);
+		if (ret)
+			goto out;
+	} else {
+		ieee80211_unassign_vif_chanctx(sdata, old_ctx);
+		if (old_ctx->refcount == 0)
+			ieee80211_free_chanctx(local, old_ctx);
 
-	if (sdata->vif.bss_conf.chandef.width != sdata->reserved_chandef.width)
-		local_changed |= BSS_CHANGED_BANDWIDTH;
+		if (sdata->vif.bss_conf.chandef.width !=
+		    sdata->reserved_chandef.width)
+			local_changed |= BSS_CHANGED_BANDWIDTH;
 
-	sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
+		sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
 
-	/* unref our reservation before assigning */
-	ctx->refcount--;
-	sdata->reserved_chanctx = NULL;
-	ret = ieee80211_assign_vif_chanctx(sdata, ctx);
-	if (ret) {
-		/* if assign fails refcount stays the same */
-		if (ctx->refcount == 0)
-			ieee80211_free_chanctx(local, ctx);
-		goto out_wake;
+		ret = ieee80211_assign_vif_chanctx(sdata, ctx);
+		if (ret) {
+			/* if assign fails refcount stays the same */
+			if (ctx->refcount == 0)
+				ieee80211_free_chanctx(local, ctx);
+			goto out;
+		}
+
+		ieee80211_recalc_chanctx_chantype(local, ctx);
+		ieee80211_recalc_smps_chanctx(local, ctx);
+		ieee80211_recalc_radar_chanctx(local, ctx);
 	}
 
 	*changed = local_changed;
-
-	ieee80211_recalc_chanctx_chantype(local, ctx);
-	ieee80211_recalc_smps_chanctx(local, ctx);
-	ieee80211_recalc_radar_chanctx(local, ctx);
-out_wake:
+out:
 	ieee80211_wake_queues_by_reason(&sdata->local->hw,
 					IEEE80211_MAX_QUEUE_MAP,
 					IEEE80211_QUEUE_STOP_REASON_CHANCTX);
-out:
 	mutex_unlock(&local->chanctx_mtx);
 	return ret;
 }
-- 
1.9.0

Re: [PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Eliad Peller]

On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
> With single-channel drivers, we need to be able to change a running
> chanctx if we want to use chanctx reservation.  Not all drivers may be
> able to do this, so add a flag that indicates support for it.
>
> Changing a running chanctx can also be used as an optimization in
> multi-channel drivers when the context needs to be reserved for future
> usage.
>
> Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
> reserved so nobody else can use it (since we know it's going to
> change).  In the future, we may allow several vifs to use the same
> reservation as long as they plan to use the chanctx on the same
> future channel.
>
> Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
> ---
[...]

> @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
>         list_for_each_entry(ctx, &local->chanctx_list, list) {
>                 const struct cfg80211_chan_def *compat;
>
> -               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
> +               /* We don't support chanctx reservation for multiple
> +                * vifs yet, so don't allow reserved chanctxs to be
> +                * reused.
> +                */
> +               if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
> +                   ieee80211_chanctx_is_reserved(local, ctx))
>                         continue;
>
i'm not sure that's correct.
you might want to find a chanctx in order to use it, not only for
reservation. any reason to reject it in this case?

Eliad.

Re: [PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Luciano Coelho]

On Sun, 2014-03-09 at 17:13 +0200, Eliad Peller wrote:
> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
> > With single-channel drivers, we need to be able to change a running
> > chanctx if we want to use chanctx reservation.  Not all drivers may be
> > able to do this, so add a flag that indicates support for it.
> >
> > Changing a running chanctx can also be used as an optimization in
> > multi-channel drivers when the context needs to be reserved for future
> > usage.
> >
> > Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
> > reserved so nobody else can use it (since we know it's going to
> > change).  In the future, we may allow several vifs to use the same
> > reservation as long as they plan to use the chanctx on the same
> > future channel.
> >
> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
> > ---
> [...]
> 
> > @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
> >         list_for_each_entry(ctx, &local->chanctx_list, list) {
> >                 const struct cfg80211_chan_def *compat;
> >
> > -               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
> > +               /* We don't support chanctx reservation for multiple
> > +                * vifs yet, so don't allow reserved chanctxs to be
> > +                * reused.
> > +                */
> > +               if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
> > +                   ieee80211_chanctx_is_reserved(local, ctx))
> >                         continue;
> >
> i'm not sure that's correct.
> you might want to find a chanctx in order to use it, not only for
> reservation. any reason to reject it in this case?

At the moment we don't support multi-vifs switching at the same time, so
we don't allow anyone else to use a chanctx while it's reserved.

--
Luca.

Re: [PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Eliad Peller]

On Mon, Mar 10, 2014 at 9:37 AM, Luciano Coelho
<luciano.coelho@intel.com> wrote:
> On Sun, 2014-03-09 at 17:13 +0200, Eliad Peller wrote:
>> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
>> > With single-channel drivers, we need to be able to change a running
>> > chanctx if we want to use chanctx reservation.  Not all drivers may be
>> > able to do this, so add a flag that indicates support for it.
>> >
>> > Changing a running chanctx can also be used as an optimization in
>> > multi-channel drivers when the context needs to be reserved for future
>> > usage.
>> >
>> > Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
>> > reserved so nobody else can use it (since we know it's going to
>> > change).  In the future, we may allow several vifs to use the same
>> > reservation as long as they plan to use the chanctx on the same
>> > future channel.
>> >
>> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
>> > ---
>> [...]
>>
>> > @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
>> >         list_for_each_entry(ctx, &local->chanctx_list, list) {
>> >                 const struct cfg80211_chan_def *compat;
>> >
>> > -               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
>> > +               /* We don't support chanctx reservation for multiple
>> > +                * vifs yet, so don't allow reserved chanctxs to be
>> > +                * reused.
>> > +                */
>> > +               if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
>> > +                   ieee80211_chanctx_is_reserved(local, ctx))
>> >                         continue;
>> >
>> i'm not sure that's correct.
>> you might want to find a chanctx in order to use it, not only for
>> reservation. any reason to reject it in this case?
>
> At the moment we don't support multi-vifs switching at the same time, so
> we don't allow anyone else to use a chanctx while it's reserved.
>
i'm not talking about multi-vifs switching.
consider the following scenario:
sta connected on channel 40
ap beaconing on channel 60

now, you want (for whatever reason) to switch the ap to channel 40.
you'll reserve the sta's chanctx, and increase its refcount (to 2).

now a new sta vif is added, and tries to connect on channel 40.
the check above will skip the existing channel context (because it's
also reserved) although there is no reason it won't be used.

Eliad.

Re: [PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Michal Kazior]

On 10 March 2014 09:32, Eliad Peller <eliad@wizery.com> wrote:
> On Mon, Mar 10, 2014 at 9:37 AM, Luciano Coelho
> <luciano.coelho@intel.com> wrote:
>> On Sun, 2014-03-09 at 17:13 +0200, Eliad Peller wrote:
>>> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
>>> > With single-channel drivers, we need to be able to change a running
>>> > chanctx if we want to use chanctx reservation.  Not all drivers may be
>>> > able to do this, so add a flag that indicates support for it.
>>> >
>>> > Changing a running chanctx can also be used as an optimization in
>>> > multi-channel drivers when the context needs to be reserved for future
>>> > usage.
>>> >
>>> > Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
>>> > reserved so nobody else can use it (since we know it's going to
>>> > change).  In the future, we may allow several vifs to use the same
>>> > reservation as long as they plan to use the chanctx on the same
>>> > future channel.
>>> >
>>> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
>>> > ---
>>> [...]
>>>
>>> > @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
>>> >         list_for_each_entry(ctx, &local->chanctx_list, list) {
>>> >                 const struct cfg80211_chan_def *compat;
>>> >
>>> > -               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
>>> > +               /* We don't support chanctx reservation for multiple
>>> > +                * vifs yet, so don't allow reserved chanctxs to be
>>> > +                * reused.
>>> > +                */
>>> > +               if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
>>> > +                   ieee80211_chanctx_is_reserved(local, ctx))
>>> >                         continue;
>>> >
>>> i'm not sure that's correct.
>>> you might want to find a chanctx in order to use it, not only for
>>> reservation. any reason to reject it in this case?
>>
>> At the moment we don't support multi-vifs switching at the same time, so
>> we don't allow anyone else to use a chanctx while it's reserved.
>>
> i'm not talking about multi-vifs switching.
> consider the following scenario:
> sta connected on channel 40
> ap beaconing on channel 60
>
> now, you want (for whatever reason) to switch the ap to channel 40.
> you'll reserve the sta's chanctx, and increase its refcount (to 2).
>
> now a new sta vif is added, and tries to connect on channel 40.
> the check above will skip the existing channel context (because it's
> also reserved) although there is no reason it won't be used.

Good point. I have this case covered in my multi-vif csa patches. We
could transplant it into Luca's patch?


Michał

Re: [PATCH v6 3/3] mac80211: allow reservation of a running chanctx

[Luca Coelho]

On Mon, 2014-03-10 at 10:03 +0100, Michal Kazior wrote:
> On 10 March 2014 09:32, Eliad Peller <eliad@wizery.com> wrote:
> > On Mon, Mar 10, 2014 at 9:37 AM, Luciano Coelho
> > <luciano.coelho@intel.com> wrote:
> >> On Sun, 2014-03-09 at 17:13 +0200, Eliad Peller wrote:
> >>> On Sun, Mar 9, 2014 at 4:40 PM, Luciano Coelho <luciano.coelho@intel.com> wrote:
> >>> > With single-channel drivers, we need to be able to change a running
> >>> > chanctx if we want to use chanctx reservation.  Not all drivers may be
> >>> > able to do this, so add a flag that indicates support for it.
> >>> >
> >>> > Changing a running chanctx can also be used as an optimization in
> >>> > multi-channel drivers when the context needs to be reserved for future
> >>> > usage.
> >>> >
> >>> > Introduce IEEE80211_CHANCTX_RESERVED chanctx mode to mark a channel as
> >>> > reserved so nobody else can use it (since we know it's going to
> >>> > change).  In the future, we may allow several vifs to use the same
> >>> > reservation as long as they plan to use the chanctx on the same
> >>> > future channel.
> >>> >
> >>> > Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
> >>> > ---
> >>> [...]
> >>>
> >>> > @@ -177,7 +198,12 @@ ieee80211_find_chanctx(struct ieee80211_local *local,
> >>> >         list_for_each_entry(ctx, &local->chanctx_list, list) {
> >>> >                 const struct cfg80211_chan_def *compat;
> >>> >
> >>> > -               if (ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE)
> >>> > +               /* We don't support chanctx reservation for multiple
> >>> > +                * vifs yet, so don't allow reserved chanctxs to be
> >>> > +                * reused.
> >>> > +                */
> >>> > +               if ((ctx->mode == IEEE80211_CHANCTX_EXCLUSIVE) ||
> >>> > +                   ieee80211_chanctx_is_reserved(local, ctx))
> >>> >                         continue;
> >>> >
> >>> i'm not sure that's correct.
> >>> you might want to find a chanctx in order to use it, not only for
> >>> reservation. any reason to reject it in this case?
> >>
> >> At the moment we don't support multi-vifs switching at the same time, so
> >> we don't allow anyone else to use a chanctx while it's reserved.
> >>
> > i'm not talking about multi-vifs switching.
> > consider the following scenario:
> > sta connected on channel 40
> > ap beaconing on channel 60
> >
> > now, you want (for whatever reason) to switch the ap to channel 40.
> > you'll reserve the sta's chanctx, and increase its refcount (to 2).
> >
> > now a new sta vif is added, and tries to connect on channel 40.
> > the check above will skip the existing channel context (because it's
> > also reserved) although there is no reason it won't be used.
> 
> Good point. I have this case covered in my multi-vif csa patches. We
> could transplant it into Luca's patch?

Yes, it's a good point.  What would happen with this patch is that the
new STA will get a new chanctx, so in theory it would still work (though
wasting resources. as it could be).

If your fix is simple, we could transplant it here.  But if it's more
complex, I think we could have it as a new patch on top of my series.
Nobody is using channel reservation yet, so I don't think that would be
a big problem.

--
Luca.