linux/3.2: R.I.P.

SVN-Revision: 31905

1 files changed, 0 insertions, 188 deletions

diff --git a/target/linux/generic/patches-3.2/130-pppoatm-queue-depth.patch b/target/linux/generic/patches-3.2/130-pppoatm-queue-depth.patch
deleted file mode 100644
index 247a312290..0000000000
--- a/target/linux/generic/patches-3.2/130-pppoatm-queue-depth.patch
+++ /dev/null
@@ -1,188 +0,0 @@
-From 9d02daf754238adac48fa075ee79e7edd3d79ed3 Mon Sep 17 00:00:00 2001
-From: David Woodhouse <dwmw2@infradead.org>
-Date: Sun, 8 Apr 2012 09:55:43 +0000
-Subject: [PATCH] pppoatm: Fix excessive queue bloat
-
-We discovered that PPPoATM has an excessively deep transmit queue. A
-queue the size of the default socket send buffer (wmem_default) is
-maintained between the PPP generic core and the ATM device.
-
-Fix it to queue a maximum of *two* packets. The one the ATM device is
-currently working on, and one more for the ATM driver to process
-immediately in its TX done interrupt handler. The PPP core is designed
-to feed packets to the channel with minimal latency, so that really
-ought to be enough to keep the ATM device busy.
-
-While we're at it, fix the fact that we were triggering the wakeup
-tasklet on *every* pppoatm_pop() call. The comment saying "this is
-inefficient, but doing it right is too hard" turns out to be overly
-pessimistic... I think :)
-
-On machines like the Traverse Geos, with a slow Geode CPU and two
-high-speed ADSL2+ interfaces, there were reports of extremely high CPU
-usage which could partly be attributed to the extra wakeups.
-
-(The wakeup handling could actually be made a whole lot easier if we
- stop checking sk->sk_sndbuf altogether. Given that we now only queue
- *two* packets ever, one wonders what the point is. As it is, you could
- already deadlock the thing by setting the sk_sndbuf to a value lower
- than the MTU of the device, and it'd just block for ever.)
-
-Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
-Signed-off-by: David S. Miller <davem@davemloft.net>
----
- net/atm/pppoatm.c |   95 +++++++++++++++++++++++++++++++++++++++++++++++-----
- 1 files changed, 85 insertions(+), 10 deletions(-)
-
---- a/net/atm/pppoatm.c
-+++ b/net/atm/pppoatm.c
-@@ -62,12 +62,25 @@ struct pppoatm_vcc {
- 	void (*old_pop)(struct atm_vcc *, struct sk_buff *);
- 					/* keep old push/pop for detaching */
- 	enum pppoatm_encaps encaps;
-+	atomic_t inflight;
-+	unsigned long blocked;
- 	int flags;			/* SC_COMP_PROT - compress protocol */
- 	struct ppp_channel chan;	/* interface to generic ppp layer */
- 	struct tasklet_struct wakeup_tasklet;
- };
- 
- /*
-+ * We want to allow two packets in the queue. The one that's currently in
-+ * flight, and *one* queued up ready for the ATM device to send immediately
-+ * from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so
-+ * inflight == -2 represents an empty queue, -1 one packet, and zero means
-+ * there are two packets in the queue.
-+ */
-+#define NONE_INFLIGHT -2
-+
-+#define BLOCKED 0
-+
-+/*
-  * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
-  * ID (0xC021) used in autodetection
-  */
-@@ -102,16 +115,30 @@ static void pppoatm_wakeup_sender(unsign
- static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
- {
- 	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
-+
- 	pvcc->old_pop(atmvcc, skb);
-+	atomic_dec(&pvcc->inflight);
-+
- 	/*
--	 * We don't really always want to do this since it's
--	 * really inefficient - it would be much better if we could
--	 * test if we had actually throttled the generic layer.
--	 * Unfortunately then there would be a nasty SMP race where
--	 * we could clear that flag just as we refuse another packet.
--	 * For now we do the safe thing.
-+	 * We always used to run the wakeup tasklet unconditionally here, for
-+	 * fear of race conditions where we clear the BLOCKED flag just as we
-+	 * refuse another packet in pppoatm_send(). This was quite inefficient.
-+	 *
-+	 * In fact it's OK. The PPP core will only ever call pppoatm_send()
-+	 * while holding the channel->downl lock. And ppp_output_wakeup() as
-+	 * called by the tasklet will *also* grab that lock. So even if another
-+	 * CPU is in pppoatm_send() right now, the tasklet isn't going to race
-+	 * with it. The wakeup *will* happen after the other CPU is safely out
-+	 * of pppoatm_send() again.
-+	 *
-+	 * So if the CPU in pppoatm_send() has already set the BLOCKED bit and
-+	 * it about to return, that's fine. We trigger a wakeup which will
-+	 * happen later. And if the CPU in pppoatm_send() *hasn't* set the
-+	 * BLOCKED bit yet, that's fine too because of the double check in
-+	 * pppoatm_may_send() which is commented there.
- 	 */
--	tasklet_schedule(&pvcc->wakeup_tasklet);
-+	if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
-+		tasklet_schedule(&pvcc->wakeup_tasklet);
- }
- 
- /*
-@@ -184,6 +211,51 @@ error:
- 	ppp_input_error(&pvcc->chan, 0);
- }
- 
-+static inline int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
-+{
-+	/*
-+	 * It's not clear that we need to bother with using atm_may_send()
-+	 * to check we don't exceed sk->sk_sndbuf. If userspace sets a
-+	 * value of sk_sndbuf which is lower than the MTU, we're going to
-+	 * block for ever. But the code always did that before we introduced
-+	 * the packet count limit, so...
-+	 */
-+	if (atm_may_send(pvcc->atmvcc, size) &&
-+	    atomic_inc_not_zero_hint(&pvcc->inflight, NONE_INFLIGHT))
-+		return 1;
-+
-+	/*
-+	 * We use test_and_set_bit() rather than set_bit() here because
-+	 * we need to ensure there's a memory barrier after it. The bit
-+	 * *must* be set before we do the atomic_inc() on pvcc->inflight.
-+	 * There's no smp_mb__after_set_bit(), so it's this or abuse
-+	 * smp_mb__after_clear_bit().
-+	 */
-+	test_and_set_bit(BLOCKED, &pvcc->blocked);
-+
-+	/*
-+	 * We may have raced with pppoatm_pop(). If it ran for the
-+	 * last packet in the queue, *just* before we set the BLOCKED
-+	 * bit, then it might never run again and the channel could
-+	 * remain permanently blocked. Cope with that race by checking
-+	 * *again*. If it did run in that window, we'll have space on
-+	 * the queue now and can return success. It's harmless to leave
-+	 * the BLOCKED flag set, since it's only used as a trigger to
-+	 * run the wakeup tasklet. Another wakeup will never hurt.
-+	 * If pppoatm_pop() is running but hasn't got as far as making
-+	 * space on the queue yet, then it hasn't checked the BLOCKED
-+	 * flag yet either, so we're safe in that case too. It'll issue
-+	 * an "immediate" wakeup... where "immediate" actually involves
-+	 * taking the PPP channel's ->downl lock, which is held by the
-+	 * code path that calls pppoatm_send(), and is thus going to
-+	 * wait for us to finish.
-+	 */
-+	if (atm_may_send(pvcc->atmvcc, size) &&
-+	    atomic_inc_not_zero(&pvcc->inflight))
-+		return 1;
-+
-+	return 0;
-+}
- /*
-  * Called by the ppp_generic.c to send a packet - returns true if packet
-  * was accepted.  If we return false, then it's our job to call
-@@ -207,7 +279,7 @@ static int pppoatm_send(struct ppp_chann
- 			struct sk_buff *n;
- 			n = skb_realloc_headroom(skb, LLC_LEN);
- 			if (n != NULL &&
--			    !atm_may_send(pvcc->atmvcc, n->truesize)) {
-+			    !pppoatm_may_send(pvcc, n->truesize)) {
- 				kfree_skb(n);
- 				goto nospace;
- 			}
-@@ -215,12 +287,12 @@ static int pppoatm_send(struct ppp_chann
- 			skb = n;
- 			if (skb == NULL)
- 				return DROP_PACKET;
--		} else if (!atm_may_send(pvcc->atmvcc, skb->truesize))
-+		} else if (!pppoatm_may_send(pvcc, skb->truesize))
- 			goto nospace;
- 		memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
- 		break;
- 	case e_vc:
--		if (!atm_may_send(pvcc->atmvcc, skb->truesize))
-+		if (!pppoatm_may_send(pvcc, skb->truesize))
- 			goto nospace;
- 		break;
- 	case e_autodetect:
-@@ -285,6 +357,9 @@ static int pppoatm_assign_vcc(struct atm
- 	if (pvcc == NULL)
- 		return -ENOMEM;
- 	pvcc->atmvcc = atmvcc;
-+
-+	/* Maximum is zero, so that we can use atomic_inc_not_zero() */
-+	atomic_set(&pvcc->inflight, NONE_INFLIGHT);
- 	pvcc->old_push = atmvcc->push;
- 	pvcc->old_pop = atmvcc->pop;
- 	pvcc->encaps = (enum pppoatm_encaps) be.encaps;