Subject: Re: [v2,net-next,1/3] net: stmmac: enable multiple buffers

From: Thierry Reding <[email-masked]>
Date: Thu, 23 Mar 2017 19:10:59 +0100

On Thu, Mar 23, 2017 at 05:27:08PM +0000, Joao Pinto wrote:
> Hi Thierry,
> 
> Às 5:17 PM de 3/23/2017, Thierry Reding escreveu:
> > On Fri, Mar 17, 2017 at 04:11:05PM +0000, Joao Pinto wrote:
> >> This patch creates 2 new structures (stmmac_tx_queue and stmmac_rx_queue)
> >> in include/linux/stmmac.h, enabling that each RX and TX queue has its
> >> own buffers and data.
> >>
> >> Signed-off-by: Joao Pinto <[email-masked]>
> >> ---
> >> changes v1->v2:
> >> - just to keep up version
> >>
> >>  drivers/net/ethernet/stmicro/stmmac/chain_mode.c  |   45 +-
> >>  drivers/net/ethernet/stmicro/stmmac/ring_mode.c   |   46 +-
> >>  drivers/net/ethernet/stmicro/stmmac/stmmac.h      |   49 +-
> >>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 1306 ++++++++++++++-------
> >>  4 files changed, 973 insertions(+), 473 deletions(-)
> > 
> > Hi Joao,
> > 
> > This seems to break support on Tegra186 again. I've gone through this
> > patch multiple times and I can't figure out what could be causing it.
> > Any ideas?
> > 
> > What I'm seeing is that the transmit queue 0 times out:
> > 
> > 	[  101.121774] Sending DHCP requests ...
> > 	[  111.841763] NETDEV WATCHDOG: eth0 (dwc-eth-dwmac): transmit queue 0 timed out
> 
> You are using a GMAC or GMAC4 aka QoS?

Yes. It's called EQOS (or EAVB) on Tegra186.

> > and then I also see this:
> > 
> > 	[  112.252024] dwc-eth-dwmac 2490000.ethernet: DMA-API: device driver tries to free DMA memory it has not allocated [device address=0x0000000057ac6e9d] [size=0 bytes]
> 
> Humm... Something in stmmac_free_tx_buffers... I'll need to check.
> 
> > 	[  112.266606] ------------[ cut here ]------------
> > 	[  112.271220] WARNING: CPU: 0 PID: 0 at /home/thierry.reding/src/kernel/linux-tegra.git/lib/dma-debug.c:1106 check_unmap+0x7b0/0x930
> > 	[  112.282934] Modules linked in:
> > 	[  112.285985]
> > 	[  112.287474] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G S      W       4.11.0-rc3-next-20170323-00060-g2eab4557749b-dirty #400
> > 	[  112.298581] Hardware name: NVIDIA Tegra186 P2771-0000 Development Board (DT)
> > 	[  112.305615] task: ffff000008f87b00 task.stack: ffff000008f70000
> > 	[  112.311523] PC is at check_unmap+0x7b0/0x930
> > 	[  112.315785] LR is at check_unmap+0x7b0/0x930
> > 	[  112.320046] pc : [<ffff0000083d75f0>] lr : [<ffff0000083d75f0>] pstate: 60000145
> > 	[  112.327426] sp : ffff8001f5e50c50
> > 	[  112.330733] x29: ffff8001f5e50c50 x28: ffff000008f75180
> > 	[  112.336042] x27: ffff000008f87b00 x26: 0000000000000020
> > 	[  112.341351] x25: 0000000000000140 x24: ffff000008f81000
> > 	[  112.346660] x23: ffff8001ec4b0810 x22: 0000000057ac6e9d
> > 	[  112.351969] x21: 0000000057ac6e9d x20: ffff8001f5e50cb0
> > 	[  112.357277] x19: ffff8001ec4b0810 x18: 0000000000000010
> > 	[  112.362586] x17: 00000000262ea01f x16: 000000000f48bf67
> > 	[  112.367895] x15: 0000000000000006 x14: 5d64396536636137
> > 	[  112.373203] x13: 3530303030303030 x12: 3078303d73736572
> > 	[  112.378511] x11: 6464612065636976 x10: 65645b2064657461
> > 	[  112.383819] x9 : ffff00000852c238 x8 : 00000000000001fb
> > 	[  112.389126] x7 : 0000000000000000 x6 : ffff00000810ad58
> > 	[  112.394434] x5 : 0000000000000000 x4 : 0000000000000000
> > 	[  112.399743] x3 : ffffffffffffffff x2 : ffff000008f99258
> > 	[  112.405050] x1 : ffff000008f87b00 x0 : 0000000000000097
> > 	[  112.410358]
> > 	[  112.411846] ---[ end trace 48028f96a0e990fb ]---
> > 	[  112.416453] Call trace:
> > 	[  112.418895] Exception stack(0xffff8001f5e50a80 to 0xffff8001f5e50bb0)
> > 	[  112.425324] 0a80: ffff8001ec4b0810 0001000000000000 ffff8001f5e50c50 ffff0000083d75f0
> > 	[  112.433139] 0aa0: 00000000000001c0 0000000000000000 0000000000000000 ffff000008d1c0c0
> > 	[  112.440954] 0ac0: ffff8001f5e50c50 ffff8001f5e50c50 ffff8001f5e50c10 00000000ffffffc8
> > 	[  112.448769] 0ae0: ffff8001f5e50b10 ffff00000810c3a8 ffff8001f5e50c50 ffff8001f5e50c50
> > 	[  112.456585] 0b00: ffff8001f5e50c10 00000000ffffffc8 ffff8001f5e50bc0 ffff000008178388
> > 	[  112.464399] 0b20: 0000000000000097 ffff000008f87b00 ffff000008f99258 ffffffffffffffff
> > 	[  112.472215] 0b40: 0000000000000000 0000000000000000 ffff00000810ad58 0000000000000000
> > 	[  112.480030] 0b60: 00000000000001fb ffff00000852c238 65645b2064657461 6464612065636976
> > 	[  112.487845] 0b80: 3078303d73736572 3530303030303030 5d64396536636137 0000000000000006
> > 	[  112.495659] 0ba0: 000000000f48bf67 00000000262ea01f
> > 	[  112.500528] [<ffff0000083d75f0>] check_unmap+0x7b0/0x930
> > 	[  112.505830] [<ffff0000083d77d8>] debug_dma_unmap_page+0x68/0x70
> > 	[  112.511744] [<ffff0000086a9654>] stmmac_free_tx_buffers.isra.1+0x114/0x198
> > 	[  112.518604] [<ffff0000086a9754>] stmmac_tx_err+0x7c/0x160
> > 	[  112.523993] [<ffff0000086a986c>] stmmac_tx_timeout+0x34/0x50
> > 	[  112.529642] [<ffff0000088a1938>] dev_watchdog+0x270/0x2a8
> > 	[  112.535032] [<ffff000008120774>] call_timer_fn+0x64/0xd0
> > 	[  112.540334] [<ffff000008120890>] expire_timers+0xb0/0xc0
> > 	[  112.545636] [<ffff0000081209f8>] run_timer_softirq+0x80/0xc0
> > 	[  112.551284] [<ffff0000080c517c>] __do_softirq+0x10c/0x218
> > 	[  112.556673] [<ffff0000080c55b0>] irq_exit+0xc8/0x118
> > 	[  112.561629] [<ffff00000810cc50>] __handle_domain_irq+0x60/0xb8
> > 	[  112.567450] [<ffff00000808154c>] gic_handle_irq+0x54/0xa8
> > 	[  112.572837] Exception stack(0xffff000008f73dd0 to 0xffff000008f73f00)
> > 	[  112.579264] 3dc0:                                   0000000000000000 0000000000000000
> > 	[  112.587079] 3de0: 0000000000000001 0000000000000000 ffffffffffffea60 ffff000008f73f00
> > 	[  112.594894] 3e00: 00000000000000c0 0000000000000000 0000000000000028 ffff000008f73e40
> > 	[  112.602709] 3e20: 0000000000001130 00000000fa83b2da ffff000008a313a0 0000000000000001
> > 	[  112.610524] 3e40: 0000000000000000 00000019ebd06fc0 000000000f48bf67 00000000262ea01f
> > 	[  112.618338] 3e60: 0000000000000010 ffff000008f2b000 ffff000008f7eb58 ffff000008f7e000
> > 	[  112.626152] 3e80: ffff000008f371a0 0000000000000000 0000000000000000 ffff000008f87b00
> > 	[  112.633967] 3ea0: 00000000eff9cf10 0000000000000000 0000000080e60018 ffff000008f73f00
> > 	[  112.641782] 3ec0: ffff00000808524c ffff000008f73f00 ffff000008085250 0000000000000045
> > 	[  112.649597] 3ee0: ffff000008f73f00 00000000ffff47c0 ffffffffffffffff 7fffffffffffffff
> > 	[  112.657411] [<ffff0000080827f4>] el1_irq+0xb4/0x128
> > 	[  112.662280] [<ffff000008085250>] arch_cpu_idle+0x10/0x18
> > 	[  112.667581] [<ffff0000080fbbdc>] do_idle+0x10c/0x1f0
> > 	[  112.672537] [<ffff0000080fbeb8>] cpu_startup_entry+0x20/0x28
> > 	[  112.678185] [<ffff000008a0aa64>] rest_init+0xbc/0xc8
> > 	[  112.683140] [<ffff000008e60b4c>] start_kernel+0x384/0x398
> > 	[  112.688528] [<ffff000008e601e0>] __primary_switched+0x64/0x6c
> > 
> > And finally this:
> 
> Here it tries to access the descriptors when apparently they don't exist anymore.
> 
> > 
> > 	[  112.843438] x1 : 0000000000000000 x0 : ffff000008061000
> > 	[  112.848743]
> > 	[  112.850229] Process swapper/0 (pid: 0, stack limit = 0xffff000008f70000)
> > 	[  112.856916] Stack: (0xffff8001f5e50d80 to 0xffff000008f74000)
> > 	[  112.862647] Call trace:
> > 	[  112.918392] 0c60: 0000000000000000 ffff0000086b4790 0000000000000080 ffff000008865ed8
> > 	[  112.926206] 0c80: ffff0000083d7038 0000000000210d00 0000000040000000 ffff00000852c238
> > 	[  112.934018] 0ca0: 65645b2064657461 6464612065636976 3078303d73736572 3530303030303030
> > 	[  112.941831] 0cc0: 5d64396536636137 0000000000000006 000000000f48bf67 00000000262ea01f
> > 	[  112.949645] [<ffff0000086b4790>] dwmac4_rd_init_tx_desc+0x0/0x10
> > 	[  112.955638] [<ffff0000086a986c>] stmmac_tx_timeout+0x34/0x50
> > 	[  112.961285] [<ffff0000088a1938>] dev_watchdog+0x270/0x2a8
> > 	[  112.966672] [<ffff000008120774>] call_timer_fn+0x64/0xd0
> > 	[  112.971973] [<ffff000008120890>] expire_timers+0xb0/0xc0
> > 	[  112.977274] [<ffff0000081209f8>] run_timer_softirq+0x80/0xc0
> > 	[  112.982920] [<ffff0000080c517c>] __do_softirq+0x10c/0x218
> > 	[  112.988307] [<ffff0000080c55b0>] irq_exit+0xc8/0x118
> > 
> > The above is with one small change already applied, which seemed like it
> > would be significant, but it didn't have much effect. See below...
> > 
> >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > [...]
> >> @@ -2977,14 +3356,22 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
> >>   */
> >>  static int stmmac_poll(struct napi_struct *napi, int budget)
> >>  {
> >> -	struct stmmac_priv *priv = container_of(napi, struct stmmac_priv, napi);
> >> -	int work_done = 0;
> >> -	u32 chan = STMMAC_CHAN0;
> >> +	struct stmmac_rx_queue *rx_q =
> >> +		container_of(napi, struct stmmac_rx_queue, napi);
> >> +	struct stmmac_priv *priv = rx_q->priv_data;
> >> +	u32 tx_count = priv->dma_cap.number_tx_queues;
> > 
> > I changed this to priv->plat->tx_queues_to_use as used elsewhere to make
> > sure we don't try to clean up non-initialized TX queues. This seems to
> > solve an issue that would occasionally happen after the TX queue timed
> > out, but the fundamental issue is still there.
> 
> Yes, you are correct. It should be priv->plat->tx_queues_to_use instead of "u32
> tx_count = priv->dma_cap.number_tx_queues;"... sorry for that, but in my setup
> is the same value. Could you please make a patch for it?

Yes, I can submit a patch for that.

After some more testing I did get a couple (roughly 2 out of 10)
successful boots (I'm booting over NFS using the EQOS), and given that
this pointed towards something related to uninitialized data, I changed
all occurrences of kmalloc_array() with kcalloc() and that I've gotten
10 successful reboots out of 10.

I still can't pinpoint why this is now necessary since previously the
kmalloc_array() was working just fine. The only thing I can think of is
that we're not properly initializing all fields of the new queue
structures, since that's the only thing that's changed with this commit.

I haven't investigated in detail yet, but from nothing so far has jumped
out at me.

Thierry