From: Eric Dumazet <edumazet@xxxxxxxxxx>
Marek reported a LOCKDEP issue occurring on 32bit host,
that we tracked down to the fact that usbnet could either
run from soft or hard irqs.
This patch adds u64_stats_update_begin_irqsave() and
u64_stats_update_end_irqrestore() helpers to solve this case.
[ 17.768040] ================================
[ 17.772239] WARNING: inconsistent lock state
[ 17.776511] 4.16.0-rc3-next-20180227-00007-g876c53a7493c #453 Not tainted
[ 17.783329] --------------------------------
[ 17.787580] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[ 17.793607] swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[ 17.798751] (&syncp->seq#5){?.-.}, at: [<9b22e5f0>]
asix_rx_fixup_internal+0x188/0x288
[ 17.806790] {IN-HARDIRQ-W} state was registered at:
[ 17.811677] tx_complete+0x100/0x208
[ 17.815319] __usb_hcd_giveback_urb+0x60/0xf0
[ 17.819770] xhci_giveback_urb_in_irq+0xa8/0x240
[ 17.824469] xhci_td_cleanup+0xf4/0x16c
[ 17.828367] xhci_irq+0xe74/0x2240
[ 17.831827] usb_hcd_irq+0x24/0x38
[ 17.835343] __handle_irq_event_percpu+0x98/0x510
[ 17.840111] handle_irq_event_percpu+0x1c/0x58
[ 17.844623] handle_irq_event+0x38/0x5c
[ 17.848519] handle_fasteoi_irq+0xa4/0x138
[ 17.852681] generic_handle_irq+0x18/0x28
[ 17.856760] __handle_domain_irq+0x6c/0xe4
[ 17.860941] gic_handle_irq+0x54/0xa0
[ 17.864666] __irq_svc+0x70/0xb0
[ 17.867964] arch_cpu_idle+0x20/0x3c
[ 17.871578] arch_cpu_idle+0x20/0x3c
[ 17.875190] do_idle+0x144/0x218
[ 17.878468] cpu_startup_entry+0x18/0x1c
[ 17.882454] start_kernel+0x394/0x400
[ 17.886177] irq event stamp: 161912
[ 17.889616] hardirqs last enabled at (161912): [<7bedfacf>]
__netdev_alloc_skb+0xcc/0x140
[ 17.897893] hardirqs last disabled at (161911): [<d58261d0>]
__netdev_alloc_skb+0x94/0x140
[ 17.904903] exynos5-hsi2c 12ca0000.i2c: tx timeout
[ 17.906116] softirqs last enabled at (161904): [<387102ff>]
irq_enter+0x78/0x80
[ 17.906123] softirqs last disabled at (161905): [<cf4c628e>]
irq_exit+0x134/0x158
[ 17.925722].
[ 17.925722] other info that might help us debug this:
[ 17.933435] Possible unsafe locking scenario:
[ 17.933435].
[ 17.940331] CPU0
[ 17.942488] ----
[ 17.944894] lock(&syncp->seq#5);
[ 17.948274] <Interrupt>
[ 17.950847] lock(&syncp->seq#5);
[ 17.954386].
[ 17.954386] *** DEADLOCK ***
[ 17.954386].
[ 17.962422] no locks held by swapper/0/0.
Fixes: c8b5d129ee29 ("net: usbnet: support 64bit stats")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Greg Ungerer <gerg@xxxxxxxxxxxxxx>
---
drivers/net/usb/usbnet.c | 10 ++++++----
include/linux/u64_stats_sync.h | 22 ++++++++++++++++++++++
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index 8a22ff67b0268a588428c61c6a6211e3c6c2a02a..d9eea8cfe6cb9a3bf8d0d4ce9198af9bccf9c757 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -315,6 +315,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
{
struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
+ unsigned long flags;
int status;
if (test_bit(EVENT_RX_PAUSED, &dev->flags)) {
@@ -326,10 +327,10 @@ void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
if (skb->protocol == 0)
skb->protocol = eth_type_trans (skb, dev->net);
- u64_stats_update_begin(&stats64->syncp);
+ flags = u64_stats_update_begin_irqsave(&stats64->syncp);
stats64->rx_packets++;
stats64->rx_bytes += skb->len;
- u64_stats_update_end(&stats64->syncp);
+ u64_stats_update_end_irqrestore(&stats64->syncp, flags);
netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
skb->len + sizeof (struct ethhdr), skb->protocol);
@@ -1248,11 +1249,12 @@ static void tx_complete (struct urb *urb)
if (urb->status == 0) {
struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
+ unsigned long flags;
- u64_stats_update_begin(&stats64->syncp);
+ flags = u64_stats_update_begin_irqsave(&stats64->syncp);
stats64->tx_packets += entry->packets;
stats64->tx_bytes += entry->length;
- u64_stats_update_end(&stats64->syncp);
+ u64_stats_update_end_irqrestore(&stats64->syncp, flags);
} else {
dev->net->stats.tx_errors++;
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 5bdbd9f49395f883ca2dc5aa0d7bbde11f379063..07ee0f84a46caa9e2b1c446f96009f63b3b99f50 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -90,6 +90,28 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
#endif
}
+static inline unsigned long
+u64_stats_update_begin_irqsave(struct u64_stats_sync *syncp)
+{
+ unsigned long flags = 0;
+
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+ local_irq_save(flags);
+ write_seqcount_begin(&syncp->seq);
+#endif
+ return flags;
+}
+
+static inline void
+u64_stats_update_end_irqrestore(struct u64_stats_sync *syncp,
+ unsigned long flags)
+{
+#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+ write_seqcount_end(&syncp->seq);
+ local_irq_restore(flags);
+#endif
+}
+
static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
--
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