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net: usbnet: fix potential deadlock on 32bit hosts

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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@google.com>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-03-05 11:41:13 -08:00 committed by David S. Miller
parent 35d889d10b
commit 2695578b89
2 changed files with 28 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/net/usb/usbnet.c
View File

@ -315,6 +315,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev)
void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb) void usbnet_skb_return (struct usbnet *dev, struct sk_buff *skb)
{ {
struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64); struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64);
unsigned long flags;
int status; int status;
if (test_bit(EVENT_RX_PAUSED, &dev->flags)) { 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) if (skb->protocol == 0)
skb->protocol = eth_type_trans (skb, dev->net); 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_packets++;
stats64->rx_bytes += skb->len; 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", netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n",
skb->len + sizeof (struct ethhdr), skb->protocol); skb->len + sizeof (struct ethhdr), skb->protocol);
@ -1248,11 +1249,12 @@ static void tx_complete (struct urb *urb)
if (urb->status == 0) { if (urb->status == 0) {
struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->stats64); 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_packets += entry->packets;
stats64->tx_bytes += entry->length; stats64->tx_bytes += entry->length;
u64_stats_update_end(&stats64->syncp); u64_stats_update_end_irqrestore(&stats64->syncp, flags);
} else { } else {
dev->net->stats.tx_errors++; dev->net->stats.tx_errors++;

22
include/linux/u64_stats_sync.h
View File

@ -90,6 +90,28 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
#endif #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) static inline void u64_stats_update_begin_raw(struct u64_stats_sync *syncp)
{ {
#if BITS_PER_LONG==32 && defined(CONFIG_SMP) #if BITS_PER_LONG==32 && defined(CONFIG_SMP)