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authorEric Dumazet <edumazet@google.com>2021-03-19 10:39:33 -0700
committerDavid S. Miller <davem@davemloft.net>2021-03-19 13:38:46 -0700
commit919067cc845f323a80b6fe987b64238bd82d309e (patch)
treef8f639053de5df86f213fffa61268e75df05c07d /net
parent942f0c6e28edc627658732b9f225a602cbaa8f8e (diff)
downloadlinux-919067cc845f323a80b6fe987b64238bd82d309e.tar.bz2
net: add CONFIG_PCPU_DEV_REFCNT
I was working on a syzbot issue, claiming one device could not be dismantled because its refcount was -1 unregister_netdevice: waiting for sit0 to become free. Usage count = -1 It would be nice if syzbot could trigger a warning at the time this reference count became negative. This patch adds CONFIG_PCPU_DEV_REFCNT options which defaults to per cpu variables (as before this patch) on SMP builds. v2: free_dev label in alloc_netdev_mqs() is moved to avoid a compiler warning (-Wunused-label), as reported by kernel test robot <lkp@intel.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/Kconfig8
-rw-r--r--net/core/dev.c10
2 files changed, 18 insertions, 0 deletions
diff --git a/net/Kconfig b/net/Kconfig
index 0ead7ec0d2bd..9c456acc379e 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -245,6 +245,14 @@ source "net/l3mdev/Kconfig"
source "net/qrtr/Kconfig"
source "net/ncsi/Kconfig"
+config PCPU_DEV_REFCNT
+ bool "Use percpu variables to maintain network device refcount"
+ depends on SMP
+ default y
+ help
+ network device refcount are using per cpu variables if this option is set.
+ This can be forced to N to detect underflows (with a performance drop).
+
config RPS
bool
depends on SMP && SYSFS
diff --git a/net/core/dev.c b/net/core/dev.c
index 4961fc2e9b19..be941ed754ac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10312,11 +10312,15 @@ EXPORT_SYMBOL(register_netdev);
int netdev_refcnt_read(const struct net_device *dev)
{
+#ifdef CONFIG_PCPU_DEV_REFCNT
int i, refcnt = 0;
for_each_possible_cpu(i)
refcnt += *per_cpu_ptr(dev->pcpu_refcnt, i);
return refcnt;
+#else
+ return refcount_read(&dev->dev_refcnt);
+#endif
}
EXPORT_SYMBOL(netdev_refcnt_read);
@@ -10674,9 +10678,11 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
dev = PTR_ALIGN(p, NETDEV_ALIGN);
dev->padded = (char *)dev - (char *)p;
+#ifdef CONFIG_PCPU_DEV_REFCNT
dev->pcpu_refcnt = alloc_percpu(int);
if (!dev->pcpu_refcnt)
goto free_dev;
+#endif
if (dev_addr_init(dev))
goto free_pcpu;
@@ -10740,8 +10746,10 @@ free_all:
return NULL;
free_pcpu:
+#ifdef CONFIG_PCPU_DEV_REFCNT
free_percpu(dev->pcpu_refcnt);
free_dev:
+#endif
netdev_freemem(dev);
return NULL;
}
@@ -10783,8 +10791,10 @@ void free_netdev(struct net_device *dev)
list_for_each_entry_safe(p, n, &dev->napi_list, dev_list)
netif_napi_del(p);
+#ifdef CONFIG_PCPU_DEV_REFCNT
free_percpu(dev->pcpu_refcnt);
dev->pcpu_refcnt = NULL;
+#endif
free_percpu(dev->xdp_bulkq);
dev->xdp_bulkq = NULL;