search for: smb_wmb

Users of ptr_ring expect that it's safe to give the data structure a pointer and have it be available to consumers, but that actually requires an smb_wmb or a stronger barrier. In absence of such barriers and on architectures that reorder writes, consumer might read an un=initialized value from an skb pointer stored in the skb array. This was observed causing crashes. To fix, add memory barriers. The barrier we use is a wmb, the assumption being...

Users of ptr_ring expect that it's safe to give the data structure a pointer and have it be available to consumers, but that actually requires an smb_wmb or a stronger barrier. In absence of such barriers and on architectures that reorder writes, consumer might read an un=initialized value from an skb pointer stored in the skb array. This was observed causing crashes. To fix, add memory barriers. The barrier we use is a wmb, the assumption being...

...d, Dec 06, 2017 at 10:31:39AM +0800, Jason Wang wrote: > > > On 2017?12?06? 03:29, Michael S. Tsirkin wrote: > > Users of ptr_ring expect that it's safe to give the > > data structure a pointer and have it be available > > to consumers, but that actually requires an smb_wmb > > or a stronger barrier. > > > > In absence of such barriers and on architectures that reorder writes, > > consumer might read an un=initialized value from an skb pointer stored > > in the skb array. This was observed causing crashes. > > > > To fix, a...

...d, Dec 06, 2017 at 10:31:39AM +0800, Jason Wang wrote: > > > On 2017?12?06? 03:29, Michael S. Tsirkin wrote: > > Users of ptr_ring expect that it's safe to give the > > data structure a pointer and have it be available > > to consumers, but that actually requires an smb_wmb > > or a stronger barrier. > > > > In absence of such barriers and on architectures that reorder writes, > > consumer might read an un=initialized value from an skb pointer stored > > in the skb array. This was observed causing crashes. > > > > To fix, a...

On 2017?12?06? 03:29, Michael S. Tsirkin wrote: > Users of ptr_ring expect that it's safe to give the > data structure a pointer and have it be available > to consumers, but that actually requires an smb_wmb > or a stronger barrier. > > In absence of such barriers and on architectures that reorder writes, > consumer might read an un=initialized value from an skb pointer stored > in the skb array. This was observed causing crashes. > > To fix, add memory barriers. The barrier we u...

From: "Michael S. Tsirkin" <mst at redhat.com> Date: Tue, 5 Dec 2017 21:29:37 +0200 > Users of ptr_ring expect that it's safe to give the > data structure a pointer and have it be available > to consumers, but that actually requires an smb_wmb > or a stronger barrier. > > In absence of such barriers and on architectures that reorder writes, > consumer might read an un=initialized value from an skb pointer stored > in the skb array. This was observed causing crashes. > > To fix, add memory barriers. The barrier we...

Hi Michael, On 12/06/2017 12:59 AM, Michael S. Tsirkin wrote: > Users of ptr_ring expect that it's safe to give the > data structure a pointer and have it be available > to consumers, but that actually requires an smb_wmb > or a stronger barrier. This is not the exact situation we are seeing. Let me try to explain the situation Affected on ARM64 platform. 1) tun_net_xmit calls skb_array_produce, which pushes the skb to the ptr_ring, this push is protected by a producer_lock. 2)Prior to this call the tun_net_xm...

...1:41PM +0530, George Cherian wrote: > Hi Michael, > > > On 12/06/2017 12:59 AM, Michael S. Tsirkin wrote: > > Users of ptr_ring expect that it's safe to give the > > data structure a pointer and have it be available > > to consumers, but that actually requires an smb_wmb > > or a stronger barrier. > This is not the exact situation we are seeing. Could you test the patch pls? > Let me try to explain the situation > > Affected on ARM64 platform. > 1) tun_net_xmit calls skb_array_produce, which pushes the skb to the > ptr_ring, this push is...