Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-02 Thread Tom Herbert
On Fri, Sep 2, 2016 at 11:13 AM, Brenden Blanco wrote: > On Mon, Aug 29, 2016 at 10:46:38AM -0700, Tom Herbert wrote: > [...] >> Brenden, tracking down how the structure is freed needed a few steps, >> please make sure the RCU requirements are well documented. Also, I'm >

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-02 Thread Brenden Blanco
On Mon, Aug 29, 2016 at 10:46:38AM -0700, Tom Herbert wrote: [...] > Brenden, tracking down how the structure is freed needed a few steps, > please make sure the RCU requirements are well documented. Also, I'm Really? It's just bpf_prog_put->call_rcu(__bpf_prog_put_rcu). I suppose what's missing

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-02 Thread Brenden Blanco
On Fri, Sep 02, 2016 at 01:59:40AM +0300, Saeed Mahameed wrote: > On Wed, Aug 31, 2016 at 4:50 AM, Brenden Blanco wrote: > > On Tue, Aug 30, 2016 at 12:35:58PM +0300, Saeed Mahameed wrote: [...] > >> Sorry folks I am with Tariq on this, you can't just add a single > >>

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-02 Thread Brenden Blanco
On Thu, Sep 01, 2016 at 04:30:28PM -0700, Tom Herbert wrote: [...] > > Yep, but this is an unlikely condition and the critical code here is > > much smaller and it is more clear that the rcu_read_lock here meant to > > protect the ring->xdp_prog under this small xdp critical section in > >

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-01 Thread Tom Herbert
On Thu, Sep 1, 2016 at 3:59 PM, Saeed Mahameed wrote: > On Wed, Aug 31, 2016 at 4:50 AM, Brenden Blanco wrote: >> On Tue, Aug 30, 2016 at 12:35:58PM +0300, Saeed Mahameed wrote: >>> On Mon, Aug 29, 2016 at 8:46 PM, Tom Herbert

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-09-01 Thread Saeed Mahameed
On Wed, Aug 31, 2016 at 4:50 AM, Brenden Blanco wrote: > On Tue, Aug 30, 2016 at 12:35:58PM +0300, Saeed Mahameed wrote: >> On Mon, Aug 29, 2016 at 8:46 PM, Tom Herbert wrote: >> > On Mon, Aug 29, 2016 at 8:55 AM, Brenden Blanco

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-30 Thread Brenden Blanco
On Tue, Aug 30, 2016 at 12:35:58PM +0300, Saeed Mahameed wrote: > On Mon, Aug 29, 2016 at 8:46 PM, Tom Herbert wrote: > > On Mon, Aug 29, 2016 at 8:55 AM, Brenden Blanco > > wrote: > >> On Mon, Aug 29, 2016 at 05:59:26PM +0300, Tariq Toukan wrote: >

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-30 Thread Saeed Mahameed
On Mon, Aug 29, 2016 at 8:46 PM, Tom Herbert wrote: > On Mon, Aug 29, 2016 at 8:55 AM, Brenden Blanco wrote: >> On Mon, Aug 29, 2016 at 05:59:26PM +0300, Tariq Toukan wrote: >>> Hi Brenden, >>> >>> The solution direction should be XDP specific that

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-29 Thread Tariq Toukan
Hi Brenden, The solution direction should be XDP specific that does not hurt the regular flow. On 26/08/2016 11:38 PM, Brenden Blanco wrote: Depending on the preempt mode, the bpf_prog stored in xdp_prog may be freed despite the use of call_rcu inside bpf_prog_put. The situation is possible

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-29 Thread Tom Herbert
On Mon, Aug 29, 2016 at 8:55 AM, Brenden Blanco wrote: > On Mon, Aug 29, 2016 at 05:59:26PM +0300, Tariq Toukan wrote: >> Hi Brenden, >> >> The solution direction should be XDP specific that does not hurt the >> regular flow. > An rcu_read_lock is _already_ taken for _every_

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-29 Thread Brenden Blanco
On Mon, Aug 29, 2016 at 05:59:26PM +0300, Tariq Toukan wrote: > Hi Brenden, > > The solution direction should be XDP specific that does not hurt the > regular flow. An rcu_read_lock is _already_ taken for _every_ packet. This is 1/64th of that. > > On 26/08/2016 11:38 PM, Brenden Blanco wrote: >

Re: [PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-26 Thread Brenden Blanco
On Fri, Aug 26, 2016 at 01:38:08PM -0700, Brenden Blanco wrote: > Depending on the preempt mode, the bpf_prog stored in xdp_prog may be > freed despite the use of call_rcu inside bpf_prog_put. The situation is > possible when running in PREEMPT_RCU=y mode, for instance, since the rcu > callback

[PATCH] net/mlx4_en: protect ring->xdp_prog with rcu_read_lock

2016-08-26 Thread Brenden Blanco
Depending on the preempt mode, the bpf_prog stored in xdp_prog may be freed despite the use of call_rcu inside bpf_prog_put. The situation is possible when running in PREEMPT_RCU=y mode, for instance, since the rcu callback for destroying the bpf prog can run even during the bh handling in the