Re: more barriers: Re: [PATCH 1/2] printk: add lockless buffer

2020-03-13 Thread John Ogness
Hi, This is quite a long response. I can summarize here: - Several new memory barrier pairs were identified. - The placement of a memory barrier was incorrect. There are now quite a few changes queued up for v2. I will try to get this posted soon. Also, I believe we've now identified the

Re: more barriers: Re: [PATCH 1/2] printk: add lockless buffer

2020-03-04 Thread Petr Mladek
On Thu 2020-02-27 13:04:09, John Ogness wrote: > On 2020-02-21, Petr Mladek wrote: > > If I get it correctly, the used cmpxchg_relaxed() variants does not > > provide full barriers. They are just able to prevent parallel > > manipulation of the modified variable. > > Correct. > > I purposely

Re: more barriers: Re: [PATCH 1/2] printk: add lockless buffer

2020-02-27 Thread John Ogness
On 2020-02-21, Petr Mladek wrote: > If I get it correctly, the used cmpxchg_relaxed() variants does not > provide full barriers. They are just able to prevent parallel > manipulation of the modified variable. Correct. I purposely avoided the full barriers of a successful cmpxchg() so that we