Sorry for delay, vacation. I'll try to re-read your email later, just one note for now...
On 07/27, Nikolay Borisov wrote: > > Based on that I think could be happening is that the sighand itself is > being freed while we are in the grace period inside __lock_task_sighand > but the slab page itself is not freed as per the semantics of > SLAB_DESTROY_BY_RCU. I looked up the source of this function in the > latest kernels and saw that Oleg had put a comment clarifying the > semantics but I'm still not convinced that it is safe. What if > we are trying to lock the spinlock before this particular slab is > initialised with sighand_ctor? But this is not possible? ->sighand can never point to the uninitialized struct sighand_struct. Just in case... please note that if ->sighand was freed and then re-allocated while __lock_task_sighand() spins under rcu_read_lock(), sighand_ctor() won't be called again (due to SLAB_DESTROY_BY_RCU). Perhaps this was the source of your confusion? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
