On Tue 22-11-11 20:30:01, Wu Fengguang wrote: > > > @@ -1743,6 +1738,8 @@ void account_page_dirtied(struct page *p > > > __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); > > > task_dirty_inc(current); > > > task_io_account_write(PAGE_CACHE_SIZE); > > > + current->nr_dirtied++; > > > + __get_cpu_var(bdp_ratelimits)++; > > I think you need preempt_disable() and preempt_enable() pair around > > __get_cpu_var(). Otherwise a process could get rescheduled in the middle of > > read-modify-write cycle... > > Hmm, I'm not worried about it at all, because bdp_ratelimits don't > need to be accurate. In normal cases it won't even trigger one single > call to balance_dirty_pages(). I agree regarding the accuracy. But the CPU can change when the process is scheduled again. So you could modify counter of a CPU you are not running on. And that can cause bad things... > btw, account_page_dirtied() is called inside spinlock, will it be > sufficient? Currently it is not enough in real-time kernels and when sleeping spinlocks work gets merged it won't be enough even in standard kernels... And in kernels where spinlock means preemption is disabled preempt_enable/disable will be almost for free... Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
