On Wed, Sep 26, 2007 at 05:07:33PM -0400, Steven Rostedt wrote: > > -- > On Wed, 26 Sep 2007, Peter Zijlstra wrote: > > > > On Wed, 2007-09-26 at 12:55 -0700, Paul E. McKenney wrote: > > > > > Well, we could make spin_lock_irqsave() invoke rcu_read_lock() and > > > spin_lock_irqrestore() invoke rcu_read_unlock(), with similar adjustments > > > to the other primitives in this group. Then RCU priority boosting would > > > kick in if configured. > > > > Might be me, but 'hiding' the RCU scope like that makes my skin crawl. > > What is wrong with using rcu_read_lock() explicitly where you depend on > > it? It even makes the code cleaner in that it documents the usage. > > > > These blanket locks like lock_kernel(), preempt_disable(), > > local_irq_disable() etc. are very hard to get rid of because they don't > > document what is protected. > > > > Please lets not add to this mess and keep all this explicit. > > > > Yes, -rt changes the preemption model, and that has concequences. But > > IMHO the resulting code is cleaner in most cases. > > > > I'd go as far as to depricate synchronize_sched() and replace all its > > users with proper RCU. > > > > The more I think of it, the more I dislike this synchronize_all_irqs() > > and the 'magic' property of irq handlers. > > Thinking a little more about this, I fully agree with Peter. Again, it is not me that you need to convince. ;-) > What code needs to know that all spin_locks have released, or you want to > know all irq handlers are done? > > Seems that this is a broad data to ask for and will be a bitch to clean up > when we find out that this is not scalable. This all sounds like > reinventing the BKL. It would scale just fine, and inherently does not need priority boosting (since preempted/blocked things cannot hold up sychronize_sched()). That said, I do agree with you that having things explicit is a good thing. > If you simply want a RCU type of scheme, then simply use RCU. I second > deprecating "synchronize_sched". Everything that does RCU type locking > (that is waiting for some kind of grace period to finish) should simply > use RCU and not a "wait for all processes to voluntarily schedule" or > "wait for all interrupt handlers to finish". Here are the uses in 2.6.23-rc6. There are several that might not be so easy to replace with RCU. Thanx, Paul arch/i386/oprofile/nmi_timer_int.c timer_stop 55 synchronize_sched(); arch/x86_64/kernel/mce.c mce_read 607 synchronize_sched(); drivers/acpi/processor_idle.c acpi_processor_cst_has_changed 1132 synchronize_sched(); drivers/char/ipmi/ipmi_si_intf.c try_smi_init 2879 synchronize_sched(); drivers/char/sonypi.c sonypi_remove 1435 synchronize_sched(); drivers/input/keyboard/atkbd.c atkbd_disconnect 827 synchronize_sched(); drivers/input/serio/i8042.c i8042_stop 281 synchronize_sched(); drivers/net/r8169.c rtl8169_down 2866 synchronize_sched(); drivers/net/sis190.c sis190_down 1123 synchronize_sched(); drivers/s390/cio/airq.c s390_register_adapter_interrupt 46 synchronize_sched(); drivers/s390/cio/airq.c s390_unregister_adapter_interrupt 66 synchronize_sched(); kernel/kprobes.c check_safety 127 synchronize_sched(); kernel/kprobes.c unregister_kprobe 632 synchronize_sched(); kernel/kprobes.c disable_all_kprobes 970 synchronize_sched(); kernel/module.c sys_init_module 2013 synchronize_sched(); kernel/profile.c sys_init_module 195 synchronize_sched(); kernel/rcutorture.c sched_torture_synchronize 490 synchronize_sched(); kernel/sched.c detach_destroy_domains 6329 synchronize_sched(); kernel/srcu.c synchronize_srcu 176 synchronize_sched(); kernel/srcu.c synchronize_srcu 193 synchronize_sched(); kernel/srcu.c synchronize_srcu 206 synchronize_sched(); - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
