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Message-ID: <20080527170611.GD14296@linux.vnet.ibm.com> Date: Tue, 27 May 2008 10:06:11 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Oleg Nesterov <oleg@...sign.ru>, Alexey Dobriyan <adobriyan@...il.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: 2.6.26-rc4: RIP find_pid_ns+0x6b/0xa0 On Tue, May 27, 2008 at 09:11:33AM -0700, Linus Torvalds wrote: > On Tue, 27 May 2008, Paul E. McKenney wrote: > > > > But this will only help until preemptible spinlocks arrive, right? > > I don't think we will ever have preemptible spinlocks. > > If you preempt spinlocks, you have serious issues with contention and > priority inversion etc, and you basically need to turn them into sleeping > mutexes. So now you also need to do interrupts as sleepable threads etc > etc. Indeed, all of these are required in that case. > And it would break the existing non-preempt RCU usage anyway. Yes, preemptable spinlocks cannot work without preemptable RCU. > Yeah, maybe the RT people try to do that, but quite frankly, it is insane. > Spinlocks are *different* from sleeping locks, for a damn good reason. Well, I guess I never claimed to be sane... Anyway, will look at a preemptable RCU that waits for preempt-disable sections of code. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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