On Tue, 2014-01-21 at 15:51 +0100, Peter Zijlstra wrote: > On Tue, Jan 21, 2014 at 03:01:13PM +0100, Peter Zijlstra wrote: > > On Tue, Jan 21, 2014 at 02:02:06PM +0100, Jan Kiszka wrote: > > > Hi all, > > > > > > while trying to plug a race in the CPU hotplug code on xAPIC systems, I > > > was analyzing IPI transmission patterns. The handlers in > > > arch/x86/include/asm/ipi.h first wait for ICR, then send. In contrast, > > > arch_irq_work_raise sends the self-IPI directly and then waits. This > > > looks inconsistent. Is it intended? > > > > > > BTW, the races are in wakeup_secondary_cpu_via_init and > > > wakeup_secondary_cpu_via_nmi (lacking IRQ disable around ICR accesses). > > > There we also send first, then wait for completion. But I guess that is > > > due to the code originally only being used during boot. Will send fixes > > > for those once the sync pattern is clear to me. > > > > Could be I had no clue what I was doing and copy/pasted the code until > > it compiled and ran. > > > > In fact, I've got no clue what an ICR is. > > I dug about a bit, I borrowed that code from: > > lkml.kernel.org/r/[email protected] > > Huang Ying, can you explain to Jan why you do the wait afterwards?
I borrow the code from the original MCE report event code. Andi, could you help us to explain it? Best Regards, Huang Ying -- 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/
