Messages in this thread | | | Date | Tue, 22 Mar 2005 10:32:01 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-01 |
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* Ingo Molnar <mingo@elte.hu> wrote:
> seems to be a true SMP race: when i boot with 1 CPU it doesnt trigger, > the same kernel image and 2 CPUs triggers it on CPU#1. (CPU#0 is the > boot CPU) Note that the timing of the crash is not deterministic > (sometimes i get it during net startup, sometimes during ACPI > startup), but it always crashes within rcu_advance_callbacks(). > > one difference between your tests and mine is that your kernel is > doing _synchronize_kernel() from preempt-off sections (correct?), > while my kernel with PREEMPT_RT does it on preemptable sections.
hm, another thing: i think call_rcu() needs to take the read-lock. Right now it assumes that it has the data structure private, but that's only statistically true on PREEMPT_RT: another CPU may have this CPU's RCU control structure in use. So IRQs-off (or preempt-off) is not a guarantee to have the data structure, the read lock has to be taken.
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