* Ingo Molnar <[EMAIL PROTECTED]> 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. Ingo - 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/