On Thu, Mar 7, 2013 at 9:35 PM, Ming Lei <tom.leim...@gmail.com> wrote: > Commit 14318efb(ARM: 7587/1: implement optimized percpu variable access) > introduces arm's __my_cpu_offset to optimize percpu vaiable access, > which really works well on hackbench, but will cause __my_cpu_offset > to return garbage value before it is initialized in cpu_init() called > by setup_arch, so accessing percpu variable before setup_arch may cause > kernel hang. But generic __my_cpu_offset always returns zero before > percpu area is brought up, and won't hang kernel. > > So the patch tries to clear __my_cpu_offset on boot CPU early > to avoid boot hang. > > At least now percpu variable is accessed by lockdep before > setup_arch(), and enabling CONFIG_LOCK_STAT or CONFIG_DEBUG_LOCKDEP > can trigger kernel hang. > > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: Rob Herring <rob.herr...@calxeda.com> > Cc: Will Deacon <will.dea...@arm.com> > Cc: Nicolas Pitre <n...@linaro.org> > Cc: Russell King <rmk+ker...@arm.linux.org.uk> > Signed-off-by: Ming Lei <tom.leim...@gmail.com> > --- > V1: > - documents lockdep uses percpu variable early
Looks no one objects the patch, so I has submitted it into Russell's patch system, and hope it can be pushed to linus tree soon and make LOCK_STAT/DEBUG_LOCKDEP usable on ARMv7. Thanks, -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
