Messages in this thread | | | Date | Tue, 24 Jan 2017 20:54:12 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] perf/x86/intel/rapl: Rename rapl_cpu_prepare() to rapl_cpu_starting() |
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On Tue, 24 Jan 2017, Yasuaki Ishimatsu wrote: > rapl_cpu_prepare() must be called after logical package id of CPU > is set by topology_update_package_map(). > > But when onlining hot-added CPU, rapl_cpu_prepare() is called before > setting logical package id of the hot-added CPU. So cpu_to_rapl_pmu() > in rapl_cpu_prepare() finds a rapl_pmu of wrong logical package id and > rapl_cpu_prepare() initializes the wrong rapl_pmu. > > After that logical package id of the hot-added CPU is set by > topology_update_package_map(). But rapl_cpu_prepare() does > not initialize pmu of the logical package id of the hot-added CPU. > So when calling rapl_cpu_online(), cpu_to_rapl_pmu() returns NULL and > the following NULL pointer dereference occurs. > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > IP: rapl_cpu_online+0x8d/0xb0 > <snip> > Call Trace: > ? rapl_cpu_offline+0xc0/0xc0 > cpuhp_invoke_callback+0x8d/0x3f0 > cpuhp_up_callbacks+0x37/0xb0 > cpuhp_thread_fun+0xc9/0xe0 > smpboot_thread_fn+0x110/0x160 > kthread+0x101/0x140 > ? sort_range+0x30/0x30 > ? kthread_park+0x90/0x90 > ret_from_fork+0x25/0x30 > > The patch renames rapl_cpu_prepare() to rapl_cpu_starting() and changes > the position of cpuhp_state so that rapl_cpu_starting() is called > after topology_update_package_map().
Does not work. You cannot call that callback in the starting context. It does allocations. This needs be fixed in a different way. I'll have a look tomorrow.
Thanks,
tglx
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