Messages in this thread | | | Subject | Re: [PATCH] perf/x86/intel/rapl: Rename rapl_cpu_prepare() to rapl_cpu_starting() | From | Yasuaki Ishimatsu <> | Date | Tue, 24 Jan 2017 15:35:23 -0500 |
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Hi Thomas,
Thank you for your review.
I'm not familiar with the component. So I need your help to fix the issue.
Thanks, Yasuaki Ishimatsu
On 01/24/2017 02:54 PM, Thomas Gleixner wrote: > 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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