When CPU hotplug is run along with suspend/hibernate tests using the pm_test framework, even at the freezer level, we hit task freezing failures. One such failure was reported here: https://lkml.org/lkml/2011/9/5/28 An excerpt of the log: Freezing of tasks failed after 20.01 seconds (2 tasks refusing to freeze, wq_busy=0): invert_cpu_stat D 0000000000000000 5304 20435 17329 0x00000084 ffff8801f367bab8 0000000000000046 ffff8801f367bfd8 00000000001d3a00 ffff8801f367a010 00000000001d3a00 00000000001d3a00 00000000001d3a00 ffff8801f367bfd8 00000000001d3a00 ffff880414cc6840 ffff8801f36783c0 Call Trace: [<ffffffff81532de5>] schedule_timeout+0x235/0x320 [<ffffffff81532a0b>] wait_for_common+0x11b/0x170 [<ffffffff81532b3d>] wait_for_completion+0x1d/0x20 [<ffffffff81364486>] _request_firmware+0x156/0x2c0 [<ffffffff81364686>] request_firmware+0x16/0x20 [<ffffffffa01f0da0>] request_microcode_fw+0x70/0xf0 [microcode] [<ffffffffa01f0390>] microcode_init_cpu+0xc0/0x100 [microcode] [<ffffffffa01f14b4>] mc_cpu_callback+0x7c/0x11f [microcode] [<ffffffff815393a4>] notifier_call_chain+0x94/0xd0 [<ffffffff8109770e>] __raw_notifier_call_chain+0xe/0x10 [<ffffffff8106d000>] __cpu_notify+0x20/0x40 [<ffffffff8152cf5b>] _cpu_up+0xc7/0x10e [<ffffffff8152d07b>] cpu_up+0xd9/0xec [<ffffffff8151e599>] store_online+0x99/0xd0 [<ffffffff81355eb0>] sysdev_store+0x20/0x30 [<ffffffff811f3096>] sysfs_write_file+0xe6/0x170 [<ffffffff8117ee50>] vfs_write+0xd0/0x1a0 [<ffffffff8117f024>] sys_write+0x54/0xa0 [<ffffffff8153df02>] system_call_fastpath+0x16/0x1b The reason behind this failure is explained below: The x86 microcode update driver has callbacks registered for CPU hotplug events such as a CPU getting offlined or onlined. Things go wrong when a CPU hotplug stress test is carried out along with a suspend/resume operation running simultaneously. Upon getting a CPU_DEAD notification (for example, when a CPU offline occurs with tasks not frozen), the microcode callback frees up the microcode and invalidates it. Later, when that CPU gets onlined with tasks being frozen, the microcode callback (for the CPU_ONLINE_FROZEN event) tries to apply the microcode to the CPU; doesn't find it and hence depends on the (currently frozen) userspace to get the microcode again. This leads to the numerous "WARNING"s at drivers/base/firmware_class.c which eventually leads to task freezing failures in the suspend code path, as has been reported. So, this patch series addresses this issue by ensuring that CPU hotplug and suspend/hibernate don't run in parallel, thereby fixing the task freezing failures. v2: Implemented mutual exclusion between CPU hotplug and suspend/hibernate. Srivatsa S. Bhat (3): Introduce helper functions Mutually exclude cpu online and suspend/hibernate Update documentation Documentation/power/freezing-of-tasks.txt | 22 ++++++++++++++++++++++ include/linux/suspend.h | 21 +++++++++++++++++++-- kernel/cpu.c | 10 ++++++++++ 3 files changed, 51 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
