From fcb43042ef55d2f46b0efa5d7746967cef38f056 Mon Sep 17 00:00:00 2001 From: "Zhang, Yanmin" Date: Tue, 24 Jun 2008 16:06:23 +0800 Subject: [PATCH] x86: fix cpu hotplug crash Vegard Nossum reported crashes during cpu hotplug tests: http://marc.info/?l=linux-kernel&m=121413950227884&w=4 In function _cpu_up, the panic happens when calling __raw_notifier_call_chain at the second time. Kernel doesn't panic when calling it at the first time. If just say because of nr_cpu_ids, that's not right. By checking the source code, I found that function do_boot_cpu is the culprit. Consider below call chain: _cpu_up=>__cpu_up=>smp_ops.cpu_up=>native_cpu_up=>do_boot_cpu. So do_boot_cpu is called in the end. In do_boot_cpu, if boot_error==true, cpu_clear(cpu, cpu_possible_map) is executed. So later on, when _cpu_up calls __raw_notifier_call_chain at the second time to report CPU_UP_CANCELED, because this cpu is already cleared from cpu_possible_map, get_cpu_sysdev returns NULL. Many resources are related to cpu_possible_map, so it's better not to change it. Below patch against 2.6.26-rc7 fixes it by removing the bit clearing in cpu_possible_map. Signed-off-by: Zhang Yanmin Tested-by: Vegard Nossum Acked-by: Rusty Russell Signed-off-by: Ingo Molnar --- arch/x86/kernel/smpboot.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 56078d61c793..3e1cecedde42 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -996,7 +996,6 @@ do_rest: #endif cpu_clear(cpu, cpu_callout_map); /* was set by do_boot_cpu() */ cpu_clear(cpu, cpu_initialized); /* was set by cpu_init() */ - cpu_clear(cpu, cpu_possible_map); cpu_clear(cpu, cpu_present_map); per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID; } -- 2.20.1