From dc1829a4c378d793fb3b95d56135d89a0d7ff72a Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 17 Nov 2006 14:26:18 +0100 Subject: [PATCH] i386/x86_64: ACPI cpu_idle_wait() fix The scheduler on Andreas Friedrich's hyperthreading system stopped working properly: the scheduler would never move tasks to another CPU! The lask known working kernel was 2.6.8. After a couple of attempts to corner the bug, the following smoking gun was found: BIOS reported wrong ACPI idfor the processor CPU#1: set_cpus_allowed(), swapper:1, 3 -> 2 [] show_trace_log_lvl+0x34/0x4a [] show_trace+0x2c/0x2e [] dump_stack+0x2b/0x2d [] set_cpus_allowed+0x52/0xec [] cpu_idle_wait+0x2e/0x100 [] acpi_processor_power_exit+0x45/0x58 [] acpi_processor_remove+0x46/0xea [] acpi_start_single_object+0x47/0x54 [] acpi_bus_register_driver+0xa4/0xd3 [] acpi_processor_init+0x57/0x77 [] init+0x146/0x2fd [] kernel_thread_helper+0x7/0x10 a quick look at cpu_idle_wait() shows how broken that code is on i386: it changes the init task's affinity map but never restores it ... and because all userspace tasks get forked by init, they all inherited that single-CPU affinity mask. x86_64 cloned this bug too. Signed-off-by: Ingo Molnar Cc: Andreas Friedrich Cc: Wolfgang Erig Cc: Andrew Morton Cc: Adrian Bunk Signed-off-by: Linus Torvalds --- arch/i386/kernel/process.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/i386') diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 1e1fa3e391a3..dd53c58f64f1 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -205,7 +205,7 @@ void cpu_idle(void) void cpu_idle_wait(void) { unsigned int cpu, this_cpu = get_cpu(); - cpumask_t map; + cpumask_t map, tmp = current->cpus_allowed; set_cpus_allowed(current, cpumask_of_cpu(this_cpu)); put_cpu(); @@ -227,6 +227,8 @@ void cpu_idle_wait(void) } cpus_and(map, map, cpu_online_map); } while (!cpus_empty(map)); + + set_cpus_allowed(current, tmp); } EXPORT_SYMBOL_GPL(cpu_idle_wait); -- cgit v1.2.3