From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yinghai Lu Subject: [PATCH -v2] cpufreq: fix racing between acpi_cpufreq_loading Date: Fri, 20 Sep 2013 10:44:03 -0700 Message-ID: <1379699043-7414-1-git-send-email-yinghai@kernel.org> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" , Viresh Kumar Cc: cpufreq@vger.kernel.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Yinghai Lu List-Id: linux-pm@vger.kernel.org There is racing in __acpi_processor_start ==> acpi_processor_load_module ==> request_module_nowait/requested = 1 before first pr path to have requested set, second cpu would request again. that will cause acpi_cpufreq_early_init to be called in parallel, that will cause data curruption in acpi_cpufreq_early_init... and intermittent crash. So add mutex to protect it. Signed-off-by: Yinghai Lu --- drivers/acpi/processor_perflib.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) Index: linux-2.6/drivers/acpi/processor_perflib.c =================================================================== --- linux-2.6.orig/drivers/acpi/processor_perflib.c +++ linux-2.6/drivers/acpi/processor_perflib.c @@ -235,6 +235,7 @@ void acpi_processor_ppc_exit(void) acpi_processor_ppc_status &= ~PPC_REGISTERED; } +static DEFINE_MUTEX(acpi_cpufreq_load_lock); /* * Do a quick check if the systems looks like it should use ACPI * cpufreq. We look at a _PCT method being available, but don't @@ -246,8 +247,12 @@ void acpi_processor_load_module(struct a acpi_status status = 0; struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL }; - if (!arch_has_acpi_pdc() || requested) + mutex_lock(&acpi_cpufreq_load_lock); + if (!arch_has_acpi_pdc() || requested) { + mutex_unlock(&acpi_cpufreq_load_lock); return; + } + status = acpi_evaluate_object(pr->handle, "_PCT", NULL, &buffer); if (!ACPI_FAILURE(status)) { printk(KERN_INFO PREFIX "Requesting acpi_cpufreq\n"); @@ -255,6 +260,7 @@ void acpi_processor_load_module(struct a requested = 1; } kfree(buffer.pointer); + mutex_unlock(&acpi_cpufreq_load_lock); } static int acpi_processor_get_performance_control(struct acpi_processor *pr)