Konrad Rzeszutek Wilk
2013-Mar-19 20:25 UTC
[PATCH] xen/acpi-processor: Don''t dereference struct acpi_processor on all CPUs.
With git commit c705c78c0d0835a4aa5d0d9a3422e3218462030c "acpi: Export the acpi_processor_get_performance_info" we are now using a different mechanism to access the P-states. The acpi_processor per-cpu structure is set and filtered by the core ACPI code which shrinks the per_cpu contents to only online CPUs. In the past we would call acpi_processor_register_performance() which would have not tried to dereference offline cpus. With the new patch and the fact that the loop we take is for for_all_possible_cpus we end up crashing on some machines. We could modify the loop to be for online_cpus - but all the other loops in the code use possible_cpus (for a good reason) - so lets leave it as so and just check if per_cpu(processor) is NULL. With this patch we will bypass the !online but possible CPUs. This fixes: IP: [<ffffffffa00d13b5>] xen_acpi_processor_init+0x1b6/0xe01 [xen_acpi_processor] PGD 4126e6067 PUD 4126e3067 PMD 0 Oops: 0002 [#1] SMP Pid: 432, comm: modprobe Not tainted 3.9.0-rc3+ #28 To be filled by O.E.M. To be filled by O.E.M./M5A97 RIP: e030:[<ffffffffa00d13b5>] [<ffffffffa00d13b5>] xen_acpi_processor_init+0x1b6/0xe01 [xen_acpi_processor] RSP: e02b:ffff88040c8a3ce8 EFLAGS: 00010282 .. snip.. Call Trace: [<ffffffffa00d11ff>] ? read_acpi_id+0x12b/0x12b [xen_acpi_processor] [<ffffffff8100215a>] do_one_initcall+0x12a/0x180 [<ffffffff810c42c3>] load_module+0x1cd3/0x2870 [<ffffffff81319b70>] ? ddebug_proc_open+0xc0/0xc0 [<ffffffff810c4f37>] sys_init_module+0xd7/0x120 [<ffffffff8166ce19>] system_call_fastpath+0x16/0x1b on some machines. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- drivers/xen/xen-acpi-processor.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/xen/xen-acpi-processor.c b/drivers/xen/xen-acpi-processor.c index f3278a6..90e34ac 100644 --- a/drivers/xen/xen-acpi-processor.c +++ b/drivers/xen/xen-acpi-processor.c @@ -505,6 +505,9 @@ static int __init xen_acpi_processor_init(void) pr = per_cpu(processors, i); perf = per_cpu_ptr(acpi_perf_data, i); + if (!pr) + continue; + pr->performance = perf; rc = acpi_processor_get_performance_info(pr); if (rc) -- 1.8.0.2