x86/smpboot: Make optimization of delay calibration work correctly

If the TSC has constant frequency then the delay calibration can be skipped
when it has been calibrated for a package already. This is checked in
calibrate_delay_is_known(), but that function is buggy in two aspects:

It returns 'false' if

  (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC)

which is obviously the reverse of the intended check and the check for the
sibling mask cannot work either because the topology links have not been
set up yet.

Correct the condition and move the call to set_cpu_sibling_map() before
invoking calibrate_delay() so the sibling check works correctly.

[ tglx: Rewrote changelong ]

Fixes: c25323c07345 ("x86/tsc: Use topology functions")
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: bob.picco@oracle.com
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20171028001100.26603-1-pasha.tatashin@oracle.com

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ad59edd84de70cfb978b8c0bc2ac38b892418b71..65a0ccdc3050742f9235922aaa3774560ca1f9c2 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -193,6 +193,12 @@ static void smp_callin(void)
         */
        smp_store_cpu_info(cpuid);
 
+       /*
+        * The topology information must be up to date before
+        * calibrate_delay() and notify_cpu_starting().
+        */
+       set_cpu_sibling_map(raw_smp_processor_id());
+
        /*
         * Get our bogomips.
         * Update loops_per_jiffy in cpu_data. Previous call to
@@ -203,11 +209,6 @@ static void smp_callin(void)
        cpu_data(cpuid).loops_per_jiffy = loops_per_jiffy;
        pr_debug("Stack at about %p\n", &cpuid);
 
-       /*
-        * This must be done before setting cpu_online_mask
-        * or calling notify_cpu_starting.
-        */
-       set_cpu_sibling_map(raw_smp_processor_id());
        wmb();
 
        notify_cpu_starting(cpuid);

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 796d96bb0821874a3b567d1b95f802b85f1222dc..ad2b925a808e7327dec37ae03c60ea2901d48352 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1346,12 +1346,10 @@ void __init tsc_init(void)
 unsigned long calibrate_delay_is_known(void)
 {
        int sibling, cpu = smp_processor_id();
-       struct cpumask *mask = topology_core_cpumask(cpu);
+       int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC);
+       const struct cpumask *mask = topology_core_cpumask(cpu);
 
-       if (!tsc_disabled && !cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC))
-               return 0;
-
-       if (!mask)
+       if (tsc_disabled || !constant_tsc || !mask)
                return 0;
 
        sibling = cpumask_any_but(mask, cpu);