x86/smpboot: Make optimization of delay calibration work correctly

commit 76ce7cfe35ef58f34e6ba85327afb5fbf6c3ff9b upstream.

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
Link: https://lkml.kernel.org/r/20171028001100.26603-1-pasha.tatashin@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 36171bcd91f81c30982a0c0b826588ed19d0cde9..9fe7b9e1ae3056d737ab6f55bfec41b8c1123c85 100644 (file)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -180,6 +180,12 @@ 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
@@ -190,11 +196,6 @@ 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 6e57edf33d758c1c451a5088143f1c7b5e91a154..44bf5cf417d34fd5372868c4d4cf3969510982c5 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1382,12 +1382,10 @@ 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);