Author: kib
Date: Mon Jan 20 17:23:03 2020
New Revision: 356919
URL: https://svnweb.freebsd.org/changeset/base/356919

Log:
  x86: Wait for curthread to be set up as an indicator that the boot stack
  is no longer used.
  
  pc_curthread is set by cpu_switch after it stopped using the old
  thread (or boot) stack.  This makes the smp_after_idle_runnable()
  function not dependent on the internals of the scheduler operations.
  
  Reviewed by:  markj
  Sponsored by: The FreeBSD Foundation
  MFC after:    1 week
  Differential revision:        https://reviews.freebsd.org/D23276

Modified:
  head/sys/x86/x86/mp_x86.c

Modified: head/sys/x86/x86/mp_x86.c
==============================================================================
--- head/sys/x86/x86/mp_x86.c   Mon Jan 20 16:59:39 2020        (r356918)
+++ head/sys/x86/x86/mp_x86.c   Mon Jan 20 17:23:03 2020        (r356919)
@@ -1092,13 +1092,12 @@ init_secondary_tail(void)
 static void
 smp_after_idle_runnable(void *arg __unused)
 {
-       struct thread *idle_td;
+       struct pcpu *pc;
        int cpu;
 
        for (cpu = 1; cpu < mp_ncpus; cpu++) {
-               idle_td = pcpu_find(cpu)->pc_idlethread;
-               while (atomic_load_int(&idle_td->td_lastcpu) == NOCPU &&
-                   atomic_load_int(&idle_td->td_oncpu) == NOCPU)
+               pc = pcpu_find(cpu);
+               while (atomic_load_ptr(&pc->pc_curthread) == (uintptr_t)NULL)
                        cpu_spinwait();
                kmem_free((vm_offset_t)bootstacks[cpu], kstack_pages *
                    PAGE_SIZE);
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