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x86: Wait for curthread to be set up as an indicator that the boot stack

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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
This commit is contained in:
Konstantin Belousov 2020-01-20 17:23:03 +00:00
parent 6e4cafd1be
commit 65e5f2cdd4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=356919
1 changed files with 3 additions and 4 deletions
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7
sys/x86/x86/mp_x86.c
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@ -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);