> Author: jeff
> Date: Mon Dec 16 20:15:04 2019
> New Revision: 355819
> URL:
> https://svnweb.freebsd.org/changeset/base/355819
>
>
> Log:
> Repeat the spinlock_enter/exit pattern from amd64 on other architectures to
> fix an assert violation introduced in r355784. Without this spinlock_exit()
> may see owepreempt and switch before reducing the spinlock count. amd64
> had been optimized to do a single critical enter/exit regardless of the
> number of spinlocks which avoided the problem and this optimization had
> not been applied elsewhere.
>
> Reported by: emaste
> Suggested by: rlibby
> Discussed with: jhb, rlibby
> Tested by: manu (arm64)
>
> Modified:
> head/sys/arm/arm/machdep.c
> head/sys/arm64/arm64/machdep.c
> head/sys/i386/i386/machdep.c
> head/sys/mips/mips/machdep.c
> head/sys/powerpc/powerpc/machdep.c
> head/sys/riscv/riscv/machdep.c
It looks like sparc64 still has the old code structure:
>From /usr/src/sys/sparc64/sparc64/machdep.c . . .
void
spinlock_enter(void)
{
struct thread *td;
register_t pil;
td = curthread;
if (td->td_md.md_spinlock_count == 0) {
pil = rdpr(pil);
wrpr(pil, 0, PIL_TICK);
td->td_md.md_spinlock_count = 1;
td->td_md.md_saved_pil = pil;
} else
td->td_md.md_spinlock_count++;
critical_enter();
}
void
spinlock_exit(void)
{
struct thread *td;
register_t pil;
td = curthread;
critical_exit();
pil = td->td_md.md_saved_pil;
td->td_md.md_spinlock_count--;
if (td->td_md.md_spinlock_count == 0)
wrpr(pil, pil, 0);
}
(Not that I ever do anything with sparc64 machines.)
===
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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