Date: Mon, 8 Mar 2021 14:31:15 -0500 From: Ed Maste <emaste@freebsd.org> To: Kyle Evans <kevans@freebsd.org> Cc: Yasuhiro Kimura <yasu@utahime.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Waiting for bufdaemon Message-ID: <CAPyFy2D-c559fQTtF%2B5kE_tPt8dFqDSGuWr6GfpDkG1fykwCbA@mail.gmail.com> In-Reply-To: <CACNAnaHDTeDmNWXTSU4TzF9C_CUpT_3Vr3GgmhjSqWaGWtjXBg@mail.gmail.com> References: <CACNAnaEPJftb_1Jg94zpR4AoU5TKEjbXuYcAA0ByUmL0=hPQCg@mail.gmail.com> <YEVpwXGS5UBA8P44@kib.kiev.ua> <20210309.005732.1808108188909983665.yasu@utahime.org> <20210309.015021.2131122829257392547.yasu@utahime.org> <CACNAnaHDTeDmNWXTSU4TzF9C_CUpT_3Vr3GgmhjSqWaGWtjXBg@mail.gmail.com>
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On Mon, 8 Mar 2021 at 12:07, Kyle Evans <kevans@freebsd.org> wrote:
>
> diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
> index 68fc57e6ea7..6f25360a67c 100644
> --- a/sys/x86/x86/tsc.c
> +++ b/sys/x86/x86/tsc.c
> @@ -501,7 +501,12 @@ test_tsc(int adj_max_count)
> uint64_t *data, *tsc;
> u_int i, size, adj;
>
> - if ((!smp_tsc && !tsc_is_invariant) || vm_guest)
> + /*
> + * Misbehavior of TSC under VirtualBox has been observed. In
> + * particular, threads doing small (~1 second) sleeps may miss their
> + * wakeup and hang around in sleep state, causing hangs on shutdown.
> + */
> + if ((!smp_tsc && !tsc_is_invariant) || vm_guest == VM_GUEST_VBOX)
> return (-100);
> size = (mp_maxid + 1) * 3;
> data = malloc(sizeof(*data) * size * N, M_TEMP, M_WAITOK);
This seems like a sensible change to me. To make it explicilty clear
what the comment/workaround applies to, maybe rewrite it as:
if (!smp_tsc && !tsc_is_invariant)
return (-100);
/*
* Misbehavior of TSC under VirtualBox has been observed. In
* particular, threads doing small (~1 second) sleeps may miss their
* wakeup and hang around in sleep state, causing hangs on shutdown.
*/
if (vm_guest == VM_GUEST_VBOX)
return (-100);
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