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Date:      Mon, 8 Feb 2021 14:01:59 +0100
From:      Hans Petter Selasky <hps@selasky.org>
To:        Alastair Hogge <agh@riseup.net>, Emmanuel Vadot <manu@bidouilliste.com>
Cc:        Steve Kargl <sgk@troutmask.apl.washington.edu>, Andriy Gapon <avg@freebsd.org>, freebsd-current@freebsd.org, freebsd-x11@freebsd.org
Subject:   Re: panic in drm or vt or deadlock on mutex or ...
Message-ID:  <fea61694-367d-7161-e071-4a8f77810a68@selasky.org>
In-Reply-To: <36a5927f9992ec828a0fe1e9bf480ce3@riseup.net>
References:  <20210203050828.GA21823@troutmask.apl.washington.edu> <4581b83f-e048-fb8b-edfe-44332d3dc460@FreeBSD.org> <20210203160324.GA23963@troutmask.apl.washington.edu> <20210204105029.5fc11bed5df0e4283f983fbf@bidouilliste.com> <36a5927f9992ec828a0fe1e9bf480ce3@riseup.net>

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[-- Attachment #1 --]
On 2/8/21 1:53 PM, Alastair Hogge wrote:
> Boot to multi-user; login (getty):
> $ doas kldload /boot/modules/amdgpu.ko
> $ sysctl
> [panic]
> 
> ..is a guaranteed way to panic my system.

Hi,

Maybe you could do a hack and edit the sysctl source code:

1) print the sysctl before it is queried.
2) sleep 1 second between print and query.

Should be easy to nail this down!

--HPS

[-- Attachment #2 --]
diff --git a/sbin/sysctl/sysctl.c b/sbin/sysctl/sysctl.c
index 30d6d94723f..4b45bb2f967 100644
--- a/sbin/sysctl/sysctl.c
+++ b/sbin/sysctl/sysctl.c
@@ -336,6 +336,10 @@ parse_numeric(const char *newvalstr, const char *fmt, u_int kind,
 	return (true);
 }
 
+#define	sysctl(...) ({ \
+  usleep(1000000); \
+  sysctl(__VA_ARGS__); })
+
 /*
  * Parse a name into a MIB entry.
  * Lookup and print out the MIB entry if it exists.
help

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