Re: kern/52126 (mvsata Marvell 88SX6081 panics on boot)

[Frank Kardel <kardel%netbsd.org@localhost>]

The following reply was made to PR kern/52126; it has been noted by GNATS.

From: Frank Kardel <kardel%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/52126 (mvsata Marvell 88SX6081 panics on boot)
Date: Sat, 21 Dec 2019 07:56:19 +0100

 I was just referring to place where the flag is set, not that it is 
 related to mounting the root although attempting to exec init implies 
 the availability of the root.
 
 Crude indeed it is, es. It panics only during kernel startup when no 
 user code can be running,
 
 Maybe I am missing omething, but the prerequisite condition for panic is 
 "!start_init_exec". Maybe the test was intended to be inverted so that 
 the crude
 
 deadlock check is enabled while user level is running. Right now it only 
 checks during the initialization phase *before*
 
 user-level is running and in some circumstance even prohibits a 
 successful boot (slow raster console+debug+verbose boot).
 
 Frank
 
 On 12/20/19 23:40, Michael van Elst wrote:
 > The following reply was made to PR kern/52126; it has been noted by GNATS.
 >
 > From: mlelstv%serpens.de@localhost (Michael van Elst)
 > To: gnats-bugs%netbsd.org@localhost
 > Cc:
 > Subject: Re: kern/52126 (mvsata Marvell 88SX6081 panics on boot)
 > Date: Fri, 20 Dec 2019 22:34:41 -0000 (UTC)
 >
 >   kardel%kardel.name@localhost (Frank Kardel) writes:
 >   
 >   >The _kernel_lock() code looks very suspicious.
 >   
 >   >spinouts on kernel_lock only happen while the root is not mounted
 >   >(start_init_exec == 0, see init_main.c):
 >   
 >   start_init_exec is not related to the root mount but is set before the
 >   first user code is executed.
 >   
 >   The spinout check is a crude deadlock detection. It's not reasonable
 >   to do that for user code that is waiting to enter the kernel.
 >   
 >   If you want to remove the panic you may want to replace it with a (rate
 >   limited) console message.
 >   
 >   --
 >   --
 >                                   Michael van Elst
 >   Internet: mlelstv%serpens.de@localhost
 >                                   "A potential Snark may lurk in every tree."
 >