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

[mlelstv%serpens.de@localhost (Michael van Elst)]

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: Sat, 21 Dec 2019 07:47:12 -0000 (UTC)

 kardel%netbsd.org@localhost (Frank Kardel) writes:
 
 > 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*
 
 Excessive waiting for the kernel lock is always a problem, functional
 (i.e. delayed interrupt processing and then lost interrupts) or just
 performance. But after bootstrap a panic is probably too much, anything
 before can be handled by just fixing the code that holds the kernel
 lock for too long.
 
 > user-level is running and in some circumstance even prohibits a 
 > successful boot (slow raster console+debug+verbose boot).
 
 This just shows that slow raster consoles (kernel messages, not tty) have
 their limitations. Still a good thing to get this information because
 it points to a design problem (kernel lock held too long) usually somewhere
 else. E.g. sdmmc(4) now sleeps in some places instead of spinning in delay()
 because of this.
 
 There are places in our ata code (and probably mvsata too) that need
 similar attention.
 
 -- 
 -- 
                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."