PR/56739 CVS commit: src/sys

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

The following reply was made to PR kern/56739; it has been noted by GNATS.

From: "Taylor R Campbell" <riastradh%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/56739 CVS commit: src/sys
Date: Wed, 9 Mar 2022 22:17:42 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Wed Mar  9 22:17:41 UTC 2022
 
 Modified Files:
 	src/sys/arch/mips/adm5120/dev: ahci.c
 	src/sys/dev/ic: sl811hs.c
 	src/sys/dev/usb: ehci.c motg.c ohci.c uhci.c usbdivar.h usbroothub.c
 	    xhci.c
 
 Log Message:
 usb: Provisionally release bus lock around ubm_rhctrl.
 
 This isn't quite correct, but it avoids a deadlock:
 
 - *_roothub_ctrl holds bus lock, waits in usb_delay_ms for kpause
 - softint waits for bus lock, holds up kpause wakeup
 
 The deadlock is new since recent changes to hold the bus lock over
 upm_start/upm_transfer.  Making this change regresses to other
 problems:
 
 - *_suspend/resume and *_roothub_ctrl often touch the same portsc
    registers
 
 - roothub_ctrl_abort needs to wait for ubm_rhctrl to complete.
 
   When the bus lock was held across both, a noop served here, but we
   can't hold the bus lock across both, so that doesn't work.
 
 However, these problems -- which we've had for a long time -- seem to
 be less bad than the deadlock.  So let's avoid the deadlock for now
 and then work out another way to serialize suspend/resume/rhctrl and
 aborts.
 
 Candidate fix for PR kern/56739.
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.30 -r1.31 src/sys/arch/mips/adm5120/dev/ahci.c
 cvs rdiff -u -r1.110 -r1.111 src/sys/dev/ic/sl811hs.c
 cvs rdiff -u -r1.305 -r1.306 src/sys/dev/usb/ehci.c
 cvs rdiff -u -r1.40 -r1.41 src/sys/dev/usb/motg.c
 cvs rdiff -u -r1.321 -r1.322 src/sys/dev/usb/ohci.c
 cvs rdiff -u -r1.311 -r1.312 src/sys/dev/usb/uhci.c
 cvs rdiff -u -r1.134 -r1.135 src/sys/dev/usb/usbdivar.h
 cvs rdiff -u -r1.13 -r1.14 src/sys/dev/usb/usbroothub.c
 cvs rdiff -u -r1.158 -r1.159 src/sys/dev/usb/xhci.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.