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List:       dragonfly-bugs
Subject:    [DragonFlyBSD - Bug #2353] panic: assertion "gd->gd_spinlocks_wr == 0" failed in bsd4_schedulerclock
From:       Venkatesh Srinivas via Redmine <bugtracker-admin () leaf ! dragonflybsd ! org>
Date:       2012-05-19 5:13:34
Message-ID: redmine.journal-10834.20120518221334 () leaf ! dragonflybsd ! org
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Issue #2353 has been updated by Venkatesh Srinivas.


Okay,

The problem is that we hold an MTX spinlock while attempting to go to sleep. The \
specific callpath and problem is that we hold the syscons MTX spinlock at :769, :771 \
of sys/dev/misc/syscons/syscons.c, around a device ioctl routine which may explicitly \
tsleep. The specific tsleep in question is via sysmouse_event, ultimately hitting \
kern_kevent and sleeping in kqueue.

First, why are we using MTX spinlocks at all?

Second, it is probably inappropriate to hold an MTX spinlock around the entire ioctl \
path here. The path gets the tty_token, among many other things, the chances of \
blocking are high.

What is it synchronizing that the tty_token is not?


----------------------------------------
Bug #2353: panic: assertion "gd->gd_spinlocks_wr == 0" failed in bsd4_schedulerclock
http://bugs.dragonflybsd.org/issues/2353

Author: Joachim de Groot
Status: New
Priority: Normal
Assignee: 
Category: 
Target version: 


Version String: DragonFly v3.1.0.322.gc231b-DEVELOPMENT #0: Fri Mar 16 20:31:33 CET \
2012

#0  _get_mycpu () at ./machine/thread.h:69
#1  md_dumpsys (di=<optimized out>) at \
/usr/src/sys/platform/pc64/x86_64/dump_machdep.c:263 #2  0xffffffff802fb2d2 in \
dumpsys () at /usr/src/sys/kern/kern_shutdown.c:937 #3  0xffffffff802fb936 in boot \
(howto=260) at /usr/src/sys/kern/kern_shutdown.c:387 #4  0xffffffff802fbbed in panic \
(fmt=0xffffffff80585cf0 "assertion \"%s\" failed in %s at %s:%u") at \
/usr/src/sys/kern/kern_shutdown.c:843 #5  0xffffffff803036fb in bsd4_schedulerclock \
(lp=<optimized out>, period=<optimized out>, cpstamp=<optimized out>) at \
/usr/src/sys/kern/usched_bsd4.c:622 #6  0xffffffff802db16c in schedclock \
(info=0xffffffff820106e8, in_ipi=<optimized out>, frame=<optimized out>) at \
/usr/src/sys/kern/kern_clock.c:776 #7  0xffffffff802f9e03 in systimer_intr \
(timep=<optimized out>, in_ipi=<optimized out>, frame=0x0) at \
/usr/src/sys/kern/kern_systimer.c:102 #8  0xffffffff8054ad04 in \
lapic_timer_process_oncpu (gd=0xffffffff8200f000, frame=0x0) at \
/usr/src/sys/platform/pc64/apic/lapic.c:336 #9  0xffffffff8054ad3c in \
lapic_timer_process () at /usr/src/sys/platform/pc64/apic/lapic.c:342 #10 \
0xffffffff80540d69 in splz_timer () at /usr/src/sys/platform/pc64/x86_64/ipl.s:461 \
#11 0x0000000000000000 in ?? ()

Before dumping, several text blocks like this one were emitted:

Fatal trap 12: page fault while in kernel mode
cpuid = 0; lapic->id = 00000000
fault virtual address   = 0x20
fault code              = supervisor write data, page not present
instruction pointer     = 0x8:0xffffffff802ec7fc
stack pointer           = 0x10:0xffffffe0a8b4a980
frame pointer           = 0x10:0xffffffe0a8b4a9c8
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 0, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 8139
current thread          = pri 6 (CRIT)
kernel: type 12 trap, code=2

A dump is available.


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