SUMMARY: unhelpful error messages

From: Steve Elliott (
Date: Sat May 07 1994 - 17:19:46 CDT

I recently asked:
>Last night one of my systems, a SS10 with SunOS4.1.3,
>crashed with the following errors:
>mb_mapfree: MR == 0!!!
>mb_mapfree: MR == 0!!!
>mb_mapfree: MR == 0!!!
>panic on cpu0: tmp_rename

>Anyone able to decipher this? The system uses tmpfs, my suspicion
>is that /tmp filled up and bumped into the system trying to swap.
I got one reply:
        From: Joe Silva <jsilva@com.polaris1.rocknroll>
        Message-Id: <>
        Subject: Re: unhelpful error messages
        Cc: jsilva@COM.DMC
        Content-Type: X-sun-attachment
        Status: RO

        It appears you may have a software bug. See attached.


         Bug Id: 1029783
         Category: kernel
         Subcategory: driver
         Release summary: 4.1prebeta, 4.0.3
         Synopsis: mb_mapalloc can call back while driver 'protected' by spl.
                 Integrated in releases: 4.1
        There is a potential problem for drivers using mb_mapalloc() directly
        and expecting a callback in the case where resources aren't immediately

        The callback can occur while the driver is in its interrupt handler.

        This is because the callback routine is called by mb_mapfree, which
        can be called from the interrupt handler from another driver which
        has a higher priority.

        The scenario:

                Driver A calls mb_mapalloc(), DVMA is not available, so driver A's
                callback routine is queued.
                Driver A gets an interrupt.

                During the driver A interrupt handler, driver B gets an interrupt,
                this can happen since driver B interrupts are higher priority.

                Driver B calls mb_mapfree() which calls driver A's callback routine.
                Driver A didn't expect to be re-entered this way and something bad
                happens, such as a request list being damaged.

The observant will note that the bug above was fixed in SunOS 4.1
As I stated, we use 4.1.3. A chat with a Sun engineer over the phone
and a quick look at Sun's online databse pointed me to patch #100507-05.

Keywords: tmpfs crash fail assertion leaks anonymous tmp_rename panic spars files
Synopsis: SunOS 4.1.1, 4.1.2, 4.1.3: tmpfs jumbo patch

SunOS release: 4.1.1 4.1.2 4.1.3 4.1.3C

Topic: fixes for several tmpfs bugs

So I installed the patch. The guy who was running a large suimulation
when the system crashed ran his simulation again last night and everything
was OK


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