Date: Tue, 12 Sep 2000 23:39:51 +0200 From: Bernd Walter <ticso@cicely5.cicely.de> To: Doug Rabson <dfr@nlsystems.com> Cc: John Baldwin <jhb@pike.osd.bsdi.com>, alpha@FreeBSD.ORG Subject: Re: Mutex's aren't recursing Message-ID: <20000912233951.A56554@cicely5.cicely.de> In-Reply-To: <Pine.BSF.4.21.0009122128540.86297-100000@salmon.nlsystems.com>; from dfr@nlsystems.com on Tue, Sep 12, 2000 at 09:32:23PM %2B0100 References: <200009120028.RAA71076@pike.osd.bsdi.com> <Pine.BSF.4.21.0009122128540.86297-100000@salmon.nlsystems.com>
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On Tue, Sep 12, 2000 at 09:32:23PM +0100, Doug Rabson wrote:
> I sent you some mail yesterday about this. I got the constraints wrong for
> the inline assembler in atomic_cmpset. I disassembled some of the code in
> interrupt.c which is trying to enter the mutex. You can clearly see that
> it is misusing t1 as both an input and output to the inline.
>
> 0xfffffc00005542c4 <interrupt+900>: lda t1,8(zero)
> 0xfffffc00005542c8 <interrupt+904>: ldq t0,64(t7)
> 0xfffffc00005542cc <interrupt+908>: ldq_l t1,0(s1)
> 0xfffffc00005542d0 <interrupt+912>: cmpeq t1,t1,t2
> 0xfffffc00005542d4 <interrupt+916>: beq t2,0xfffffc00005542e4 <interrupt+932>
> 0xfffffc00005542d8 <interrupt+920>: mov t0,t1
> 0xfffffc00005542dc <interrupt+924>: stq_c t1,0(s1)
>
> I'm just about to start testing this patch which should fix the problem
> and also provides efficent forms for
> atomic_{add,subtract,set,clear}_{32,64}. I also fixed the interrupt
> problems with the spin locks (I think).
Your patch does the following on a PC164 to me:
1. The mutex change will hang my system every second boot during PCI device
printings.
2. Both changes panic the system on boot:
[...]
da12: <IBM WDS-3200 !J S550> Fixed Direct Access SCSI-2 device
da12: 5.000MB/s transfers (5.000MHz, offset 7)
da12: 206MB (422912 512 byte sectors: 64H 32S/T 206C)
da14 at sym2 bus 0 target 3 lun 0
da14: <CDC 94221-5 5342> Fixed Direct Access SCSI-CCS device
da14: 3.300MB/s transfers
da14: 170MB (349770 512 byte sectors: 64H 32S/T 170C)
Mounting root from ufs:/dev/da0a
fatal kernel trap:
trap entry = 0x2 (memory management fault)
a0 = 0x0
a1 = 0x1
a2 = 0x0
pc = 0xfffffc0000517458
ra = 0xfffffc0000518fbc
curproc = 0xfffffe0008e02720
pid = 7, comm = init
Stopped at mtx_exit_hard+0x118: ldq t1,0(s1) <0x0> <t1=0x8,s1=0x0>
db> trace
mtx_exit_hard() at mtx_exit_hard+0x118
child_return() at child_return+0x9c
exception_return() at exception_return
--
B.Walter COSMO-Project http://www.cosmo-project.de
ticso@cicely.de Usergroup info@cosmo-project.de
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