SMP issues on ARM11 MPCore

[Russell King - ARM Linux]

I think you need to ask the authors of the module code / note code.

On Thu, Jan 07, 2010 at 02:45:11PM +0100, Dirk Behme wrote:
> On Thu, Jan 7, 2010 at 11:50 AM, Dirk Behme <dirk.behme at googlemail.com> wrote:
> > On Thu, Dec 24, 2009 at 4:27 PM, mkl lin <mkl0301 at hotmail.com> wrote:
> >>
> >> hi,
> >>
> >> I'm using ARM11 MPCore with 2 CPU, Linux-2.6.31.1, SMP enabled, L1 enabled, L2 disabled
> >>
> >> Under SMP environment, I have observed following issues:
> >>
> >> case 1
> >> Sometimes, console became extremely slow, print 1 character for 1-2 seconds
> >> RVDS say that both CPU are idling.  kernel seems find because messages  response to inserting USB flash is quick and correct.
> >>
> >> case 2
> >> Sometimes,  the Linux console halt and canot accept any input.
> >> RVDS say that both CPU are idling.  kernel seems fine because messages  response to inserting USB flash is quick and correct.
> >>
> >> case 3
> >> Sometimes, the test stop with no reason or some fault like segmantation fault and return to console prompt or login prompt.
> >>
> >> case 4
> >> Sometimes,
> >> the test stop with no reason, but not returning to console prompt. The
> >> console can accept input, but no further response, nor prompt.
> >>
> >> RVDS says that one CPU is idling, the other is in IRQ context, at
> >> entry-armv.S(676) after __pabt_usr, seems like it's keeps getting
> >> prefetch abort.
> >>
> >>
> >> I can duplicate case 1 by keep inserting a simple test module.
> >>
> >> -------
> >>
> >> #include <linux/init.h>
> >> #include <linux/module.h>
> >>
> >>
> >> static int __init MYDRIVER_init(void)
> >> {
> >>
> >> printk("%s: \n",__func__);
> >> return 0;
> >> }
> >>
> >> static void __exit MYDRIVER_exit(void)
> >> {
> >> printk("%s: \n",__func__);
> >> }
> >>
> >> MODULE_AUTHOR("Mac Lin");
> >> MODULE_DESCRIPTION("MYDRIVER");
> >> MODULE_LICENSE("GPL");
> >>
> >> module_init(MYDRIVER_init);
> >> module_exit(MYDRIVER_exit);
> >> -------
> >
> > We tested above simple module on a 4 CPU ARM11 MPCore system using
> > 2.6.32, too. Script to do this is very simple
> >
> >> cat test.sh
> > insmod module.ko
> > rmmod module.ko
> > insmod module.ko
> > ....
> >
> > This immediately results in [1]  (user_debug=31 enabled).
> >
> > Doing some further investigation, we found that [1] happens only if
> > module init and exit function are _both_ marked with __init/__exit.
> > Removing __init or __exit or both seems to make the test (~50 times)
> > run fine.
> >
> > Any further proposals for testing or debugging?
> >
> > Best regards
> >
> > Dirk
> >
> > [1] ~ # ./test.sh
> >  MYDRIVER_init
> >  MYDRIVER_exit
> >  Unable to handle kernel NULL pointer dereference at virtual address 00000000
> >  pgd = cc37c000
> >  [00000000] *pgd=8c38f031, *pte=00000000, *ppte=00000000
> >  Internal error: Oops: 17 [#1] SMP
> >  last sysfs file:
> >  Modules linked in: [last unloaded: module]
> >  CPU: 0    Not tainted  (2.6.32-00012-g89b993e-dirty #17)
> >  PC is at strcmp+0x8/0x34
> >  LR is at sysfs_find_dirent+0x18/0x38
> >  pc : [<c094bd8c>]    lr : [<c08ede4c>]    psr: a0000013
> >  sp : cc26bef8  ip : 00000000  fp : 00000000
> >  r10: 40025000  r9 : cc26a000  r8 : 00000880
> >  r7 : cc26bf44  r6 : 00000000  r5 : 00000000  r4 : cc326428
> >  r3 : 000009b3  r2 : 00000000  r1 : 00000000  r0 : 00000000
> >  Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
> >  Control: 08c5787d  Table: 8c37c00a  DAC: 00000015
> >  Process rmmod (pid: 378, stack limit = 0xcc26a270)
> >  Stack: (0xcc26bef8 to 0xcc26c000)
> >  bee0:                                                       cc3263f8 00000000
> >  bf00: 00000000 c08ec918 cc3263f8 00000000 00000000 00000000 00000000 ccd961e0
> >  bf20: 00000000 c087de50 bf000074 bf000074 00000000 c087e214 00000000 c087e550
> >  bf40: 00000001 75646f6d cc00656c cc37d000 cc25ba20 cc25ba64 cc25ba54 00000000
> >  bf60: 40025000 00000000 40025000 00000001 cc26a000 4002501c bef869c4 0089e8e8
> >  bf80: bf000074 00000880 cc26bf8c 00000000 be00656c 400256c0 00000000 00000081
> >  bfa0: c0842224 c08420a0 be00656c 400256c0 bef86b80 00000880 00000000 75646f6d
> >  bfc0: be00656c 400256c0 00000000 00000081 00000059 00000000 40025000 00000000
> >  bfe0: bef86b80 bef86b70 00012fe0 400e7740 60000010 bef86b80 00000000 00000000
> >  [<c094bd8c>] (strcmp+0x8/0x34) from [<c08ede4c>] (sysfs_find_dirent+0x18/0x38)
> >  [<c08ede4c>] (sysfs_find_dirent+0x18/0x38) from [<c08ec918>]
> > (sysfs_hash_and_remove+0x28/0x60)
> >  [<c08ec918>] (sysfs_hash_and_remove+0x28/0x60) from [<c087de50>]
> > (free_notes_attrs+0x2c/0x4c)
> >  [<c087de50>] (free_notes_attrs+0x2c/0x4c) from [<c087e214>]
> > (free_module+0x2c/0xdc)
> >  [<c087e214>] (free_module+0x2c/0xdc) from [<c087e550>]
> > (sys_delete_module+0x214/0x250)
> >  [<c087e550>] (sys_delete_module+0x214/0x250) from [<c08420a0>]
> > (ret_fast_syscall+0x0/0x2c)
> 
> Debugging of above call stack shows:
> 
> strcmp() fails due to both parameters, cs and ct being NULL.
> 
> Function free_module() gets 'struct module *mod' as parameter. This
> has an element
> 
> mod->notes_attrs->attrs[0].attr.name
> 
> In case of module's init and exit function are _both_ marked with
> __init/__exit, this name is NULL. This is then parsed down by above
> call stack and let strcmp() fail.
> 
> In case init and/or exit function in above module don't have
> __init/__exit, name is a valid pointer.
> 
> Any idea what might cause this?
> 
> Many thanks and best regards
> 
> Dirk
> 
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