Duplicate free

[Arne Wörner]

How do u do that?
Any special test program?

Does it happen in R6.2 and/or 7-CUR, too?

R there any exceptional events shortly before it happens?

-Arne


--- David Cecil <david.cecil at nokia.com> wrote:

> A little more information that I hope might trigger some thoughts.
> 
> I have also seen a trace very similar to the one in my original mail, 
> but instead of bio_done calling g_disk_done, it calls g_mirror_done.  
> This time it panics because it tries to dereference the bio_from field.  
> The common thread is that in both cases, the bio is freed prior to the 
> done handler referencing it (well at least the bio_from field is NULL in 
> the g_mirror_case, so I'm assuming it was freed).  I wonder if these 
> handlers are not playing nicely together?  Some locking required between 
> them that is missing maybe?
> 
> 
> Unread portion of the kernel message buffer:
> ad4: TIMEOUT - WRITE_DMA retrying (1 retry left) LBA=46231338
> 
> Fatal trap 12: page fault while in kernel mode
> cpuid = 1; apic id = 01
> fault virtual address   = 0x0
> fault code              = supervisor read, page not present
> instruction pointer     = 0x20:0x8053318b
> stack pointer           = 0x28:0xe1466c4c
> frame pointer           = 0x28:0xe1466c54
> code segment            = base 0x0, limit 0xfffff, type 0x1b
>                         = DPL 0, pres 1, def32 1, gran 1
> processor eflags        = interrupt enabled, resume, IOPL = 0
> current process         = 19 (swi6: task queue)
> trap number             = 12
> panic: page fault
> cpuid = 1
> KDB: stack backtrace:
> db_trace_self_wrapper(8075f7be) at db_trace_self_wrapper+0x25
> kdb_backtrace(100,863ba190,28,e1466c0c,c,...) at kdb_backtrace+0x29
> panic(807403d4,8077f4a5,0,fffff,863be29b,...) at panic+0x124
> trap_fatal(e1466c0c,0,863ba190,0,c,...) at trap_fatal+0x2ce
> trap_pfault(e1466c0c,0,0) at trap_pfault+0x1e7
> trap(e1460008,28,28,8a0cb840,89b1a6b4,...) at trap+0x36d
> calltrap() at calltrap+0x5
> --- trap 0xc, eip = 0x8053318b, esp = 0xe1466c4c, ebp = 0xe1466c54 ---
> g_mirror_done(89b1a6b4) at g_mirror_done+0xb
> biodone(89b1a6b4) at biodone+0x8b
> ad_done(8a0cb840) at ad_done+0x2a
> ata_completed(8a0cb840,0) at ata_completed+0x534
> taskqueue_run(8644bac0,e1466cec,80566279,0,0,...) at taskqueue_run+0xbd
> taskqueue_swi_run(0) at taskqueue_swi_run+0xe
> ithread_execute_handlers(863be200,86433000) at 
> ithread_execute_handlers+0x139
> ithread_loop(86468460,e1466d38) at ithread_loop+0x64
> fork_exit(805662ec,86468460,e1466d38) at fork_exit+0x71
> fork_trampoline() at fork_trampoline+0x8
> --- trap 0x1, eip = 0, esp = 0xe1466d6c, ebp = 0 ---
> 
> 
> 
> ext David Cecil wrote:
> > Hi,
> >
> > I've encountered a duplicate free in 6.1-RELEASE-based code.  I have 
> > noticed that the same stack trace was reported about two years ago on 
> > a number of occasions, and some code was added to try and help debug 
> > the situation.  However, I don't see any resolution.  Does anyone have 
> > any more information on this before I try and debug it further?
> >
> > Any hints for trying to find who freed it first?  Maybe I should add 
> > the KTR debug that went into 1.66 of geom_io.c.
> >
> > db> bt
> > Tracing pid 17 tid 100016 td 0x86badaf0
> > kdb_enter(80750631) at kdb_enter+0x2b
> > panic(807786cd,8a778d80,81856780,80747d25,807786b1,...) at panic+0x137
> > uma_dbg_free(81856780,0,8a778d80) at uma_dbg_free+0x110
> > uma_zfree_arg(81856780,8a778d80,0) at uma_zfree_arg+0x66
> > g_destroy_bio(8a778d80,805319b4,8a778d80,e1ca3c60,805c9620,...) at 
> > g_destroy_bio+0x13
> > g_disk_done(8a778d80) at g_disk_done+0x62
> > biodone(8a778d80) at biodone+0x58
> > ad_done(88042840) at ad_done+0x2a
> > ata_completed(88042840,0,86c38cdc,0,80753b6d,...) at ata_completed+0x504
> > taskqueue_run(86c38cc0,e1ca3cec,8056999a,0,0,...) at taskqueue_run+0x86
> > taskqueue_swi_run(0) at taskqueue_swi_run+0xe
> > ithread_execute_handlers(86c14000,86c29280) at 
> > ithread_execute_handlers+0xfa
> > ithread_loop(86c534f0,e1ca3d38,86c534f0,80569a10,0,...) at 
> > ithread_loop+0x76
> > fork_exit(80569a10,86c534f0,e1ca3d38) at fork_exit+0xa0
> > fork_trampoline() at fork_trampoline+0x8
> > --- trap 0x1, eip = 0, esp = 0xe1ca3d6c, ebp = 0 ---
> >
> > The panic string is:
> > Duplicate free of item 0x8a778d80 from zone 0x81856780(g_bio)
> >
> > Thanks,
> > Dave
> > _______________________________________________
> > freebsd-geom at freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-geom
> > To unsubscribe, send any mail to "freebsd-geom-unsubscribe at freebsd.org"
> 
> 
> -- 
> Software Engineer
> Secure and Mobile Connectivity
> Enterprise Solutions
> Nokia
> +61 7 5553 8307 (office)
> +61 412 728 222 (cell)
> 
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