[FTRACE] Enabling function_graph causes OOPS

[Sachin Sant]

Steven Rostedt wrote:
> I'm going through old email, and I found this. Do you still see this
> error. I don't recall seeing it myself.
>   
I can still recreate this with 31-rc9. When i enable tracing
with function_graph i notice the following oops. This happens
only once. Later if i try to enable/disable tracing i don't
get this oops message. This behavior is observed only with
function_graph. Other tracers work fine.

Oops: Kernel access of bad area, sig: 11 [#1]
SMP NR_CPUS=1024 NUMA pSeries
Modules linked in: ipv6 fuse loop dm_mod sr_mod ehea ibmveth sg cdrom sd_mod crc_t10dif ibmvscsic scsi_transport_srp scsi_tgt scsi_mod
NIP: c000000000008f30 LR: c000000000008f04 CTR: 80000000000f6d68
REGS: c00000003e98f560 TRAP: 0300   Not tainted  (2.6.31-rc9)
MSR: 8000000000009032 <EE,ME,IR,DR>  CR: 24000422  XER: 00000020
DAR: 0000000000000008, DSISR: 0000000040000000
TASK = c00000003e953b20[2483] 'irqbalance' THREAD: c00000003e98c000 CPU: 1
GPR00: c000000000008f04 c00000003e98f7e0 d00000000117ed38 0000000000000000
GPR04: 0000000000000000 0000000066000000 00000000000010bf 0000000000000000
GPR08: 0000000000000000 800000010021bb40 00000000000000ff 800000010021bb60
GPR12: 0000000000000002 c000000001032800 0000000000000000 ffffffffeffdff68
GPR16: 00000fffa39fd6a0 00000fffa39e6c38 c00000003ebe9c38 fffffffffffff000
GPR20: c00000002a6cf980 c00000003e98fdf8 c00000003e98fba8 00000fffa1740000
GPR24: fffffffffffff000 8001000003000000 ffe0000000000000 0000000000000009
GPR28: c00000003db40000 0000000000020000 d00000000117da78 c00000003e98f850
NIP [c000000000008f30] .mod_return_to_handler+0x2c/0x64
LR [c000000000008f04] .mod_return_to_handler+0x0/0x64
Call Trace:
[c00000003e98f7e0] [c00000002a6cf980] 0xc00000002a6cf980 (unreliable)
[c00000003e98f850] [c000000000008f04] .mod_return_to_handler+0x0/0x64
[c00000003e98f900] [c000000000008f04] .mod_return_to_handler+0x0/0x64
[c00000003e98f9a0] [c000000000008f04] .mod_return_to_handler+0x0/0x64
[c00000003e98fa30] [c000000000008ed0] .return_to_handler+0x0/0x34 (.bad_page_fault+0xc8/0xe8)
[c00000003e98fb30] [c000000000008ed0] .return_to_handler+0x0/0x34 (handle_page_fault+0x3c/0x5c)
[c00000003e98fc20] [c000000000008ed0] .return_to_handler+0x0/0x34 (.ehea_h_query_ehea_port+0x74/0x9c [ehea])
[c00000003e98fcd0] [c000000000008ed0] .return_to_handler+0x0/0x34 (.ehea_get_stats+0xa0/0x1d0 [ehea])
[c00000003e98fd80] [c000000000008ed0] .return_to_handler+0x0/0x34 (.dev_get_stats+0x50/0xec)
[c00000003e98fe30] [c000000000008ed0] .return_to_handler+0x0/0x34 (.dev_seq_show+0x5c/0x140)
Instruction dump:
4e800020 f881ffe0 f861ffe8 f841fff0 fbe1fff8 7c3f0b78 f821ff91 3c800000
60840000 788407c6 64840000 60840000 <e8440008> 48126375 60000000 7c6803a6
---[ end trace bb43efc994aed790 ]---

function_graph traces are recorded and can be retrieved using
/sys/kernel/debug/tracing/trace.

1)   3.936 us    |                        }
1)               |                        .release_console_sem() {
1)   0.594 us    |                          ._spin_lock_irqsave();
1)   0.560 us    |                          ._call_console_drivers();
1)   0.580 us    |                          ._call_console_drivers();
1)   0.582 us    |                          ._spin_lock_irqsave();
1)               |                          .up() {
1)   0.592 us    |                            ._spin_lock_irqsave();
1)   0.556 us    |                            ._spin_unlock_irqrestore();
1)   2.842 us    |                          }
1)   0.588 us    |                          ._spin_unlock_irqrestore();
1)   9.750 us    |                        }
1) + 75.274 us   |                      }
1)               |                      .die() {
1)               |                        .oops_enter() {

Thanks
-Sachin

-- 

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Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India
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