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Re: itrace patches


Dave Nomura <dcnltc@us.ibm.com> writes:

> Are the two patches that I submitted OK to commit?
> [...]

Thanks for committing.  I'll move the test suite file to the
appropriate place.  While testing that though, I found a problem, so
I'll initially disable the test.  Can you elaborate upon the level of
testing of this code?  Has it been run under lockdep?


On an RHEL5 x86-64 machine, I got:

BUG: soft lockup - CPU#0 stuck for 10s! [ls_15964:16126]
CPU 0:
Modules linked in: stap_7c70ff0a5aa33e45a459d750475957f4_763(U) xt_tcpudp iptable_nat ip_nat ip_conntrack nfnet
link ip_tables x_tables xfrm_nalgo crypto_api hidp l2cap bluetooth nfs lockd fscache nfs_acl sunrpc dm_multipat
h video sbs backlight i2c_ec button battery asus_acpi acpi_memhotplug ac lp floppy ata_piix libata scsi_mod i2c
_piix4 i2c_core pcspkr ide_cd 8139too parport_pc 8139cp mii parport serio_raw cdrom dm_snapshot dm_zero dm_mirr
or dm_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd
Pid: 16126, comm: ls_15964 Tainted: G      2.6.18-92.1.1.el5 #1
RIP: 0010:[<ffffffff80064b54>]  [<ffffffff80064b54>] .text.lock.spinlock+0x2/0x30
RSP: 0018:ffff81001d279dd0  EFLAGS: 00000286
RAX: 0000000000003efe RBX: ffff8100104b2900 RCX: 0000000000000000
RDX: ffff8100104b2900 RSI: ffff8100188ee860 RDI: ffffffff883f64c0
RBP: ffffffff80061e22 R08: ffff81001d278000 R09: 0000000000000001
R10: ffff810016f059c8 R11: 0000000300000000 R12: 0000000000000282
R13: a3754e699d64d231 R14: ffff81000563c000 R15: 0000000000003efe
FS:  0000000000000000(0000) GS:ffffffff8039f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007fff904eeaf9 CR3: 000000000dff2000 CR4: 00000000000006e0

Call Trace:
 [<ffffffff883e137f>] :stap_7c70ff0a5aa33e45a459d750475957f4_763:usr_itrace_init+0x92/0x17d
 [<ffffffff883e51e8>] :stap_7c70ff0a5aa33e45a459d750475957f4_763:__stp_utrace_attach_match_tsk+0x17c/0x22e
 [<ffffffff883e52e7>] :stap_7c70ff0a5aa33e45a459d750475957f4_763:__stp_utrace_task_finder_report_exec+0x4d/0x4f
 [<ffffffff800bd589>] utrace_report_exec+0x58/0x187
 [<ffffffff8003f49b>] search_binary_handler+0x171/0x26d
 [<ffffffff8003e950>] do_execve+0x18c/0x243
 [<ffffffff80054760>] sys_execve+0x36/0x4c


This could have been caused by create_itrace_info's use of an
uninitialized spin_lock.  It is not clear that a spinlock is
appropriate at all, considering which of the protected calls could
block.


- FChE


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