[Bug runtime/10651] New: very rare BUG_ON kernel/timer.c:619 due to runtime/time.c

["fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

Something is calling mod_timer with a timer->function==NULL.

It appears as if the _stp_kill_time function is needlessly racy
(amongst the stp_timer_reregister flag, which should probably be
an atomic_t), and the del_timer_sync()'s.  It wouldn't hurt to
plop a synchronize_sched() in there too before the free_percpu
goo.

This was on an i686 rawhide 4cpu VM, 2.6.31-12.fc12.i686 kernel,
according to the systemtap.log, last attempted tes was bz5274.exp,
and here's the BUG message itself:

------------[ cut here ]------------
kernel BUG at kernel/timer.c:619!
invalid opcode: 0000 [#2] SMP 
last sysfs file: /sys/module/virtio_pci/sections/__mcount_loc
Modules linked in: stap_d91e5e64f72dff7c4c94d049e84aaaab_10830 uprobes
netconsole iptable_nat nf_nat nfsd exportfs configfs nfs lockd fscache nfs_acl
auth_rpcgss sunrpc ipv6 dm_multipath uinput ppdev parport_pc parport
virtio_balloon 8139too 8139cp mii i2c_piix4 i2c_core floppy virtio_pci [last
unloaded: stap_f28f0139d183e5474e8c3292a39d7c78_2115]

Pid: 10, comm: ksoftirqd/2 Tainted: G      D W  (2.6.31-12.fc12.i686 #1) 
EIP: 0060:[<c04503fc>] EFLAGS: 00010246 CPU: 2
EIP is at __mod_timer+0x35/0x110
EAX: 00000000 EBX: c3909f7c ECX: 00000000 EDX: 00000000
ESI: c3909f40 EDI: 00001ecc EBP: f6cdde8c ESP: f6cdde6c
 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Process ksoftirqd/2 (pid: 10, ti=f6cdc000 task=f6ce0000 task.ti=f6cdc000)
Stack:
 00000000 00bdafbe c0605a00 42ad3970 42ad3970 00000246 c3909f40 00001ecc
<0> f6cdde9c c0450547 00000000 42ad3970 f6cdded8 f7d8c15b 9e2aa125 11641494
<0> 00000000 c04500d6 33171125 00000000 2e380e90 4ab18a28 33171125 42ad3970
Call Trace:
 [<c0605a00>] ? spin_bug+0x33/0xae
 [<c0450547>] ? mod_timer+0x2c/0x44
 [<f7d8c15b>] ? __stp_time_timer_callback+0xd4/0xed
[stap_d91e5e64f72dff7c4c94d049e84aaaab_10830]
 [<c04500d6>] ? run_timer_softirq+0x133/0x204
 [<c0450121>] ? run_timer_softirq+0x17e/0x204
 [<c04500d6>] ? run_timer_softirq+0x133/0x204
 [<f7d8c087>] ? __stp_time_timer_callback+0x0/0xed
[stap_d91e5e64f72dff7c4c94d049e84aaaab_10830]
 [<c044b4f5>] ? __do_softirq+0xc8/0x192
 [<c044b63e>] ? ksoftirqd+0x0/0xd6
 [<c044b608>] ? do_softirq+0x49/0x7f
 [<c044b696>] ? ksoftirqd+0x58/0xd6
 [<c045cef1>] ? kthread+0x7b/0x80
 [<c045ce76>] ? kthread+0x0/0x80
 [<c040463f>] ? kernel_thread_helper+0x7/0x10
Code: 1f 44 00 00 89 c3 8b 45 08 89 55 e4 88 4d e8 65 8b 15 14 00 00 00 89 55 f0
31 d2 89 45 e0 89 d8 e8 05 ff ff ff 83 7b 0c 00 75 04 <0f> 0b eb fe 8d 55 ec 89
d8 e8 59 ff ff ff 83 3b 00 89 c6 74 10 
EIP: [<c04503fc>] __mod_timer+0x35/0x110 SS:ESP 0068:f6cdde6c
---[ end trace 8eed33dc7b203ed4 ]---

-- 
           Summary: very rare BUG_ON kernel/timer.c:619 due to
                    runtime/time.c
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: runtime
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10651

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