Come diagnosticare frequenti segfault

Il mio server sta registrando frequenti errori di segmentazione su /var/log/kern.log in diversi strumenti. Finora li ho visti in Perl, PHP e rsync. Tutto il software installato è pacchetti Debian aggiornati. Ecco un estratto dal file di registro:

Mar  2 01:07:54 gaz kernel: [ 5316.246303] imapsync[4533]: segfault at 8b ip 00007fb448c98fe6 sp 00007ffff571dd68 error 4 in libperl.so.5.10.1[7fb448bd7000+164000]
Mar  2 01:17:42 gaz kernel: [ 5904.354307] php5-cgi[4441]: segfault at 2bb3dc8 ip 0000000002bb3dc8 sp 00007fffbeeaae48 error 15
Mar  2 02:54:05 gaz kernel: [11687.922316] php5-cgi[4495]: segfault at 2d7acf9 ip 0000000002d7acf9 sp 00007fff60c6eb18 error 15
Mar  2 10:50:08 gaz kernel: [40250.390322] BUG: unable to handle kernel paging request at 00000000024b03f0
Mar  2 10:50:08 gaz kernel: [40250.390341] IP: [<00000000024b03f0>] 0x24b03f0
Mar  2 10:50:08 gaz kernel: [40250.390353] PGD 208c71067 PUD 21c811067 PMD 209329067 PTE 8000000211c88067
Mar  2 10:50:08 gaz kernel: [40250.390365] Oops: 0011 [#1] SMP 
Mar  2 10:50:08 gaz kernel: [40250.390373] last sysfs file: /sys/devices/pci0000:00/0000:00:12.0/host4/target4:0:0/4:0:0:0/block/sdb/stat
Mar  2 10:50:08 gaz kernel: [40250.390386] CPU 1 
Mar  2 10:50:08 gaz kernel: [40250.390392] Modules linked in: cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative xt_recent xt_tcpudp iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_
ipv4 ip6table_filter ip6_tables xt_DSCP xt_TCPMSS ipt_LOG ipt_REJECT iptable_mangle iptable_filter xt_multiport xt_state xt_limit xt_conntrack nf_conntrack_ftp nf_conntrack ip_tables x_tables loop snd
_hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_hwdep snd_pcm radeon snd_timer ttm snd drm_kms_helper soundcore drm snd_page_alloc i2c_algo_bit shpchp i2c_piix4 edac_core pcspkr k8temp evdev edac_m
ce_amd pci_hotplug i2c_core button ext3 jbd mbcache dm_mod powernow_k8 aacraid 3w_9xxx 3w_xxxx raid10 raid456 async_raid6_recov async_pq raid6_pq async_xor xor async_memcpy async_tx raid1 raid0 md_mod
 sata_nv sata_sil sata_via sd_mod crc_t10dif ata_generic ahci pata_atiixp ohci_hcd libata r8169 mii thermal ehci_hcd processor thermal_sys scsi_mod usbcore nls_base [last unloaded: scsi_wait_scan]
Mar  2 10:50:08 gaz kernel: [40250.390566] Pid: 11482, comm: munin-limits Not tainted 2.6.32-5-amd64 #1 MS-7368
Mar  2 10:50:08 gaz kernel: [40250.390576] RIP: 0010:[<00000000024b03f0>]  [<00000000024b03f0>] 0x24b03f0
Mar  2 10:50:08 gaz kernel: [40250.390586] RSP: 0018:ffff88021cc8dec0  EFLAGS: 00010286
Mar  2 10:50:08 gaz kernel: [40250.390593] RAX: 000000001ddc1000 RBX: 0000000000000010 RCX: ffffffff810f9904
Mar  2 10:50:08 gaz kernel: [40250.390600] RDX: 0000000000000000 RSI: ffffea0007688200 RDI: 0000000000000286
Mar  2 10:50:08 gaz kernel: [40250.390608] RBP: 00000000ffffffea R08: 0000000000000025 R09: 7865542f30312e35
Mar  2 10:50:08 gaz kernel: [40250.390615] R10: 000000d01cc8ddf8 R11: 0000000000000246 R12: ffff88021cc8def8
Mar  2 10:50:08 gaz kernel: [40250.390622] R13: 0000000002295010 R14: 00000000022c9db0 R15: 0000000002488d78
Mar  2 10:50:08 gaz kernel: [40250.390630] FS:  00007f3b3c8b2700(0000) GS:ffff880008d00000(0000) knlGS:0000000000000000
Mar  2 10:50:08 gaz kernel: [40250.390641] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar  2 10:50:08 gaz kernel: [40250.390648] CR2: 00000000024b03f0 CR3: 000000021c5d1000 CR4: 00000000000006e0
Mar  2 10:50:08 gaz kernel: [40250.390656] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Mar  2 10:50:08 gaz kernel: [40250.390663] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Mar  2 10:50:08 gaz kernel: [40250.390671] Process munin-limits (pid: 11482, threadinfo ffff88021cc8c000, task ffff88021bf59530)
Mar  2 10:50:08 gaz kernel: [40250.390681] Stack:
Mar  2 10:50:08 gaz kernel: [40250.390687]  ffffffff810f1d4a ffff880208c63228 0000000000000000 00007fffc2dcecc0
Mar  2 10:50:08 gaz kernel: [40250.390697] <0> 00000000024ba2b0 0000000002295010 ffffffff810f1e3d 0000000000000004
Mar  2 10:50:08 gaz kernel: [40250.390712] <0> ffff88021bf59530 ffff88021c4edc00 ffffffff812fe0b6 ffff88021c4edc60
Mar  2 10:50:08 gaz kernel: [40250.390732] Call Trace:
Mar  2 10:50:08 gaz kernel: [40250.390742]  [<ffffffff810f1d4a>] ? vfs_fstatat+0x2c/0x57
Mar  2 10:50:08 gaz kernel: [40250.390750]  [<ffffffff810f1e3d>] ? sys_newstat+0x11/0x30
Mar  2 10:50:08 gaz kernel: [40250.390760]  [<ffffffff812fe0b6>] ? do_page_fault+0x2e0/0x2fc
Mar  2 10:50:08 gaz kernel: [40250.390768]  [<ffffffff812fbf55>] ? page_fault+0x25/0x30
Mar  2 10:50:08 gaz kernel: [40250.390777]  [<ffffffff81010b42>] ? system_call_fastpath+0x16/0x1b
Mar  2 10:50:08 gaz kernel: [40250.390783] Code:  Bad RIP value.
Mar  2 10:50:08 gaz kernel: [40250.390791] RIP  [<00000000024b03f0>] 0x24b03f0
Mar  2 10:50:08 gaz kernel: [40250.390799]  RSP <ffff88021cc8dec0>
Mar  2 10:50:08 gaz kernel: [40250.390805] CR2: 00000000024b03f0
Mar  2 10:50:08 gaz kernel: [40250.391051] ---[ end trace 1cc1473b539c7f6e ]---
Mar  2 11:42:20 gaz kernel: [43382.242301] php5-cgi[10963]: segfault at d81160 ip 0000000000d81160 sp 00007fff3adcb058 error 15
Mar  2 21:51:14 gaz kernel: [79916.418302] php5-cgi[20089]: segfault at 1c59dc8 ip 0000000001c59dc8 sp 00007fff9b877fb8 error 15
Mar  3 03:45:01 gaz kernel: [101143.334305] munin-update[22519] general protection ip:7f516dce204c sp:7fff6049a978 error:0 in libperl.so.5.10.1[7f516dc7d000+164000]
Mar  3 11:22:37 gaz kernel: [128599.570307] php5-cgi[22888]: segfault at 36485a8 ip 00000000036485a8 sp 00007fff2d56e1c8 error 15
Mar  4 08:32:17 gaz kernel: [204779.842304] php5-cgi[22090]: segfault at 18 ip 0000000000689e5e sp 00007fff677a6a48 error 6 in php5-cgi[400000+6f9000]
Mar  4 10:01:02 gaz kernel: [210104.434706] rsync[22236] general protection ip:7f14a07137f9 sp:7fff88f940b8 error:0 in libc-2.11.2.so[7f14a069d000+158000]
Mar  4 11:32:22 gaz kernel: [215584.262316] BUG: unable to handle kernel paging request at 00000000ffffff9c
Mar  4 11:32:22 gaz kernel: [215584.262331] IP: [<00000000ffffff9c>] 0xffffff9c

Mar  4 11:32:22 gaz kernel: [215584.262343] PGD 0 
Mar  4 11:32:22 gaz kernel: [215584.262350] Oops: 0010 [#2] SMP 
Mar  4 11:32:22 gaz kernel: [215584.262359] last sysfs file: /sys/devices/pci0000:00/0000:00:12.0/host4/target4:0:0/4:0:0:0/block/sdb/stat
Mar  4 11:32:22 gaz kernel: [215584.262371] CPU 1 
Mar  4 11:32:22 gaz kernel: [215584.262378] Modules linked in: cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative xt_recent xt_tcpudp iptable_nat nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 ip6table_filter ip6_tables xt_DSCP xt_TCPMSS ipt_LOG ipt_REJECT iptable_mangle iptable_filter xt_multiport xt_state xt_limit xt_conntrack nf_conntrack_ftp nf_conntrack ip_tables x_tables loop snd_hda_codec_atihdmi snd_hda_intel snd_hda_codec snd_hwdep snd_pcm radeon snd_timer ttm snd drm_kms_helper soundcore drm snd_page_alloc i2c_algo_bit shpchp i2c_piix4 edac_core pcspkr k8temp evdev edac_mce_amd pci_hotplug i2c_core button ext3 jbd mbcache dm_mod powernow_k8 aacraid 3w_9xxx 3w_xxxx raid10 raid456 async_raid6_recov async_pq raid6_pq async_xor xor async_memcpy async_tx raid1 raid0 md_mod sata_nv sata_sil sata_via sd_mod crc_t10dif ata_generic ahci pata_atiixp ohci_hcd libata r8169 mii thermal ehci_hcd processor thermal_sys scsi_mod usbcore nls_base [last unloaded: scsi_wait_scan]
Mar  4 11:32:22 gaz kernel: [215584.262552] Pid: 1960, comm: proxymap Tainted: G      D    2.6.32-5-amd64 #1 MS-7368
Mar  4 11:32:22 gaz kernel: [215584.262563] RIP: 0010:[<00000000ffffff9c>]  [<00000000ffffff9c>] 0xffffff9c
Mar  4 11:32:22 gaz kernel: [215584.262573] RSP: 0018:ffff880209257e00  EFLAGS: 00010212
Mar  4 11:32:22 gaz kernel: [215584.262580] RAX: ffff8801514eb780 RBX: ffffffff810efb2d RCX: 0000000000000000
Mar  4 11:32:22 gaz kernel: [215584.262590] RDX: 0000000000000020 RSI: 0000000000000001 RDI: ffff8801514eb780
Mar  4 11:32:22 gaz kernel: [215584.262600] RBP: 00000000ffffffe9 R08: 0000000000000000 R09: 0000000000000000
Mar  4 11:32:22 gaz kernel: [215584.262611] R10: ffff880209257e78 R11: ffffffff81152c7c R12: 0000000000000001
Mar  4 11:32:22 gaz kernel: [215584.262622] R13: 0000000000008001 R14: 0000000000000024 R15: 00000000ffffff9c
Mar  4 11:32:22 gaz kernel: [215584.262633] FS:  00007fca4de35700(0000) GS:ffff880008d00000(0000) knlGS:0000000000000000
Mar  4 11:32:22 gaz kernel: [215584.262644] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Mar  4 11:32:22 gaz kernel: [215584.262650] CR2: 00000000ffffff9c CR3: 00000001c9cbb000 CR4: 00000000000006e0
Mar  4 11:32:22 gaz kernel: [215584.262661] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Mar  4 11:32:22 gaz kernel: [215584.262671] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Mar  4 11:32:22 gaz kernel: [215584.262682] Process proxymap (pid: 1960, threadinfo ffff880209256000, task ffff88021c4b1c40)
Mar  4 11:32:22 gaz kernel: [215584.262693] Stack:
Mar  4 11:32:22 gaz kernel: [215584.262698]  ffffffff810f8566 ffff880209257e78 ffff88021c7bf000 ffff88021c7bf0c8
Mar  4 11:32:22 gaz kernel: [215584.262709] <0> 0000800000000000 ffff88021fc0f000 ffff880209257e78 00000000fffffffe
Mar  4 11:32:22 gaz kernel: [215584.262724] <0> ffffffff810e5881 ffff880209257f48 0000000000000286 ffff88021fc0f000
Mar  4 11:32:22 gaz kernel: [215584.262743] Call Trace:
Mar  4 11:32:22 gaz kernel: [215584.262753]  [<ffffffff810f8566>] ? do_filp_open+0xa7/0x94b
Mar  4 11:32:22 gaz kernel: [215584.262763]  [<ffffffff810e5881>] ? virt_to_head_page+0x9/0x2a
Mar  4 11:32:22 gaz kernel: [215584.262771]  [<ffffffff810f9904>] ? user_path_at+0x52/0x79
Mar  4 11:32:22 gaz kernel: [215584.262779]  [<ffffffff810cfec1>] ? get_unmapped_area+0xd7/0x139
Mar  4 11:32:22 gaz kernel: [215584.262787]  [<ffffffff811019d5>] ? alloc_fd+0x67/0x10c
Mar  4 11:32:22 gaz kernel: [215584.262795]  [<ffffffff810eceaf>] ? do_sys_open+0x55/0xfc
Mar  4 11:32:22 gaz kernel: [215584.262804]  [<ffffffff81010b42>] ? system_call_fastpath+0x16/0x1b
Mar  4 11:32:22 gaz kernel: [215584.262811] Code:  Bad RIP value.
Mar  4 11:32:22 gaz kernel: [215584.262819] RIP  [<00000000ffffff9c>] 0xffffff9c
Mar  4 11:32:22 gaz kernel: [215584.262828]  RSP <ffff880209257e00>
Mar  4 11:32:22 gaz kernel: [215584.262833] CR2: 00000000ffffff9c
Mar  4 11:32:22 gaz kernel: [215584.263077] ---[ end trace 1cc1473b539c7f6f ]---

Come puoi vedere ci sono segfault, un errore di protezione generale e un kernel Oops. La mia prima ipotesi è stata che c'è un problema hardware di qualche tipo e ho chiesto al mio Hoster (è un server root noleggiato) di fare un completo controllo hardwar - lo hanno fatto, ma non sono riuscito a trovare alcun problema.

Non so cosa e come abbiano verificato, ma il loro team di supporto è generalmente abbastanza buono. Ho eseguito me stesso memtester e cpuburn e non sono riuscito a trovare alcun errore.

Sfortunatamente non ho un modo affidabile per riprodurre questi segfault, sembrano essere più o meno casuali. In un istante ho disabilitato il firewall del sistema ed eseguito uno dei programmi che segfault regolarmente (imapsync) e sembrava segfault impiegare più tempo di prima, quindi il problema potrebbe essere correlato allo stack di rete. O potrebbe essere solo una cosa a caso.

Ecco le specifiche del kernel:

# uname -a
Linux gaz 2.6.32-5-amd64 #1 SMP Wed Jan 12 03:40:32 UTC 2011 x86_64 GNU/Linux
# cat /etc/debian_version 
6.0
# lsmod
Module                  Size  Used by
cpufreq_userspace       1992  0 
cpufreq_stats           2659  0 
cpufreq_powersave        902  0 
cpufreq_conservative     5162  0 
xt_recent               5977  0 
xt_tcpudp               2319  0 
iptable_nat             4299  0 
nf_nat                 13388  1 iptable_nat
nf_conntrack_ipv4       9833  3 iptable_nat,nf_nat
nf_defrag_ipv4          1139  1 nf_conntrack_ipv4
ip6table_filter         2384  0 
ip6_tables             15075  1 ip6table_filter
xt_DSCP                 1995  0 
xt_TCPMSS               2919  0 
ipt_LOG                 4518  0 
ipt_REJECT              1953  0 
iptable_mangle          2817  0 
iptable_filter          2258  0 
xt_multiport            2267  0 
xt_state                1303  0 
xt_limit                1782  0 
xt_conntrack            2407  0 
nf_conntrack_ftp        5537  0 
nf_conntrack           46535  6 iptable_nat,nf_nat,nf_conntrack_ipv4,xt_state,xt_conntrack,nf_conntrack_ftp
ip_tables              13899  3 iptable_nat,iptable_mangle,iptable_filter
x_tables               12845  13 xt_recent,xt_tcpudp,iptable_nat,ip6_tables,xt_DSCP,xt_TCPMSS,ipt_LOG,ipt_REJECT,xt_multiport,xt_state,xt_limit,xt_conntrack,ip_tables
loop                   11799  0 
radeon                573996  0 
ttm                    39986  1 radeon
drm_kms_helper         20065  1 radeon
snd_hda_codec_atihdmi     2251  1 
drm                   142359  3 radeon,ttm,drm_kms_helper
snd_hda_intel          20019  0 
i2c_algo_bit            4225  1 radeon
pcspkr                  1699  0 
i2c_piix4               8328  0 
snd_hda_codec          54244  2 snd_hda_codec_atihdmi,snd_hda_intel
i2c_core               15712  5 radeon,drm_kms_helper,drm,i2c_algo_bit,i2c_piix4
snd_hwdep               5380  1 snd_hda_codec
snd_pcm                60503  2 snd_hda_intel,snd_hda_codec
snd_timer              15582  1 snd_pcm
snd                    46446  5 snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_timer
soundcore               4598  1 snd
evdev                   7352  3 
snd_page_alloc          6249  2 snd_hda_intel,snd_pcm
k8temp                  3283  0 
edac_core              29261  0 
edac_mce_amd            6433  0 
shpchp                 26264  0 
pci_hotplug            21203  1 shpchp
button                  4650  0 
ext3                  106518  2 
jbd                    37085  1 ext3
mbcache                 5050  1 ext3

dm_mod                 53754  0 
powernow_k8            10978  1 
aacraid                59779  0 
3w_9xxx                28684  0 
3w_xxxx                20569  0 
raid10                 17809  0 
raid456                44500  0 
async_raid6_recov       5170  1 raid456
async_pq                3479  2 raid456,async_raid6_recov
raid6_pq               77179  2 async_raid6_recov,async_pq
async_xor               2478  3 raid456,async_raid6_recov,async_pq
xor                     4380  1 async_xor
async_memcpy            1198  2 raid456,async_raid6_recov
async_tx                1734  5 raid456,async_raid6_recov,async_pq,async_xor,async_memcpy
raid1                  18431  3 
raid0                   5517  0 
md_mod                 73824  7 raid10,raid456,raid1,raid0
sata_nv                19166  0 
sata_sil                7412  0 
sata_via                7928  0 
sd_mod                 29889  8 
crc_t10dif              1276  1 sd_mod
ata_generic             3047  0 
ahci                   32374  6 
r8169                  29229  0 
mii                     3210  1 r8169
thermal                11674  0 
pata_atiixp             3489  0 
libata                133632  6 sata_nv,sata_sil,sata_via,ata_generic,ahci,pata_atiixp
ohci_hcd               19212  0 
ehci_hcd               31151  0 
processor              29935  1 powernow_k8
thermal_sys            11942  2 thermal,processor
scsi_mod              122149  5 aacraid,3w_9xxx,3w_xxxx,sd_mod,libata
usbcore               122034  3 ohci_hcd,ehci_hcd
nls_base                6377  1 usbcore
# free 
             total       used       free     shared    buffers     cached
Mem:       8166128    1228036    6938092          0     140412     782060
-/+ buffers/cache:     305564    7860564
Swap:      2102456          0    2102456

Quindi, sostanzialmente le mie domande sono:

1. Come posso diagnosticare ulteriormente?
2. Esistono dati nel registro sopra che potrebbero aiutarmi a isolare il piantagrane?
3. Ci sono problemi noti con l'hardware / software di cui sopra che ho ignorato quando cercavo su Google?
4. C'è un modo per impedire al kernel di caricare automaticamente i moduli (probabilmente non ho bisogno di tutti questi moduli e uno di questi potrebbe essere il colpevole)

Controlla la tua memoria!

La causa più frequente di segfault casuali come questo è la cattiva memoria. Prendi un controllo memoria (come memtest86 + ) e testalo .

Cose con cui iniziare ... Controlla quanta memoria ha il server. Controlla la dimensione della tua partizione di swap. Controlla altri file di registro per potenziali fonti di informazioni (syslog.) Controlla se ci sono problemi noti con la versione del kernel e il tuo attuale hardware (o sistema di virtualizzazione.) Sto eseguendo Debian 6 con questo kernel in un piccolo (vmware) vm, senza problemi.

Una cosa che vorrei verificare è se il tuo provider di hosting utilizza la cosiddetta "RAM burstable". È abbastanza comune per gli host a basso costo avere un po 'di RAM di base, che può essere temporaneamente espansa. Il problema con questa RAM temporaneamente espansa è che non puoi fare affidamento su di essa, poiché può essere rimosso a metà del calcolo, con conseguente segfault.