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[97.115.119.26]) by smtp.gmail.com with ESMTPSA id q132sm19902456pfq.16.2019.10.14.15.26.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Oct 2019 15:26:21 -0700 (PDT) Subject: Re: [PATCH net-next v2 00/10] optimize openvswitch flow looking up To: Tonghao Zhang Cc: Pravin Shelar , Linux Kernel Network Developers References: <1570496438-15460-1-git-send-email-xiangxia.m.yue@gmail.com> From: Gregory Rose Message-ID: Date: Mon, 14 Oct 2019 15:26:19 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 10/10/2019 1:42 AM, Tonghao Zhang wrote: > On Wed, Oct 9, 2019 at 1:33 AM Gregory Rose wrote: >> [snip] >> Hi Tonghao, >> >> I've applied your patch series and built a 5.4.0-rc1 kernel with them. >> >> xxxxx@ubuntu-1604:~$ modinfo openvswitch >> filename: /lib/modules/5.4.0-rc1+/kernel/net/openvswitch/openvswitch.ko >> alias: net-pf-16-proto-16-family-ovs_ct_limit >> alias: net-pf-16-proto-16-family-ovs_meter >> alias: net-pf-16-proto-16-family-ovs_packet >> alias: net-pf-16-proto-16-family-ovs_flow >> alias: net-pf-16-proto-16-family-ovs_vport >> alias: net-pf-16-proto-16-family-ovs_datapath >> license: GPL >> description: Open vSwitch switching datapath >> srcversion: F15EB8B4460D81BAA16216B >> depends: nf_conntrack,nf_nat,nf_conncount,libcrc32c,nf_defrag_ipv6,nsh >> retpoline: Y >> intree: Y >> name: openvswitch >> vermagic: 5.4.0-rc1+ SMP mod_unload modversions >> >> I then built openvswitch master branch from github and ran 'make >> check-kernel'. >> >> In doing so I ran into the following splat in this test: >> 63: conntrack - IPv6 fragmentation + vlan >> >> Here is the splat: >> [ 480.024215] ------------[ cut here ]------------ >> [ 480.024218] kernel BUG at net/openvswitch/flow_table.c:725! >> [ 480.024267] invalid opcode: 0000 [#1] SMP PTI >> [ 480.024297] CPU: 2 PID: 15717 Comm: ovs-vswitchd Tainted: G E >> 5.4.0-rc1+ #131 >> [ 480.024345] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 >> [ 480.024386] RIP: 0010:ovs_flow_tbl_remove+0x151/0x160 [openvswitch] >> [ 480.024424] Code: 55 f7 ea 89 f0 c1 f8 1f 29 c2 39 53 10 0f 8f 6a ff >> ff ff 48 89 ef d1 fe 5b 5d e9 8a ed ff ff 0f 0b 0f 0b b8 18 00 00 00 eb >> 92 <0f> 0b 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 >> [ 480.024527] RSP: 0018:ffffaf32c05e38c8 EFLAGS: 00010246 >> [ 480.024560] RAX: 0000000000000010 RBX: ffff9e4f6cd5a000 RCX: >> ffff9e4f6c585000 >> [ 480.024601] RDX: ffff9e4f6cd5a098 RSI: 0000000000000010 RDI: >> ffff9e4f6b2c6d20 >> [ 480.024642] RBP: ffffaf32c05e3b70 R08: ffff9e4f6c1651c0 R09: >> ffff9e4f756a43c0 >> [ 480.024684] R10: 0000000000000000 R11: ffffffffc06e5500 R12: >> ffff9e4f6baf7800 >> [ 480.024742] R13: ffff9e4f6b2c6d20 R14: ffff9e4f724a4e14 R15: >> 0000000000000007 >> [ 480.024790] FS: 00007fdd76058980(0000) GS:ffff9e4f77b00000(0000) >> knlGS:0000000000000000 >> [ 480.024836] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 480.024871] CR2: 00007ffd18a5ac60 CR3: 0000000230f3a002 CR4: >> 00000000001606e0 >> [ 480.024917] Call Trace: >> [ 480.024941] action_fifos_exit+0x3240/0x37b0 [openvswitch] >> [ 480.024979] ? __switch_to_asm+0x40/0x70 >> [ 480.025005] ? __switch_to_asm+0x34/0x70 >> [ 480.025031] ? __switch_to_asm+0x40/0x70 >> [ 480.025056] ? __switch_to_asm+0x40/0x70 >> [ 480.025082] ? __switch_to_asm+0x34/0x70 >> [ 480.025108] ? __switch_to_asm+0x40/0x70 >> [ 480.025134] ? __switch_to_asm+0x34/0x70 >> [ 480.025159] ? __switch_to_asm+0x40/0x70 >> [ 480.025185] ? __switch_to_asm+0x34/0x70 >> [ 480.025210] ? __switch_to_asm+0x40/0x70 >> [ 480.025236] ? __switch_to_asm+0x34/0x70 >> [ 480.025262] ? __switch_to_asm+0x40/0x70 >> [ 480.025287] ? __switch_to_asm+0x34/0x70 >> [ 480.025312] ? __switch_to_asm+0x40/0x70 >> [ 480.025338] ? __switch_to_asm+0x34/0x70 >> [ 480.025364] ? __switch_to_asm+0x40/0x70 >> [ 480.025389] ? __switch_to_asm+0x34/0x70 >> [ 480.025415] ? __switch_to_asm+0x40/0x70 >> [ 480.025443] ? __update_load_avg_se+0x11c/0x2e0 >> [ 480.025472] ? __update_load_avg_se+0x11c/0x2e0 >> [ 480.025503] ? update_load_avg+0x7e/0x600 >> [ 480.025529] ? update_load_avg+0x7e/0x600 >> [ 480.025556] ? update_curr+0x85/0x1d0 >> [ 480.025582] ? cred_has_capability+0x85/0x130 >> [ 480.025611] ? __nla_validate_parse+0x57/0x8a0 >> [ 480.025640] ? _cond_resched+0x15/0x40 >> [ 480.025666] ? genl_family_rcv_msg_attrs_parse.isra.14+0x93/0x100 >> [ 480.026523] genl_rcv_msg+0x1d9/0x490 >> [ 480.027385] ? __switch_to_asm+0x34/0x70 >> [ 480.028230] ? __switch_to_asm+0x40/0x70 >> [ 480.029050] ? __switch_to_asm+0x40/0x70 >> [ 480.029874] ? genl_family_rcv_msg_attrs_parse.isra.14+0x100/0x100 >> [ 480.030673] netlink_rcv_skb+0x4a/0x110 >> [ 480.031465] genl_rcv+0x24/0x40 >> [ 480.032312] netlink_unicast+0x1a0/0x250 >> [ 480.033059] netlink_sendmsg+0x2b4/0x3b0 >> [ 480.033758] sock_sendmsg+0x5b/0x60 >> [ 480.034422] ___sys_sendmsg+0x278/0x2f0 >> [ 480.035083] ? file_update_time+0x60/0x130 >> [ 480.035680] ? pipe_write+0x286/0x400 >> [ 480.036290] ? new_sync_write+0x12d/0x1d0 >> [ 480.036882] ? __sys_sendmsg+0x5e/0xa0 >> [ 480.037452] __sys_sendmsg+0x5e/0xa0 >> [ 480.038013] do_syscall_64+0x52/0x1a0 >> [ 480.038546] entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> [ 480.039083] RIP: 0033:0x7fdd7537fa6d >> [ 480.039596] Code: b9 20 00 00 75 10 b8 2e 00 00 00 0f 05 48 3d 01 f0 >> ff ff 73 31 c3 48 83 ec 08 e8 fe f6 ff ff 48 89 04 24 b8 2e 00 00 00 0f >> 05 <48> 8b 3c 24 48 89 c2 e8 47 f7 ff ff 48 89 d0 48 83 c4 08 48 3d 01 >> [ 480.040769] RSP: 002b:00007ffd18a6ad40 EFLAGS: 00000293 ORIG_RAX: >> 000000000000002e >> [ 480.041391] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: >> 00007fdd7537fa6d >> [ 480.042045] RDX: 0000000000000000 RSI: 00007ffd18a6ada0 RDI: >> 0000000000000014 >> [ 480.042713] RBP: 0000000002300870 R08: 0000000000000000 R09: >> 00007ffd18a6bd58 >> [ 480.043438] R10: 0000000000000000 R11: 0000000000000293 R12: >> 00007ffd18a6bb70 >> [ 480.044138] R13: 00007ffd18a6bd00 R14: 00007ffd18a6bb78 R15: >> 00007ffd18a6b230 >> [ 480.044852] Modules linked in: vport_vxlan(E) vxlan(E) vport_gre(E) >> ip_gre(E) ip_tunnel(E) vport_geneve(E) geneve(E) ip6_udp_tunnel(E) >> udp_tunnel(E) openvswitch(E) nsh(E) nf_conncount(E) nf_nat_tftp(E) >> nf_conntrack_tftp(E) nf_nat_ftp(E) nf_conntrack_ftp(E) nf_nat(E) >> nf_conntrack_netlink(E) ip6table_filter(E) ip6_tables(E) >> iptable_filter(E) ip_tables(E) x_tables(E) ip6_gre(E) ip6_tunnel(E) >> tunnel6(E) gre(E) bonding(E) 8021q(E) garp(E) stp(E) mrp(E) llc(E) >> veth(E) nfnetlink_cttimeout(E) nfnetlink(E) nf_conntrack(E) >> nf_defrag_ipv6(E) nf_defrag_ipv4(E) binfmt_misc(E) intel_rapl_msr(E) >> snd_hda_codec_generic(E) ledtrig_audio(E) snd_hda_intel(E) >> snd_intel_nhlt(E) joydev(E) snd_hda_codec(E) input_leds(E) >> snd_hda_core(E) snd_hwdep(E) intel_rapl_common(E) snd_pcm(E) >> snd_timer(E) serio_raw(E) snd(E) soundcore(E) i2c_piix4(E) mac_hid(E) >> ib_iser(E) rdma_cm(E) iw_cm(E) ib_cm(E) ib_core(E) configfs(E) >> iscsi_tcp(E) libiscsi_tcp(E) libiscsi(E) scsi_transport_iscsi(E) >> autofs4(E) btrfs(E) zstd_decompress(E) >> [ 480.044888] zstd_compress(E) raid10(E) raid456(E) >> async_raid6_recov(E) async_memcpy(E) async_pq(E) async_xor(E) >> async_tx(E) xor(E) raid6_pq(E) libcrc32c(E) raid1(E) raid0(E) >> multipath(E) linear(E) crct10dif_pclmul(E) crc32_pclmul(E) >> ghash_clmulni_intel(E) aesni_intel(E) qxl(E) crypto_simd(E) ttm(E) >> cryptd(E) glue_helper(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) >> sysimgblt(E) fb_sys_fops(E) psmouse(E) drm(E) floppy(E) pata_acpi(E) >> [last unloaded: nf_conntrack_ftp] >> [ 480.056765] ---[ end trace 4a8c4eceeb9f5dec ]--- >> [ 480.057953] RIP: 0010:ovs_flow_tbl_remove+0x151/0x160 [openvswitch] >> [ 480.059134] Code: 55 f7 ea 89 f0 c1 f8 1f 29 c2 39 53 10 0f 8f 6a ff >> ff ff 48 89 ef d1 fe 5b 5d e9 8a ed ff ff 0f 0b 0f 0b b8 18 00 00 00 eb >> 92 <0f> 0b 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 >> [ 480.061623] RSP: 0018:ffffaf32c05e38c8 EFLAGS: 00010246 >> [ 480.062959] RAX: 0000000000000010 RBX: ffff9e4f6cd5a000 RCX: >> ffff9e4f6c585000 >> [ 480.064248] RDX: ffff9e4f6cd5a098 RSI: 0000000000000010 RDI: >> ffff9e4f6b2c6d20 >> [ 480.065524] RBP: ffffaf32c05e3b70 R08: ffff9e4f6c1651c0 R09: >> ffff9e4f756a43c0 >> [ 480.066830] R10: 0000000000000000 R11: ffffffffc06e5500 R12: >> ffff9e4f6baf7800 >> [ 480.068870] R13: ffff9e4f6b2c6d20 R14: ffff9e4f724a4e14 R15: >> 0000000000000007 >> [ 480.070081] FS: 00007fdd76058980(0000) GS:ffff9e4f77b00000(0000) >> knlGS:0000000000000000 >> [ 480.071340] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 480.072610] CR2: 00007ffd18a5ac60 CR3: 0000000230f3a002 CR4: >> 00000000001606e0 >> >> You're hitting the BUG_ON here: >> >> /* Must be called with OVS mutex held. */ >> void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow) >> { >> struct table_instance *ti = ovsl_dereference(table->ti); >> struct table_instance *ufid_ti = ovsl_dereference(table->ufid_ti); >> >> BUG_ON(table->count == 0); >> <------------------------------------------------ Here > Hi Greg, > Thanks for your work, I fixed it, when relloac mask_array I don't > update ma point in patch 5. > > diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c > index bc14b12..210018a 100644 > --- a/net/openvswitch/flow_table.c > +++ b/net/openvswitch/flow_table.c > @@ -827,6 +827,8 @@ static int tbl_mask_array_add_mask(struct flow_table *tbl, > MASK_ARRAY_SIZE_MIN); > if (err) > return err; > + > + ma = ovsl_dereference(tbl->mask_array); > } > > BUG_ON(ovsl_dereference(ma->masks[ma->count])); Hi Tonghao, I did make the change you suggested: git diff diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index bc14b12..210018a 100644 --- a/net/openvswitch/flow_table.c +++ b/net/openvswitch/flow_table.c @@ -827,6 +827,8 @@ static int tbl_mask_array_add_mask(struct flow_table *tbl,                                               MASK_ARRAY_SIZE_MIN);                 if (err)                         return err; + +               ma = ovsl_dereference(tbl->mask_array);         } However, there is still an issue.  Apparently this change just moves the bug.  Now I'm getting this splat: [  512.147478] ------------[ cut here ]------------ [  512.147481] kernel BUG at net/openvswitch/flow_table.c:725! [  512.147526] invalid opcode: 0000 [#1] SMP PTI [  512.147552] CPU: 1 PID: 14636 Comm: ovs-vswitchd Tainted: G            E     5.4.0-rc1+ #138 [  512.147595] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [  512.147630] RIP: 0010:ovs_flow_tbl_remove+0x151/0x160 [openvswitch] [  512.147663] Code: 55 f7 ea 89 f0 c1 f8 1f 29 c2 39 53 10 0f 8f 6a ff ff ff 48 89 ef d1 fe 5b 5d e9 8a ed ff ff 0f 0b 0f 0b b8 18 00 00 00 eb 92 <0f> 0b 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 [  512.147753] RSP: 0018:ffffb637002cf8c8 EFLAGS: 00010246 [  512.147781] RAX: 0000000000000009 RBX: ffff95ebf32d23c0 RCX: ffff95ebf00e5a00 [  512.147817] RDX: ffff95ebf32d2420 RSI: 0000000000000009 RDI: ffff95ebf0dffba0 [  512.147852] RBP: ffffb637002cfb70 R08: ffff95ebf6030240 R09: ffff95ebf1643180 [  512.147888] R10: ffff95ebf283b814 R11: ffffffffc0932500 R12: ffff95ebf040a300 [  512.147924] R13: ffff95ebf0dffba0 R14: ffff95ebf283b814 R15: 0000000000000007 [  512.147961] FS:  00007fbbab3d2980(0000) GS:ffff95ebf7a80000(0000) knlGS:0000000000000000 [  512.148001] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [  512.148031] CR2: 00007fffca190ff8 CR3: 0000000232810006 CR4: 00000000001606e0 [  512.148071] Call Trace: [  512.148092]  action_fifos_exit+0x3240/0x37b0 [openvswitch] [  512.148125]  ? update_sd_lb_stats+0x613/0x760 [  512.148152]  ? find_busiest_group+0x3e/0x520 [  512.148177]  ? __nla_validate_parse+0x57/0x8a0 [  512.148203]  ? _cond_resched+0x15/0x40 [  512.148226]  ? genl_family_rcv_msg_attrs_parse+0xe4/0x110 [  512.148256]  genl_rcv_msg+0x1ed/0x430 [  512.148303]  ? __switch_to_asm+0x34/0x70 [  512.148326]  ? __switch_to_asm+0x40/0x70 [  512.148349]  ? __switch_to_asm+0x34/0x70 [  512.148371]  ? __switch_to_asm+0x40/0x70 [  512.148394]  ? __switch_to_asm+0x34/0x70 [  512.148416]  ? __switch_to_asm+0x40/0x70 [  512.148439]  ? genl_family_rcv_msg_attrs_parse+0x110/0x110 [  512.148470]  netlink_rcv_skb+0x4a/0x110 [  512.148492]  genl_rcv+0x24/0x40 [  512.148512]  netlink_unicast+0x1a0/0x250 [  512.148536]  netlink_sendmsg+0x2b4/0x3b0 [  512.148560]  sock_sendmsg+0x5b/0x60 [  512.148582]  ___sys_sendmsg+0x278/0x2f0 [  512.148607]  ? file_update_time+0x60/0x130 [  512.148630]  ? pipe_write+0x286/0x400 [  512.148653]  ? new_sync_write+0x12d/0x1d0 [  512.148676]  ? __sys_sendmsg+0x5e/0xa0 [  512.148697]  __sys_sendmsg+0x5e/0xa0 [  512.148720]  do_syscall_64+0x52/0x1a0 [  512.148742]  entry_SYSCALL_64_after_hwframe+0x44/0xa9 [  512.148771] RIP: 0033:0x7fbbaa6f9a6d [  512.149622] Code: b9 20 00 00 75 10 b8 2e 00 00 00 0f 05 48 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 fe f6 ff ff 48 89 04 24 b8 2e 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 47 f7 ff ff 48 89 d0 48 83 c4 08 48 3d 01 [  512.151428] RSP: 002b:00007fffca1a1100 EFLAGS: 00000293 ORIG_RAX: 000000000000002e [  512.152349] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fbbaa6f9a6d [  512.153266] RDX: 0000000000000000 RSI: 00007fffca1a1160 RDI: 0000000000000010 [  512.154184] RBP: 0000000000f42680 R08: 0000000000000000 R09: 00007fffca1a2118 [  512.155094] R10: 0000000000000008 R11: 0000000000000293 R12: 00007fffca1a1f30 [  512.155992] R13: 00007fffca1a20c0 R14: 00007fffca1a1f38 R15: 00007fffca1a15f0 [  512.156866] Modules linked in: vport_vxlan(E) vxlan(E) vport_gre(E) ip_gre(E) ip_tunnel(E) vport_geneve(E) geneve(E) ip6_udp_tunnel(E) udp_tunnel(E) openvswitch(E) nsh(E) nf_conncount(E) nf_nat_tftp(E) nf_conntrack_tftp(E) nf_nat_ftp(E) nf_conntrack_ftp(E) nf_nat(E) nf_conntrack_netlink(E) ip6table_filter(E) ip6_tables(E) iptable_filter(E) ip_tables(E) x_tables(E) ip6_gre(E) ip6_tunnel(E) tunnel6(E) gre(E) bonding(E) 8021q(E) garp(E) stp(E) mrp(E) llc(E) veth(E) nfnetlink_cttimeout(E) nfnetlink(E) nf_conntrack(E) nf_defrag_ipv6(E) nf_defrag_ipv4(E) binfmt_misc(E) intel_rapl_msr(E) snd_hda_codec_generic(E) ledtrig_audio(E) snd_hda_intel(E) snd_intel_nhlt(E) snd_hda_codec(E) intel_rapl_common(E) snd_hda_core(E) snd_hwdep(E) input_leds(E) snd_pcm(E) joydev(E) snd_timer(E) serio_raw(E) snd(E) soundcore(E) i2c_piix4(E) mac_hid(E) ib_iser(E) rdma_cm(E) iw_cm(E) ib_cm(E) ib_core(E) configfs(E) iscsi_tcp(E) libiscsi_tcp(E) libiscsi(E) scsi_transport_iscsi(E) autofs4(E) btrfs(E) zstd_decompress(E) [  512.156899]  zstd_compress(E) raid10(E) raid456(E) async_raid6_recov(E) async_memcpy(E) async_pq(E) async_xor(E) async_tx(E) xor(E) raid6_pq(E) libcrc32c(E) raid1(E) raid0(E) multipath(E) linear(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) aesni_intel(E) crypto_simd(E) qxl(E) ttm(E) cryptd(E) glue_helper(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) sysimgblt(E) fb_sys_fops(E) psmouse(E) drm(E) pata_acpi(E) floppy(E) [last unloaded: nf_conntrack_ftp] [  512.168488] ---[ end trace 26730810beeb11e1 ]--- [  512.169555] RIP: 0010:ovs_flow_tbl_remove+0x151/0x160 [openvswitch] [  512.170638] Code: 55 f7 ea 89 f0 c1 f8 1f 29 c2 39 53 10 0f 8f 6a ff ff ff 48 89 ef d1 fe 5b 5d e9 8a ed ff ff 0f 0b 0f 0b b8 18 00 00 00 eb 92 <0f> 0b 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 57 [  512.172813] RSP: 0018:ffffb637002cf8c8 EFLAGS: 00010246 [  512.173897] RAX: 0000000000000009 RBX: ffff95ebf32d23c0 RCX: ffff95ebf00e5a00 [  512.174991] RDX: ffff95ebf32d2420 RSI: 0000000000000009 RDI: ffff95ebf0dffba0 [  512.176109] RBP: ffffb637002cfb70 R08: ffff95ebf6030240 R09: ffff95ebf1643180 [  512.177229] R10: ffff95ebf283b814 R11: ffffffffc0932500 R12: ffff95ebf040a300 [  512.178364] R13: ffff95ebf0dffba0 R14: ffff95ebf283b814 R15: 0000000000000007 [  512.179530] FS:  00007fbbab3d2980(0000) GS:ffff95ebf7a80000(0000) knlGS:0000000000000000 [  512.180700] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [  512.181885] CR2: 00007fffca190ff8 CR3: 0000000232810006 CR4: 00000000001606e0 The code is hitting this: static void tbl_mask_array_del_mask(struct flow_table *tbl,                                     struct sw_flow_mask *mask) {         struct mask_array *ma = ovsl_dereference(tbl->mask_array);         int i;         /* Remove the deleted mask pointers from the array */         for (i = 0; i < ma->count; i++) {                 if (mask == ovsl_dereference(ma->masks[i]))                         goto found;         }         BUG();   <----------------------------   Here Pravin mentioned memory barrier usage in one of his replies. Perhaps that is an avenue to explore. Thanks, - Greg