On Mon, 3 Mar 2014, Yijing Wang wrote:

Hi list,
   I found a tasklet related issue in linux-stable-rt 3.4.

And after I revert following commit, the test result seems ok(test lasted 40hours).

commit 0d9f73fc1e7270a3f8709c59c913408153d9d9f8

This commit id does not exist in the official stable rt tree.

Author: Ingo Molnar [off-list ref]
Date:   Tue Nov 29 20:18:22 2011 -0500

    tasklet: Prevent tasklets from going into infinite spin in RT

I test FC driver IO in this kernel, and after a few hours test, FC IO will abort, I found a lot of tasklet WARNING Call Trace in kernel message,like:

[2012-03-26 18:55:43][  929.252289] ------------[ cut here ]------------
[2012-03-26 18:55:43][  929.252312] WARNING: at kernel/softirq.c:773 __tasklet_action+0x51/0x1a0()

There is no warning at line 773 in any official linux-stable-rt 3.4.

[2012-03-26 18:55:43][  929.252314] Hardware name: Romley
[2012-03-26 18:55:43][  929.252316] Modules linked in: isd_fid(O) ivs_edft(O) ivs_emp(O) ivs_xnet(O) isd_rds(O) isd_idm(O) isd_dft(O) isd_base(O) sdm(O) isd_cmm(O) isd_ibc(O) isd_lib(O) xve_hab(PO) xve_net(PO) xve_cls_msg_filter(PO) xve_dscp(PO) pagepool(PO) iod(O) cmm(PO) util(PO) intel_t10(PO) itest_nid(PO) dmi(PO) bsp_adapter(PO) mpa(O) ipmi_si ipmi_devintf ipmi_msghandler iscsi_sw(PO) iscsi_prot(O) iscsi_seg(PO) iscsi_comm(PO) iscsi_initiator(PO) 8192cu(O) pciehp(PO) pcieaer(PO) pciecore(PO) drvinstallthird(PO) quark(O) sal(O) pmsas(O) foe(O) lfcoe(O) libfc(O) ib_uverbs(O) ibtgt(O) ib_srpt(O) ib_cm(O) ib_sa(O) mlx4_ib(O) ib_umad(O) ib_mad(O) mlx4_core(O) ib_core(O) drvtom(O) cxgb4(O) drvtoecore(O) fcdrv(PO) unflowlevel(PO) unfcommon(O) drvmml(PO) scsi_transport_fc scsi_tgt memtest(PO

 ) drv_iosubsys_ini(O) iocount(O) bsp_mml(PO) agetty_query(PO) cpufreq_powersave af_packet nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables xt_limit xt_tcpudp xt_multiport nf_conntr!

ack_ipv4
 nf_defrag_ipv4 xt_state nf_conntrack usr_cache(O) acpi_cpufreq mperf processor thermal_sys sg hwmon iptable_filter ip_tables x_tables ixgbe(O) igb(O) bonding(O) tg(O) netmgmt(O) drvinstall(PO) dal(PO) dca usb_storage(O) uhci_hcd ehci_hcd usbcore(O) usb_common sata_mml(O) ahci(O) libata(O) satahp(O) drvframe(PO) sd_mod crc_t10dif scsi_mod agetty_interface(PO) ext3 jbd mbcache nvram_printk(PO) os_feeddog(PO) os_debug(O) osp_proc(PO) os_rnvramdev(PO) vos(O) bsp(PO) os_die_handler(O) os_oom_handler(O) os_panic_handler(O) biosnvramdriver(O) kbox(O)
[2012-03-26 18:55:43][  929.252460] Pid: 17495, comm: 3th SioT Tainted: P           O 3.4.24.15-0.11-default #1

You have loaded a gazillion of proprietary and out of tree modules and
your kernel is tainted 'P'.

None of our problems. See:

 http://lwn.net/1999/0211/a/lt-binary.html

 https://lwn.net/Articles/287056/

I'm in a good mood today and give you some hints:

- Ingos patch is correct and always has been for RT.

- We had not a single bug report against this in almost 10 years.

- File your bugs to those who abuse our work and violate our license.

Case closed.

     tglx