Hi Russell, Thanks for looking into the issue.
This issue came up when I was doing econa (ARM) board bringup for Montavista (cavium) . Following was the bug description . Using cge60-econa-cns3420-2.6.32_110928_1104937 the kernel failed to boot with the following error: Internal error: Oops: 817 [#1] from cpu 1 PREEMPT SMP last sysfs file: /sys/devices/virtual/bdi/0:19/uevent Modules linked in: hmac ctr deflate CPU: 1 Tainted: G W (2.6.32.46.cge #1) PC is at vfp_notifier+0x48/0xbc LR is at vfp_notifier+0x44/0xbc pc : [] lr : [] psr: 60000013 sp : aeee1d30 ip : aeee1d50 fp : aeee1d4c r10: af8d6460 r9 : ffffffff r8 : af88c000 r7 : a05ba584 r6 : af88c000 r5 : 00000001 r4 : 40000000 r3 : 00000000 r2 : 00000000 r1 : 40000000 r0 : aeee0230 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 00c5787d Table: 2eeec00a DAC: 00000017 Process grep (pid: 1710, stack limit = 0xaeee0270) Stack: from cpu 1 (0xaeee1d30 to 0xaeee2000) During the bring up I used to intract with Catalin Marinas( [email protected])from ARM . He is copied on the email . Catalin has pointed out the following patch to me , which solved my problem . I just want to make sure the patch goes to mainline kernel. > The following patch provided by you solves my problem . thanks . > > http://article.gmane.org/gmane.linux.ports.arm.kernel/56631 Great. -- Catalin Regards, Shaiju. -----Original Message----- From: Russell King - ARM Linux [mailto:[email protected]] Sent: Monday, August 11, 2014 3:49 PM To: Sadasivan Shaiju Cc: [email protected] Subject: Re: PATCH -RCU locking on last_VFP_context[cpu] in vfp_notifier [2.6.32] On Mon, Aug 11, 2014 at 03:24:18PM -0700, Sadasivan Shaiju wrote: > Hi , > > I work for Montavista (Cavium Inc) as a Technical Lead . I want > to push some of the kernel patches to rt community (2.6.32 kernel > 2.6.33 rt patch) , so that It will go to the main line These > patches are reviewed and approved by our system Architect. I > request you to include in the main line . These issues were > reported during econa board bringup at montavista. > > Problem Description: > Using cge60-econa-cns3420-2.6.32, the kernel failed to boot with the > following > error: > > Internal error: Oops: 817 [#1] from cpu 1 PREEMPT SMP last sysfs file: > /sys/devices/virtual/bdi/0:19/uevent > Modules linked in: hmac ctr deflate > CPU: 1 Tainted: G W (2.6.32.46.cge #1) > PC is at vfp_notifier+0x48/0xbc > LR is at vfp_notifier+0x44/0xbc > pc : [] lr : [] psr: 60000013 > sp : aeee1d30 ip : aeee1d50 fp : aeee1d4c > r10: af8d6460 r9 : ffffffff r8 : af88c000 > r7 : a05ba584 r6 : af88c000 r5 : 00000001 r4 : 40000000 > r3 : 00000000 r2 : 00000000 r1 : 40000000 r0 : aeee0230 > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user > Control: 00c5787d Table: 2eeec00a DAC: 00000017 Process grep (pid: > 1710, stack limit = 0xaeee0270) > Stack: from cpu 1 (0xaeee1d30 to 0xaeee2000) > > Root Cause: > On the SMP architecture, last_VFP_context[cpu] becomes NULL because it > gets released on a different CPU. > > How Solved: > Fixed by exiting the thread instead of releasing the thread in the > vfp_notifier. > > I request you to include the above patch to the main line kernel . > If any questions please contact me at [email protected] > ([email protected]) This is totally insufficient for fixing a bug in a complex piece of code. You fail to explain exactly _how_ the bug arises. You say "last_VFP_context[cpu] becomes NULL because it gets released on a different CPU" - how does that happen? The only places that last_VFP_context[cpu] is set to NULL is within a cpu = get_cpu()..put_cpu() region, which by definition *must* be running on the CPU specified by 'cpu'. Without a proper diagnosis showing exactly what the race is which causes the above oops, there's nothing I can do. Sorry. -- FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
