Messages in this thread | | | Date | Fri, 4 Mar 2022 11:57:10 +0100 | Subject | Re: Regression: memory corruption on Atmel SAMA5D31 | From | Peter Rosin <> |
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On 2022-03-04 07:57, Peter Rosin wrote: > On 2022-03-04 04:55, Saravana Kannan wrote: >> On Thu, Mar 3, 2022 at 1:17 AM Peter Rosin <peda@axentia.se> wrote: >>> >>> On 2022-03-03 04:02, Saravana Kannan wrote: >>>> On Wed, Mar 2, 2022 at 4:29 PM Peter Rosin <peda@axentia.se> wrote: >>>>> >>>>> Hi! >>>>> >>>>> I'm seeing a weird problem, and I'd like some help with further >>>>> things to try in order to track down what's going on. I have >>>>> bisected the issue to >>>>> >>>>> f9aa460672c9 ("driver core: Refactor fw_devlink feature") >>>> >>>> I skimmed through your email and I'll read it more closely tomorrow, >>>> but it wasn't clear if you see this on Linus's tip of the tree too. >>>> Asking because of: >>>> https://lore.kernel.org/lkml/20210930085714.2057460-1-yangyingliang@huawei.com/ >>>> >>>> Also, a couple of other data points that _might_ help. Try kernel >>>> command line option fw_devlink=permissive vs fw_devlink=on (I forget >>>> if this was the default by 5.10) vs fw_devlink=off. >>>> >>>> I'm expecting "off" to fix the issue for you. But if permissive vs on >>>> shows a difference driver issues would start becoming a real >>>> possibility. >>>> >>>> -Saravana >>> >>> Thanks for the quick reply! I don't think I tested the very tip of >>> Linus tree before, only latest rc or something like that, but now I >>> have. I.e. >>> >>> 5859a2b19911 ("Merge branch 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace") >>> >>> It would have been typical if an issue that existed for a couple of >>> years had been fixed the last few weeks, but alas, no. >>> >>> On that kernel, and with whatever the default fw_devlink value is, the >> >> It's fw_devlink=on by default from at least 5.12-rc4 or so. >> >>> issue is there. It's a bit hard to tell if the incident probability >>> is the same when trying fw_devlink arguments, but roughly so, and I >>> do not have to wait for long to get a bad hash with the first >>> reproducer >>> >>> while :; do cat testfile | sha256sum; done >>> >>> The output is typical: >>> 78464c59faa203413aceb5f75de85bbf4cde64f21b2d0449a2d72cd2aadac2a3 - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> e03c5524ac6d16622b6c43f917aae730bc0793643f461253c4646b860c1a7215 - >>> 1b8db6218f481cb8e4316c26118918359e764cc2c29393fd9ef4f2730274bb00 - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 7d60bf848911d3b919d26941be33c928c666e9e5666f392d905af2d62d400570 - >>> 212e1fe02c24134857ffb098f1834a2d87c655e0e5b9e08d4929f49a070be97c - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 7e33e751eb99a0f63b4f7d64b0a24f3306ffaf7c4bc4b27b82e5886c8ea31bc3 - >>> d7a1f08aa9d0374d46d828fc3582f5927e076ff229b38c28089007cd0599c645 - >>> 4fc963b7c7b14df9d669500f7c062bf378ff2751f705bb91eecd20d2f896f6fe - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> 9360d886046c12d983b8bc73dd22302c57b0aafe58215700604fa977b4715fbe - >>> 4f9173f63cb2e13d1470e59e1b5c657f3b0f4f2e9a55ab6facffbb03f34ce04d - >>> >>> Setting fw_devlink=off makes no difference, AFAICT. >> >> By this, I'm assuming you set fw_devlink=off in the kernel command >> line and you still saw the corruption. > > Yes. On a bad kernel it's the same with all of the following kernel > command lines. > > console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=on ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs) > > console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=off ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs) > > console=ttyS0,115200 rw oops=panic panic=30 fw_devlink=permissive ip=none root=ubi0:rootfs ubi.mtd=6 rootfstype=ubifs noinitrd mtdparts=atmel_nand:256k(at91bootstrap),384k(barebox),256k@768k(bareboxenv),256k(bareboxenv2),128k@1536k(oftree),5M@2M(kernel),248M@8M(rootfs),-@256M(ovlfs) > >> If that's the case, I can't see how this could possibly have anything >> to do with: >> f9aa460672c9 ("driver core: Refactor fw_devlink feature") >> >> If you look at fw_devlink_link_device(), you'll see that the function >> is NOP if fw_devlink=off (the !fw_devlink_flags check). And from >> there, the rest of the code in the series doesn't run because more >> fields wouldn't get set, etc. That pretty much disables ALL the code >> in the entire series. The only remaining diff would be header file >> changes where I add/remove fields. But that's unlikely to cause any >> issues here because I'm either deleting fields that aren't used or >> adding fields that won't be used (with fw_devlink=off). I think the >> patch was just causing enough timing changes that it's masking the >> real issue. > > When I compare fw_devlink_link_device() from before and after > f9aa460672c9 ("driver core: Refactor fw_devlink feature") > I notice that you also removed an unconditional call to > device_link_add_missing_supplier_links() that was live before, > regardless of any fw_devlink parameter. > > I don't know if that's relevant. Is it? > > Not knowing this code at all, and without any serious attempt > at reading it, from here the comment of that removed function > sure looks like it might cause a different ordering before and > after the patch that is not restored with any fw_devlink > argument.
It appears that the device_link_add_missing_supplier_links() difference is not relevant after all. What actually happened in the header file in the "bad" commit was that two fields were removed (none added). Like so:
struct dev_links_info { struct list_head suppliers; struct list_head consumers; - struct list_head needs_suppliers; struct list_head defer_sync; - bool need_for_probe; enum dl_dev_state status; };
If I restore those fields on a bad kernel, the issue is no longer visible. That is true for the first bad kernel, i.e.
f9aa460672c9 ("driver core: Refactor fw_devlink feature")
and for tip of Linus as of recently, i.e.
5859a2b19911 ("Merge branch 'ucount-rlimit-fixes-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
Which is of course insane and a whole different level of bad. WTF!?!
I wonder if I can dig out the old SAMA5D31 evaluation kit and reproduce there? I think that's next on the list...
Cheers, Peter
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