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staging:rtl8192u: Possible memory leak?
by John Whitmore Sept. 26, 2018

Sept. 26, 2018

I've been going through the rtl8192u driver in drivers/staging trying to get a better understanding of the code. It's possibly not the text book network driver but it seemed as good a place to start as any. So I'm looking at the allocation function in ieee80211_module.c: struct net_device *alloc_ieee80211(int sizeof_priv) And can't figure out how there's not a possible memory leak. Either there is a memory leak or I'm misunderstanding the code. Possibly the latter is more likely but I thought I'd ask for clarification. The way I read the function the net_device is allocated with a call to alloc_etherdev() and if that call fails the code does a 'goto failed'. If the allocation of the net_device succeeds the funcion ieee80211_networks_allocate() is called, which allocates an array of 128 structures. If that allocation fails then again 'goto failed' That's all fine so far but on line 160 a third allocation is attempted and again 'goto failed' but ieee80211_network_free(ieee) is never called to clean up from the call to ieee80211_networks_allocate() This might all be a mute point as I seem to remember someone saying that memory allocation never fails in Linux and this can only happen if the first two allocations work and the third fails. Still thought I'd ask and possibly learn why I'm wrong, on so many levels ;) jwhitmore

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dev process - reduce mistakes
by Tobin C. Harding Sept. 25, 2018

Sept. 25, 2018

Hi, I'm after some advice from those more experienced with [kernel] development please. What systems do you have in place to help catch mistakes? In other words; what processes do you use when coding and submitting patches to help eliminate simple mistakes? So far my best method is getting a patch [set] ready then waiting until the next day before reviewing the set and submitting. I am facing an issue where by when doing (less than super interesting) large patch sets (like docs fixes) that by the time I get to the final review my eyes glaze over and I'm still missing mistakes. My future maintainers will thank you ;) thanks, Tobin.

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Really long lenght macros names on wlan-ng directory
by Pablo Pellecchia Sept. 24, 2018

Sept. 24, 2018

Hi all, Lately I've been doing manteinance of code on the drivers/staging/wlan-ng directory and found that there is a (seems like an auto generated code) p80211metadef.h file that is using long lenght macro names breking not only camel case convention, producing checkpatch issues when tested, but also generating a lot of "over 80 characters" warnings all over the code. Take the following as an example: DIDmib_dot11smt_dot11PrivacyTable_dot11PrivacyInvoked So I decided to do some refactor and try to make a shorter version of those macros and also avoid camel case. I came up with something like this: DIDMIB_DOT11SMT_DOT11PRCYTBL_DOTPRCYINVKD Not as short as expected, but at least we avoid camel case convention, we use an entire caps convention for macro and we keep information and context about what the macro does.Most of the "over 80 characters" issues all over the code seem to be gone, based on a quick compare between the old checkpatch test and latest one but still I have a question... Take this code as an example: result = prism2_domibset_uint32(wlandev, DIDMIB_DOT11SMT_DOT11PRCYTBL_DOT11WEBDEFKYID, sme->key_idx); Is this something I really want to fix given that the disadvantage is that by reducing the lenght I take context from what the variable does? Cases like this replicates all over the code. My idea would be to make an standard convention, something like DOT11_DIDMIB_PRCYTBL_WEBDEFKYID. So if we have the DOT11 at the beginning we know that it's a variable related to the 80211.11 standard therefore everything that comes after has to be understood in that context. That would save a lot of space but I am not sure of the reasons for which someone would need a long name as these. Maybe someone else has good reasons to keep this type of naming. My guest is that because this is an autogenerated code no one cared about naming conventions. I'm a little confused here with this so I would appreciate some advices on this. Thanks! -- Pablo --

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Pcieport driver
by Er Krishna Sept. 23, 2018

Sept. 23, 2018

Hi All, I am using 4.7 kernel. Sometimes I see prefetchable region memory is not getting allocated ...What could be possible reason and how to debug it. Pls suggest. In below snippet the red region doesn't appear sometimes after reboot. root@krishna# lspci -H1 -vs '00:03.1' 00:03.1 PCI bridge: Intel Corporation Xeon E7 v4/Xeon E5 v4/Xeon E3 v4/Xeon D PCI Express Root Port 3 (rev 03) (prog-if 00 [Normal decode]) Flags: bus master, fast devsel, latency 0, IRQ 11 Bus: primary=00, secondary=6d, subordinate=d4, sec-latency=0 Memory behind bridge: b0500000-b7afffff *Prefetchable memory behind bridge: 0000380200000000-* 000038033fffffff Capabilities: [40] Subsystem: Intel Corporation Device 0000 Capabilities: [60] MSI: Enable- Count=1/2 Maskable+ 64bit- Capabilities: [90] Express Root Port (Slot-), MSI 00 Capabilities: [e0] Power Management version 3 mgmt1-active# find /sys | grep drivers.*00:03 /sys/bus/pci/drivers/pcieport/0000:00:03.0 This problem is not consistent. It only occurs after few reboots. Does this prefetchable memory region depends on driver or it depends on Bios? Br/Krish

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is this list still alive?
by don fisher Sept. 22, 2018

Sept. 22, 2018

I have not received any updates since 12/12/16. Was I taken off the list, or is the list dead? Don

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4.19-rc3 incompatible with nvidia driver
by Daan Wendelen Sept. 21, 2018

Sept. 21, 2018

Hi, The latest nvidia driver is incompatible with 4.19-rc3 because "drm_mode_connector_update_edid_property" got renamed to "drm_connector_update_edid_property" and "drm_mode_connector_attach_encoder" to "drm_connector_attach_encoder" in the linux headers. Is this considered the fault of linux or is it considered nvidia's responsibility to fix this? If it's considered regression in the Linux kernel, to who (/ which mailing list) do I report this? Daan

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regarding const variables/structures
by inventsekar Sept. 18, 2018

Sept. 18, 2018

Hi All... One curious question.. Linux Foundation tweeted this - Meet Bhumika Goyal, age 22, from India. She has had more 340 patches accepted into the Linux kernel, which helped her land one of our two Linux Kernel Guru LiFT scholarships: https://twitter.com/linuxfoundation/status/940340927897489408?lang=en and her commits are - https://github.com/torvalds/linux/commits?author=bhumikagoyal One of my friend told me that, most/many of patches are just converting variables to "*constant*" For example - platform/chrome: chromeos_laptop: make chromeos_laptop const - Declare chromeos_laptop structures as *const *as they are only used during a copy operation. As their value is never modified during runtime, they can be made const. the question is that, how these many const variable issues are left/missed by the previous developers?!?! per my little knowledge, this task looks like a simple one.. many other Kernel Developers should have thought and made these changes long before, but i am not able to understand why this wasnt done until recently?!?!? -- Best Regards, Sekar

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IOCtl argument check
by Subhashini Rao Beerisetty Sept. 17, 2018

Sept. 17, 2018

Hi All, Can someone clarify me on IOCtl argument check. Kernel code has few IOCtl’s with a pointer to structure as an arguments. For example please consider the below mentioned IOCtl’s. #define MB862XX_L1_SET_CFG _IOW(MB862XX_BASE, 1, struct mb862xx_l1_cfg*) #define MB862XX_L1_GET_CFG _IOR(MB862XX_BASE, 0, struct mb862xx_l1_cfg*) #define AGPIOC_INFO _IOR (AGPIOC_BASE, 0, struct agp_info*) If user space passes a structure object instead of pointer to struct, what should be the return value from kernel code? How to debug this kind scenario’s if copy_{to,from}_user returns success(i.e. “0”)? The IOCtl’s are represented in 32-bits. Out of these 13 bits(bits 29-16) are reserved for size of argument. If user space passes an object instead of pointer and assume size of the structure is not equal to size of the pointer, then IOCtl decoding should result a different value, right? So for this case, does user space IOCtl calls the corresponding driver IOCtl function? Thanks

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interruptible sleep tasks
by Muni Sekhar Sept. 11, 2018

Sept. 11, 2018

Hi All, During kernel drivers testing I see lot of user mode applications blocks forever in interruptible sleep mode. Is there any way to get the corresponding kernel functions stack trace ? I see kernel has “hung_task_timeout_secs” parameter and when a task in D state did not get scheduled for more than this value report a warning. Similarly is it possible to get a warning or kernel functions stack trace when a task in “S - interruptible sleep mode” and did not get scheduled for certain duration? -- Thanks, Sekhar

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Build using O=path
by Tobin C. Harding Sept. 10, 2018

Sept. 10, 2018

Hi, I'm unable to build the kernel using the O=path/to/out option. Am I doing something brain dead? $ cd $KERNEL $ make mrproper $ cp path/to/valid/config/file .config $ make O=/abs/path/to/output ... scripts/kconfig/conf --syncconfig Kconfig *** *** Configuration file ".config" not found! *** *** Please run some configurator (e.g. "make oldconfig" or *** "make menuconfig" or "make xconfig"). ... So I tried copying the .config file to the output directory $ cp .config /abs/path/to/output $ make O=/abs/path/to/output ... Using /home/tobin/build/kernel/linux as source for kernel /home/tobin/build/kernel/linux is not clean, please run 'make mrproper' in the '/home/tobin/build/kernel/linux' directory. /home/tobin/build/kernel/linux/Makefile:1091: recipe for target 'prepare3' failed make[1]: *** [prepare3] Error 1 make[1]: Leaving directory '/home/tobin/build/kernel/output/master' Makefile:146: recipe for target 'sub-make' failed make: *** [sub-make] Error 2 Same thing if I use KBUILD_OUTPUT instead of passing O= thanks, Tobin.

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