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Fwd: Need some help regarding write_begin, write_end and writepage(s).
by Pranay Srivastava Dec. 29, 2016

Dec. 29, 2016

Hello, I'm trying to understand the write_begin, write_end and writepages / writepage call sequence by having a small file system coded myself. I'm not using block_write_begin / block_write_end also not using mpage_writepages as well. The issue however is that apart from write_begin and write_end, writepages never gets called. However if I do write_inode_now ( in write_end) then writepage do get called, but that's not how it's supposed to be. 1. in write_begin : I'm able to grab_cache_page_begin and returned it locked. 2. in write_end: I'm able to allocate disk space and do SetPageDirty and SetPageUptodate unlock_page and page_cache_release. 3. I also tried __mark_inode_dirty(inode, I_DIRTY_PAGES) 4. I also tried to set_page_writeback, but apparently that then makes the iput_final stuck since it waits for PG_Writeback to be cleared and that I've coded in writepage which never gets called. but writepages never gets called. Even iput_final doesn't make the write_inode_now call. Any help would be appreciated. Regards,

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disable input event device
by Ran Shalit Dec. 28, 2016

Dec. 28, 2016

Hello, Is there some way to disable input event device ? Maybe a way to disable its irq usage ? I actually rather do that from shell, not from kernel, because the kernel source is not available, and I thought that issue is also relevant in the forum. Thank you, Ranchu

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Data Type used in kernel .
by Wasim Akram Dec. 24, 2016

Dec. 24, 2016

Hi , I have seen "bool" data type is used in linux kernel code . Can we get documentation on data type used in linux kernel development ? -- Thanks and Regards Wasim Akram Ph: 7702843288

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Re: Is kernel Bugzilla a good way to start?
by Dennis Semakin Dec. 23, 2016

Dec. 23, 2016

Thanks for such detailed information. Now I have a subject what I should think about. And yes, I'll chose my own way :) 22.12.2016, 20:26, "valdis.kletnieks(a)vt.edu" <valdis.kletnieks(a)vt.edu>: > On Thu, 22 Dec 2016 19:21:18 +0300, Dennis Semakin said: >> I just thought that may be it will be quicker to start to develop for kernel. > > The quickest way to start will depend on why you're thinking of doing > kernel development at all. > > Did your boss just tell you that you have 13 weeks to ship a Linux driver > for your company's new USB widget? > > Do you have a device that Linux doesn't support? > Do you have a device that Linux *claims* to support, but it doesn't work quite right? > Do you have a device that used to work, but broke recently? > > (And yes, the approaches for the 3 are different) > > Do you have a deep desire to do something specific? "Wow, filesystems are > really cool"? "I want to push my laptop to the limits"? Something else? > > Do you just want to give back to the community? If so, skip developing and > just build and run a new linux-next kernel once a week. Lots easier to get > started, and we have plenty of developers - but lots fewer people actually > testing the 600,000 lines of new code every release. And how do I know there's > less testers than developers? Because if we had as many testers, I wouldn't > personally trip over an average of 3 to 5 bugs in linux-next per release cycle. > > Did you think it would be a babe magnet? Or looking for something to put > on your resume? > > All these have different paths.... > > (And here's the quick hint on how to get started with linux-next: > > $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > (the clone created a subdirectory, so cd to it for the following) > $ cd linux > $ git remote add linux-next git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > $ git fetch linux-next > $ git fetch --tags linux-next > ... # later on > $ git remote update > ... > > Once a week, do a 'git remote update' and build/install/run the new kernel. > If anything explodes, send an email to linux-kernel(a)vger.kernel.org > > And yes, it really *is* that easy.

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Is kernel Bugzilla a good way to start?
by Dennis Semakin Dec. 23, 2016

Dec. 23, 2016

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A question about kprobe/kretprobe and kmalloc/kzalloc
by zerons Dec. 22, 2016

Dec. 22, 2016

Hi everyone. I wrote a kernel module to test something. The module uses kprobe and kretprobe, here is a bug I met today. The pre_handler of kprobe, calls `do_something`. The probed instructions are in the middle of a function. The entry_handler of kretprobe, also calls `do_something`. `do_something` calls `kmalloc`+`memset`. Back to userspace, when I have all the functions probed, then the test program cause a high CPU usage, and the keyboard doesn't work. The system does not panic when I set softlockup_panic=1. If `do_something` is called by entry_handler of kretprobe, the module works fine. The bug happens when `do_something` called by the pre_handler of kprobe. So I use "#if 0" to locate the bug. It turns out to be `kmalloc`+`memset`. When I change that to `kzalloc`, problem solved. Then I get confused. `kzalloc` just calls `kmalloc` with a `__GFP_ZERO`. Why the bug only happens when pre_handler of kprobe gets called? Is it necessary to post the source code here? Thanks.

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Kernel thread naming convention
by Stefan Wahren Dec. 21, 2016

Dec. 21, 2016

Hi, i want to improve the naming of some kernel threads from a staging driver. Here are the current (not really self explaining) names: "VCHIQ-%d" (slot handler) "VCHIQr-%d" (recycle thread) "VCHIQs-%d" (sync thread) "VCHIQka-%d" (keep alive thread) Is there any document which describe naming convention for kernel threads? Regards Stefan

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Add me to EditorGroup on the wiki?
by Paul Wise Dec. 21, 2016

Dec. 21, 2016

Hi all, I want to add a link for 4.9 to the DevelopmentStatistics wiki page. Could someone approve my account (PaulWise)? -- bye, pabs http://bonedaddy.net/pabs3/

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Sending a patch with git-email and a gmail account
by Kevin Wilson Dec. 20, 2016

Dec. 20, 2016

Hi, I tried to send a patch with git-email account following tutorials I found on the web. I got and error saying "Unable to initialize SMTP..." I saw that many others get this error. I tried many solutions, but the only thing that worked was by going the gmail account setting, to "Sign-in & security" and to set "Allow less secure apps: " to be on. see in the "Answers" section in: http://stackoverflow.com/questions/28038662/unable-to-initialize-smtp-prope… Did anyone encounter this issue ? My question is: is there another way ? I am not happy to set "Allow less secure apps:" to be on, as this makes the security of my email account less strong, so it seems. Regards, Kevin

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kernel thread priority over user thread
by Ran Shalit Dec. 20, 2016

Dec. 20, 2016

Hello, I am trying to understand if kernel thread are always higher priority then user thread. Say, a kernel thread (created with kthread_create with SCHED_FIFO and given priority x), and user thread (created with pthread_create was created with SCHED_FIFO and given priority y), and priority of pthread is higher than kthread, would still the kernel thread get into scheduler before the user thread ? How is the scheduler decides which get first into the running state ? Regards, Ran

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