Re: Where is PageHead defined in v5.0?
On Wed, 27 Mar 2019 17:23:05 -0700, Igor Pylypiv said: > and TESTPAGEFLAG defines PageHead: > #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) > > (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L215) General tip: If you're trying to find where the kernel defines FooBar, and 'git grep FooBar' only finds uses and no definitions, it probably means somebody got over-exuberant with the ## pre-processor operator 'git grep Foo##' usually reveals the culprit. ;) ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Where is PageHead defined in v5.0?
On Wed, Mar 27, 2019 at 05:23:05PM -0700, Igor Pylypiv wrote: > On Wed, Mar 27, 2019 at 4:51 PM Tobin C. Harding wrote: > > > > On Wed, Mar 27, 2019 at 07:34:58PM -0500, Jesse Simpson wrote: > > > Hi Tobin, > > > > > > I took a look on my system, and I wasn't able to find where PageHead is > > > defined either. I used grep to search for it as well as vim with ctags. > > > Maybe it's hidden away in some built-in.a or binary file. > > > > Cheers Jesse, confirmation that I've not gone mad - that's a win. > > > > I'll repost this to mm-linux tomorrow if no one on here knows. > > > > thanks, > > Tobin. > > > > ___ > > Kernelnewbies mailing list > > Kernelnewbies@kernelnewbies.org > > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > Hi Tobin and Jesse, > > Neither grep nor ctags are going to help you here :) > > PageHead is implicitly defined using macros __PAGEFLAG: > __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY) > > (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L517) > > __PAGEFLAG defines TESTPAGEFLAG: > > (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L248) > > and TESTPAGEFLAG defines PageHead: > #define TESTPAGEFLAG(uname, lname, policy) \ > static __always_inline int Page##uname(struct page *page) > > (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L215) Thanks Igor. > See, it is simple :) hmmm macros - no further comment needed :) thanks Tobin ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Where is PageHead defined in v5.0?
On Wed, Mar 27, 2019 at 4:51 PM Tobin C. Harding wrote: > > On Wed, Mar 27, 2019 at 07:34:58PM -0500, Jesse Simpson wrote: > > Hi Tobin, > > > > I took a look on my system, and I wasn't able to find where PageHead is > > defined either. I used grep to search for it as well as vim with ctags. > > Maybe it's hidden away in some built-in.a or binary file. > > Cheers Jesse, confirmation that I've not gone mad - that's a win. > > I'll repost this to mm-linux tomorrow if no one on here knows. > > thanks, > Tobin. > > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies Hi Tobin and Jesse, Neither grep nor ctags are going to help you here :) PageHead is implicitly defined using macros __PAGEFLAG: __PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY) (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L517) __PAGEFLAG defines TESTPAGEFLAG: (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L248) and TESTPAGEFLAG defines PageHead: #define TESTPAGEFLAG(uname, lname, policy) \ static __always_inline int Page##uname(struct page *page) (https://elixir.bootlin.com/linux/v5.0.5/source/include/linux/page-flags.h#L215) See, it is simple :) Thanks, Igor ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Where is PageHead defined in v5.0?
On Wed, Mar 27, 2019 at 07:34:58PM -0500, Jesse Simpson wrote: > Hi Tobin, > > I took a look on my system, and I wasn't able to find where PageHead is > defined either. I used grep to search for it as well as vim with ctags. > Maybe it's hidden away in some built-in.a or binary file. Cheers Jesse, confirmation that I've not gone mad - that's a win. I'll repost this to mm-linux tomorrow if no one on here knows. thanks, Tobin. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Where is PageHead defined in v5.0?
Hi Tobin, I took a look on my system, and I wasn't able to find where PageHead is defined either. I used grep to search for it as well as vim with ctags. Maybe it's hidden away in some built-in.a or binary file. I'm looking on version 5.0.0. Good luck, Jesse Simpson On Thu, Mar 28, 2019 at 09:26:15AM +1100, Tobin C. Harding wrote: > Hi, > > I cannot locate the definition of PageHead? It seems to have > disappeared after v4.0? I can see it defined as a function here: > > > https://elixir.bootlin.com/linux/v4.0/source/include/linux/page-flags.h#L401 > > But on the mainline (v5.1-rc2) I get: > > $ git grep ' PageHead' > include/linux/page-flags.h:int PageHeadHuge(struct page *page); > include/linux/page-flags.h: return PageHead(page); > include/linux/page-flags.h: return PageHead(page) && > test_bit(PG_double_map, [1].flags); > mm/hugetlb.c: return PageHead(page) && PagePrivate([1]); > mm/hugetlb.c: * PageHeadHuge() only returns true for hugetlbfs head page, but > not for > mm/hugetlb.c:int PageHeadHuge(struct page *page_head) > > Clearly it is defined _somewhere_. Anyone any idea what brain > dysfunction I am having right now? > > thanks, > Tobin. > > ___ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.org > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Where is PageHead defined in v5.0?
Hi, I cannot locate the definition of PageHead? It seems to have disappeared after v4.0? I can see it defined as a function here: https://elixir.bootlin.com/linux/v4.0/source/include/linux/page-flags.h#L401 But on the mainline (v5.1-rc2) I get: $ git grep ' PageHead' include/linux/page-flags.h:int PageHeadHuge(struct page *page); include/linux/page-flags.h: return PageHead(page); include/linux/page-flags.h: return PageHead(page) && test_bit(PG_double_map, [1].flags); mm/hugetlb.c: return PageHead(page) && PagePrivate([1]); mm/hugetlb.c: * PageHeadHuge() only returns true for hugetlbfs head page, but not for mm/hugetlb.c:int PageHeadHuge(struct page *page_head) Clearly it is defined _somewhere_. Anyone any idea what brain dysfunction I am having right now? thanks, Tobin. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Unexpected scheduling with mutexes
Hi, I've written a linux kernel module for an USB device. The USB driver provides 2 read-only character devices, which can be opened only exclusively by one process: - `/dev/cdev_a` - `/dev/cdev_b` The USB device can only handle one request at a time. The test setup is a follows: - Processes A reads data from 1st device: `dd if=/dev/cdev_a of=/tmp/a bs=X` - Processes B reads data from 2nd device: `dd if=/dev/cdev_b of=/tmp/b bs=X` - Process A and B run in parallel - After 10 seconds both processes are killed and size of both output files is compared. For certain values of `X` there is a significant difference in size between the two files, which I don't expect. A read call to the driver does the following: 1. `mutex_lock_interruptible(iolock)` 2. `usb_bulk_msg(dev, pipe, buf, X, timeout)` 3. `mutex_unlock(iolock)` 4. `copy_to_user(buf)` What I would expect is the following: 1. Proc A: `mutex_lock_interruptible(iolock)` 2. Proc A: `usb_bulk_msg(dev, pipe, buf, X, timeout)` 3. Scheduling: A -> B 4. Proc B: `mutex_lock_interruptible(iolock)` -> blocks 5. Scheduling: B -> A 6. Proc A: `mutex_unlock(iolock)` 7. Proc A: `copy_to_user(buf)` 8. Proc A: `mutex_lock_interruptible(iolock)` -> blocks 9. Scheduling: A -> B 10. Proc B: `usb_bulk_msg(dev, pipe, buf, X, timeout)` But what I see with ftrace is that in step 8, process A still continues. And it seems that for certain values of X the time inside the critical region is a multiple of the time slice, so that process B always gets the time slice when the critical region is blocked. What would be a best practise solution for this? I was thinking of calling `schedule()` each time after copying to user space or playing with nice values or using wait_queues? -- Dipl.-Inf. Martin Christian Senior Berater Entwicklung Hardware secunet Security Networks AG Tel.: +49 201 5454-3612, Fax +49 201 5454-1323 E-Mail: martin.christ...@secunet.com Ammonstraße 74, 01067 Dresden www.secunet.com signature.asc Description: OpenPGP digital signature ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
