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* [PATCH] lightweight robust futexes updatesIngo Molnar2006-03-27
| | | | | | | | | | | | | | | | | | - fix: initialize the robust list(s) to NULL in copy_process. - doc update - cleanup: rename _inuser to _inatomic - __user cleanups and other small cleanups Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Ulrich Drepper <drepper@redhat.com> Cc: Andi Kleen <ak@muc.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] lightweight robust futexes: arch defaultsIngo Molnar2006-03-27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patchset provides a new (written from scratch) implementation of robust futexes, called "lightweight robust futexes". We believe this new implementation is faster and simpler than the vma-based robust futex solutions presented before, and we'd like this patchset to be adopted in the upstream kernel. This is version 1 of the patchset. Background ---------- What are robust futexes? To answer that, we first need to understand what futexes are: normal futexes are special types of locks that in the noncontended case can be acquired/released from userspace without having to enter the kernel. A futex is in essence a user-space address, e.g. a 32-bit lock variable field. If userspace notices contention (the lock is already owned and someone else wants to grab it too) then the lock is marked with a value that says "there's a waiter pending", and the sys_futex(FUTEX_WAIT) syscall is used to wait for the other guy to release it. The kernel creates a 'futex queue' internally, so that it can later on match up the waiter with the waker - without them having to know about each other. When the owner thread releases the futex, it notices (via the variable value) that there were waiter(s) pending, and does the sys_futex(FUTEX_WAKE) syscall to wake them up. Once all waiters have taken and released the lock, the futex is again back to 'uncontended' state, and there's no in-kernel state associated with it. The kernel completely forgets that there ever was a futex at that address. This method makes futexes very lightweight and scalable. "Robustness" is about dealing with crashes while holding a lock: if a process exits prematurely while holding a pthread_mutex_t lock that is also shared with some other process (e.g. yum segfaults while holding a pthread_mutex_t, or yum is kill -9-ed), then waiters for that lock need to be notified that the last owner of the lock exited in some irregular way. To solve such types of problems, "robust mutex" userspace APIs were created: pthread_mutex_lock() returns an error value if the owner exits prematurely - and the new owner can decide whether the data protected by the lock can be recovered safely. There is a big conceptual problem with futex based mutexes though: it is the kernel that destroys the owner task (e.g. due to a SEGFAULT), but the kernel cannot help with the cleanup: if there is no 'futex queue' (and in most cases there is none, futexes being fast lightweight locks) then the kernel has no information to clean up after the held lock! Userspace has no chance to clean up after the lock either - userspace is the one that crashes, so it has no opportunity to clean up. Catch-22. In practice, when e.g. yum is kill -9-ed (or segfaults), a system reboot is needed to release that futex based lock. This is one of the leading bugreports against yum. To solve this problem, 'Robust Futex' patches were created and presented on lkml: the one written by Todd Kneisel and David Singleton is the most advanced at the moment. These patches all tried to extend the futex abstraction by registering futex-based locks in the kernel - and thus give the kernel a chance to clean up. E.g. in David Singleton's robust-futex-6.patch, there are 3 new syscall variants to sys_futex(): FUTEX_REGISTER, FUTEX_DEREGISTER and FUTEX_RECOVER. The kernel attaches such robust futexes to vmas (via vma->vm_file->f_mapping->robust_head), and at do_exit() time, all vmas are searched to see whether they have a robust_head set. Lots of work went into the vma-based robust-futex patch, and recently it has improved significantly, but unfortunately it still has two fundamental problems left: - they have quite complex locking and race scenarios. The vma-based patches had been pending for years, but they are still not completely reliable. - they have to scan _every_ vma at sys_exit() time, per thread! The second disadvantage is a real killer: pthread_exit() takes around 1 microsecond on Linux, but with thousands (or tens of thousands) of vmas every pthread_exit() takes a millisecond or more, also totally destroying the CPU's L1 and L2 caches! This is very much noticeable even for normal process sys_exit_group() calls: the kernel has to do the vma scanning unconditionally! (this is because the kernel has no knowledge about how many robust futexes there are to be cleaned up, because a robust futex might have been registered in another task, and the futex variable might have been simply mmap()-ed into this process's address space). This huge overhead forced the creation of CONFIG_FUTEX_ROBUST, but worse than that: the overhead makes robust futexes impractical for any type of generic Linux distribution. So it became clear to us, something had to be done. Last week, when Thomas Gleixner tried to fix up the vma-based robust futex patch in the -rt tree, he found a handful of new races and we were talking about it and were analyzing the situation. At that point a fundamentally different solution occured to me. This patchset (written in the past couple of days) implements that new solution. Be warned though - the patchset does things we normally dont do in Linux, so some might find the approach disturbing. Parental advice recommended ;-) New approach to robust futexes ------------------------------ At the heart of this new approach there is a per-thread private list of robust locks that userspace is holding (maintained by glibc) - which userspace list is registered with the kernel via a new syscall [this registration happens at most once per thread lifetime]. At do_exit() time, the kernel checks this user-space list: are there any robust futex locks to be cleaned up? In the common case, at do_exit() time, there is no list registered, so the cost of robust futexes is just a simple current->robust_list != NULL comparison. If the thread has registered a list, then normally the list is empty. If the thread/process crashed or terminated in some incorrect way then the list might be non-empty: in this case the kernel carefully walks the list [not trusting it], and marks all locks that are owned by this thread with the FUTEX_OWNER_DEAD bit, and wakes up one waiter (if any). The list is guaranteed to be private and per-thread, so it's lockless. There is one race possible though: since adding to and removing from the list is done after the futex is acquired by glibc, there is a few instructions window for the thread (or process) to die there, leaving the futex hung. To protect against this possibility, userspace (glibc) also maintains a simple per-thread 'list_op_pending' field, to allow the kernel to clean up if the thread dies after acquiring the lock, but just before it could have added itself to the list. Glibc sets this list_op_pending field before it tries to acquire the futex, and clears it after the list-add (or list-remove) has finished. That's all that is needed - all the rest of robust-futex cleanup is done in userspace [just like with the previous patches]. Ulrich Drepper has implemented the necessary glibc support for this new mechanism, which fully enables robust mutexes. (Ulrich plans to commit these changes to glibc-HEAD later today.) Key differences of this userspace-list based approach, compared to the vma based method: - it's much, much faster: at thread exit time, there's no need to loop over every vma (!), which the VM-based method has to do. Only a very simple 'is the list empty' op is done. - no VM changes are needed - 'struct address_space' is left alone. - no registration of individual locks is needed: robust mutexes dont need any extra per-lock syscalls. Robust mutexes thus become a very lightweight primitive - so they dont force the application designer to do a hard choice between performance and robustness - robust mutexes are just as fast. - no per-lock kernel allocation happens. - no resource limits are needed. - no kernel-space recovery call (FUTEX_RECOVER) is needed. - the implementation and the locking is "obvious", and there are no interactions with the VM. Performance ----------- I have benchmarked the time needed for the kernel to process a list of 1 million (!) held locks, using the new method [on a 2GHz CPU]: - with FUTEX_WAIT set [contended mutex]: 130 msecs - without FUTEX_WAIT set [uncontended mutex]: 30 msecs I have also measured an approach where glibc does the lock notification [which it currently does for !pshared robust mutexes], and that took 256 msecs - clearly slower, due to the 1 million FUTEX_WAKE syscalls userspace had to do. (1 million held locks are unheard of - we expect at most a handful of locks to be held at a time. Nevertheless it's nice to know that this approach scales nicely.) Implementation details ---------------------- The patch adds two new syscalls: one to register the userspace list, and one to query the registered list pointer: asmlinkage long sys_set_robust_list(struct robust_list_head __user *head, size_t len); asmlinkage long sys_get_robust_list(int pid, struct robust_list_head __user **head_ptr, size_t __user *len_ptr); List registration is very fast: the pointer is simply stored in current->robust_list. [Note that in the future, if robust futexes become widespread, we could extend sys_clone() to register a robust-list head for new threads, without the need of another syscall.] So there is virtually zero overhead for tasks not using robust futexes, and even for robust futex users, there is only one extra syscall per thread lifetime, and the cleanup operation, if it happens, is fast and straightforward. The kernel doesnt have any internal distinction between robust and normal futexes. If a futex is found to be held at exit time, the kernel sets the highest bit of the futex word: #define FUTEX_OWNER_DIED 0x40000000 and wakes up the next futex waiter (if any). User-space does the rest of the cleanup. Otherwise, robust futexes are acquired by glibc by putting the TID into the futex field atomically. Waiters set the FUTEX_WAITERS bit: #define FUTEX_WAITERS 0x80000000 and the remaining bits are for the TID. Testing, architecture support ----------------------------- I've tested the new syscalls on x86 and x86_64, and have made sure the parsing of the userspace list is robust [ ;-) ] even if the list is deliberately corrupted. i386 and x86_64 syscalls are wired up at the moment, and Ulrich has tested the new glibc code (on x86_64 and i386), and it works for his robust-mutex testcases. All other architectures should build just fine too - but they wont have the new syscalls yet. Architectures need to implement the new futex_atomic_cmpxchg_inuser() inline function before writing up the syscalls (that function returns -ENOSYS right now). This patch: Add placeholder futex_atomic_cmpxchg_inuser() implementations to every architecture that supports futexes. It returns -ENOSYS. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Acked-by: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] unify pfn_to_page: FRV pfn_to_pageKAMEZAWA Hiroyuki2006-03-27
| | | | | | | | | FRV can use generic funcs. Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] bitops: frv: use generic bitopsAkinobu Mita2006-03-26
| | | | | | | | | | | | | | | | | - remove ffz() - remove find_{next,first}{,_zero}_bit() - remove generic_ffs() - remove __ffs() - remove generic_fls64() - remove sched_find_first_bit() - remove generic_hweight{32,16,8}() - remove ext2_{set,clear,test,find_first_zero,find_next_zero}_bit() - remove minix_{test,set,test_and_clear,test,find_first_zero}_bit() Signed-off-by: Akinobu Mita <mita@miraclelinux.com> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] bitops: use non atomic operations for minix_*_bit() and ext2_*_bit()Akinobu Mita2006-03-26
| | | | | | | | | | | | | | | | Bitmap functions for the minix filesystem and the ext2 filesystem except ext2_set_bit_atomic() and ext2_clear_bit_atomic() do not require the atomic guarantees. But these are defined by using atomic bit operations on several architectures. (cris, frv, h8300, ia64, m32r, m68k, m68knommu, mips, s390, sh, sh64, sparc, sparc64, v850, and xtensa) This patch switches to non atomic bit operation. Signed-off-by: Akinobu Mita <mita@miraclelinux.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] POLLRDHUP/EPOLLRDHUP handling for half-closed devices notificationsDavide Libenzi2006-03-25
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement the half-closed devices notifiation, by adding a new POLLRDHUP (and its alias EPOLLRDHUP) bit to the existing poll/select sets. Since the existing POLLHUP handling, that does not report correctly half-closed devices, was feared to be changed, this implementation leaves the current POLLHUP reporting unchanged and simply add a new bit that is set in the few places where it makes sense. The same thing was discussed and conceptually agreed quite some time ago: http://lkml.org/lkml/2003/7/12/116 Since this new event bit is added to the existing Linux poll infrastruture, even the existing poll/select system calls will be able to use it. As far as the existing POLLHUP handling, the patch leaves it as is. The pollrdhup-2.6.16.rc5-0.10.diff defines the POLLRDHUP for all the existing archs and sets the bit in the six relevant files. The other attached diff is the simple change required to sys/epoll.h to add the EPOLLRDHUP definition. There is "a stupid program" to test POLLRDHUP delivery here: http://www.xmailserver.org/pollrdhup-test.c It tests poll(2), but since the delivery is same epoll(2) will work equally. Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] add asm-generic/mman.hMichael S. Tsirkin2006-02-15
| | | | | | | | | | | | | | Make new MADV_REMOVE, MADV_DONTFORK, MADV_DOFORK consistent across all arches. The idea is to make it possible to use them portably even before distros include them in libc headers. Move common flags to asm-generic/mman.h Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il> Cc: Roland Dreier <rolandd@cisco.com> Cc: Badari Pulavarty <pbadari@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] FRV: Use virtual interrupt disablementDavid Howells2006-02-14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the FRV arch use virtual interrupt disablement because accesses to the processor status register (PSR) are relatively slow and because we will soon have the need to deal with multiple interrupt controls at the same time (separate h/w and inter-core interrupts). The way this is done is to dedicate one of the four integer condition code registers (ICC2) to maintaining a virtual interrupt disablement state whilst inside the kernel. This uses the ICC2.Z flag (Zero) to indicate whether the interrupts are virtually disabled and the ICC2.C flag (Carry) to indicate whether the interrupts are physically disabled. ICC2.Z is set to indicate interrupts are virtually disabled. ICC2.C is set to indicate interrupts are physically enabled. Under normal running conditions Z==0 and C==1. Disabling interrupts with local_irq_disable() doesn't then actually physically disable interrupts - it merely sets ICC2.Z to 1. Should an interrupt then happen, the exception prologue will note ICC2.Z is set and branch out of line using one instruction (an unlikely BEQ). Here it will physically disable interrupts and clear ICC2.C. When it comes time to enable interrupts (local_irq_enable()), this simply clears the ICC2.Z flag and invokes a trap #2 if both Z and C flags are clear (the HI integer condition). This can be done with the TIHI conditional trap instruction. The trap then physically reenables interrupts and sets ICC2.C again. Upon returning the interrupt will be taken as interrupts will then be enabled. Note that whilst processing the trap, the whole exceptions system is disabled, and so an interrupt can't happen till it returns. If no pending interrupt had happened, ICC2.C would still be set, the HI condition would not be fulfilled, and no trap will happen. Saving interrupts (local_irq_save) is simply a matter of pulling the ICC2.Z flag out of the CCR register, shifting it down and masking it off. This gives a result of 0 if interrupts were enabled and 1 if they weren't. Restoring interrupts (local_irq_restore) is then a matter of taking the saved value mentioned previously and XOR'ing it against 1. If it was one, the result will be zero, and if it was zero the result will be non-zero. This result is then used to affect the ICC2.Z flag directly (it is a condition code flag after all). An XOR instruction does not affect the Carry flag, and so that bit of state is unchanged. The two flags can then be sampled to see if they're both zero using the trap (TIHI) as for the unconditional reenablement (local_irq_enable). This patch also: (1) Modifies the debugging stub (break.S) to handle single-stepping crossing into the trap #2 handler and into virtually disabled interrupts. (2) Removes superseded fixup pointers from the second instructions in the trap tables (there's no a separate fixup table for this). (3) Declares the trap #3 vector for use in .org directives in the trap table. (4) Moves irq_enter() and irq_exit() in do_IRQ() to avoid problems with virtual interrupt handling, and removes the duplicate code that has now been folded into irq_exit() (softirq and preemption handling). (5) Tells the compiler in the arch Makefile that ICC2 is now reserved. (6) Documents the in-kernel ABI, including the virtual interrupts. (7) Renames the old irq management functions to different names. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] FRV: Miscellaneous fixesDavid Howells2006-02-14
| | | | | | | | | | | | | | | | | | Make various alterations and fixes to the FRV arch: (1) Resyncs the FRV system call collection with the i386 arch. (2) Discards __iounmap() as it's not used. (3) Fixes the use of the SWAP/SWAPI instruction to get the arguments the right way around in atomic.h, and also to get the asm constraints correct. (4) Moves copy_to/from_user_page() to asm/cacheflush.h to be consistent with other archs. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] madvise MADV_DONTFORK/MADV_DOFORKMichael S. Tsirkin2006-02-14
| | | | | | | | | | | | | | | | | | | | | | | | Currently, copy-on-write may change the physical address of a page even if the user requested that the page is pinned in memory (either by mlock or by get_user_pages). This happens if the process forks meanwhile, and the parent writes to that page. As a result, the page is orphaned: in case of get_user_pages, the application will never see any data hardware DMA's into this page after the COW. In case of mlock'd memory, the parent is not getting the realtime/security benefits of mlock. In particular, this affects the Infiniband modules which do DMA from and into user pages all the time. This patch adds madvise options to control whether memory range is inherited across fork. Useful e.g. for when hardware is doing DMA from/into these pages. Could also be useful to an application wanting to speed up its forks by cutting large areas out of consideration. Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il> Acked-by: Hugh Dickins <hugh@veritas.com> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] include/asm-*/bitops.h: fix more "~0UL >> size" typosAlexey Dobriyan2006-02-03
| | | | | | | | | | | | | | | "[PATCH] m68knommu: fix find_next_zero_bit in bitops.h" fixed a typo in m68knommu implementation of find_next_zero_bit(). grep(1) shows that cris, frv, h8300, v850 are also affected. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Cc: Mikael Starvik <starvik@axis.com> Cc: David Howells <dhowells@redhat.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Handle TIF_RESTORE_SIGMASK for FRVDavid Howells2006-01-18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Handle TIF_RESTORE_SIGMASK as added by David Woodhouse's patch entitled: [PATCH] 2/3 Add TIF_RESTORE_SIGMASK support for arch/powerpc [PATCH] 3/3 Generic sys_rt_sigsuspend It does the following: (1) Declares TIF_RESTORE_SIGMASK for FRV. (2) Invokes it over to do_signal() when TIF_RESTORE_SIGMASK is set. (3) Makes do_signal() support TIF_RESTORE_SIGMASK, using the signal mask saved in current->saved_sigmask. (4) Discards sys_rt_sigsuspend() from the arch, using the generic one instead. (5) Makes sys_sigsuspend() save the signal mask and set TIF_RESTORE_SIGMASK rather than attempting to fudge the return registers. (6) Makes sys_sigsuspend() return -ERESTARTNOHAND rather than looping intrinsically. (7) Makes setup_frame(), setup_rt_frame() and handle_signal() return 0 or -EFAULT rather than true/false to be consistent with the rest of the kernel. Due to the fact do_signal() is then only called from one place: (8) Make do_signal() no longer have a return value is it was just being ignored; force_sig() takes care of this. (9) Discards the old sigmask argument to do_signal() as it's no longer necessary. This patch depends on the FRV signalling patches as well as the sys_rt_sigsuspend patch. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] death of get_thread_info/put_thread_infoAl Viro2006-01-12
| | | | | | | | | {get,put}_thread_info() were introduced in 2.5.4 and never had been called by anything in the tree. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Generic ioctl.hBrian Gerst2006-01-10
| | | | | | | | Most arches copied the i386 ioctl.h. Combine them into a generic header. Signed-off-by: Brian Gerst <bgerst@didntduck.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] mutex subsystem, add default include/asm-*/mutex.h filesArjan van de Ven2006-01-09
| | | | | | | | | | | | | add the per-arch mutex.h files for the remaining architectures. We default to asm-generic/mutex-dec.h, because that performs quite well on most arches. Arches that do not have atomic decrement/increment instructions should switch to mutex-xchg.h instead. Arches can also provide their own implementation for the mutex fastpath primitives. Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* [PATCH] mutex subsystem, add atomic_xchg() to all archesIngo Molnar2006-01-09
| | | | | | | add atomic_xchg() to all the architectures. Needed by the new mutex code. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org>
* [PATCH] frv: miscellaneous changesDavid Howells2006-01-08
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fix a number of miscellanous items: (1) Declare lock sections in the linker script. (2) Recurse in the correct manner in the arch makefile. (3) asm/bug.h requires asm/linkage.h to be included first. One C file puts asm/bug.h first. (4) Add an empty RTC header file to avoid missing header file errors. (5) sg_dma_address() should use the dma_address member of a scatter list. (6) Add trivial pci_unmap support. (7) Add pgprot_noncached() (8) Discard u_quad_t. (9) Use ~0UL rather than ULONG_MAX in unistd.h in case the latter isn't declared. (10) Add an empty VGA header file to avoid missing header file errors. (11) Add an XOR header file to use the generic XOR stuff. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] frv: make get_user macro cast pointersDavid Howells2006-01-08
| | | | | | | | | Make the get_user macro cast the source pointer to an appropriate type for the specified size. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] frv: add module support stubsDavid Howells2006-01-08
| | | | | | | | Add stubs for FRV module support. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] frv: supply various missing I/O access primitivesDavid Howells2006-01-08
| | | | | | | | | | | | | | | | | | | | | | Supply various I/O access primitives that are missing for the FRV arch: (*) mmiowb() (*) read*_relaxed() (*) ioport_*map() (*) ioread*(), iowrite*(), ioread*_rep() and iowrite*_rep() (*) pci_io*map() (*) check_signature() The patch also makes __is_PCI_addr() more efficient. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] frv: drop 8/16-bit xchg and cmpxchgDavid Howells2006-01-08
| | | | | | | | | Drop support for 8-bit and 16-bit xchg and cmpxchg emulation and implements 32-bit xchg with the SWAP/SWAPI instruction. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] frv: improve signal handlingDavid Howells2006-01-06
| | | | | | | | | | | | | | The attached patch improves the signal handling: (1) It makes do_signal() static as it isn't called from anywhere outside of the arch code. (2) It removes the regs argument to all the static functions within that file, using __frame instead (which is the same thing held in a global register). Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] FRV: Implement futex operations for FRVDavid Howells2006-01-06
| | | | | | | | | | The attached patch implements futex operations for the FRV architecture. The operations are applicable to both MMU and no-MMU modes; though the EFAULT handling will be a little bit of wasted space on the latter. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] atomic_long_t & include/asm-generic/atomic.h V2Christoph Lameter2006-01-06
| | | | | | | | | | | | | | | | | | | Several counters already have the need to use 64 atomic variables on 64 bit platforms (see mm_counter_t in sched.h). We have to do ugly ifdefs to fall back to 32 bit atomic on 32 bit platforms. The VM statistics patch that I am working on will also make more extensive use of atomic64. This patch introduces a new type atomic_long_t by providing definitions in asm-generic/atomic.h that works similar to the c "long" type. Its 32 bits on 32 bit platforms and 64 bits on 64 bit platforms. Also cleans up the determination of the mm_counter_t in sched.h. Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] madvise(MADV_REMOVE): remove pages from tmpfs shm backing storeBadari Pulavarty2006-01-06
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Here is the patch to implement madvise(MADV_REMOVE) - which frees up a given range of pages & its associated backing store. Current implementation supports only shmfs/tmpfs and other filesystems return -ENOSYS. "Some app allocates large tmpfs files, then when some task quits and some client disconnect, some memory can be released. However the only way to release tmpfs-swap is to MADV_REMOVE". - Andrea Arcangeli Databases want to use this feature to drop a section of their bufferpool (shared memory segments) - without writing back to disk/swap space. This feature is also useful for supporting hot-plug memory on UML. Concerns raised by Andrew Morton: - "We have no plan for holepunching! If we _do_ have such a plan (or might in the future) then what would the API look like? I think sys_holepunch(fd, start, len), so we should start out with that." - Using madvise is very weird, because people will ask "why do I need to mmap my file before I can stick a hole in it?" - None of the other madvise operations call into the filesystem in this manner. A broad question is: is this capability an MM operation or a filesytem operation? truncate, for example, is a filesystem operation which sometimes has MM side-effects. madvise is an mm operation and with this patch, it gains FS side-effects, only they're really, really significant ones." Comments: - Andrea suggested the fs operation too but then it's more efficient to have it as a mm operation with fs side effects, because they don't immediatly know fd and physical offset of the range. It's possible to fixup in userland and to use the fs operation but it's more expensive, the vmas are already in the kernel and we can use them. Short term plan & Future Direction: - We seem to need this interface only for shmfs/tmpfs files in the short term. We have to add hooks into the filesystem for correctness and completeness. This is what this patch does. - In the future, plan is to support both fs and mmap apis also. This also involves (other) filesystem specific functions to be implemented. - Current patch doesn't support VM_NONLINEAR - which can be addressed in the future. Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com> Cc: Hugh Dickins <hugh@veritas.com> Cc: Andrea Arcangeli <andrea@suse.de> Cc: Michael Kerrisk <mtk-manpages@gmx.net> Cc: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [FLS64]: generic versionStephen Hemminger2006-01-03
| | | | | Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
* [PATCH] FRV: Make the FRV arch work againDavid Howells2005-11-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The attached patch implements a bunch of small changes to the FRV arch to make it work again. It deals with the following problems: (1) SEM_DEBUG should be SEMAPHORE_DEBUG. (2) The argument list to pcibios_penalize_isa_irq() has changed. (3) CONFIG_HIGHMEM can't be used directly in #if as it may not be defined. (4) page->private is no longer directly accessible. (5) linux/hardirq.h assumes asm/hardirq.h will include linux/irq.h (6) The IDE MMIO access functions are given pointers, not integers, and so get type casting errors. (7) __pa() is passed an explicit u64 type in drivers/char/mem.c, but that can't be cast directly to a pointer on a 32-bit platform. (8) SEMAPHORE_DEBUG should not be contingent on WAITQUEUE_DEBUG as that no longer exists. (9) PREEMPT_ACTIVE is too low a value. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] atomic: inc_not_zeroNick Piggin2005-11-13
| | | | | | | | | | | Introduce an atomic_inc_not_zero operation. Make this a special case of atomic_add_unless because lockless pagecache actually wants atomic_inc_not_negativeone due to its offset refcount. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] atomic: cmpxchgNick Piggin2005-11-13
| | | | | | | | | Introduce an atomic_cmpxchg operation. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] fix remaining missing includesTim Schmielau2005-11-07
| | | | | | | | | | Fix more include file problems that surfaced since I submitted the previous fix-missing-includes.patch. This should now allow not to include sched.h from module.h, which is done by a followup patch. Signed-off-by: Tim Schmielau <tim@physik3.uni-rostock.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] semaphore: Remove __MUTEX_INITIALIZER()Arthur Othieno2005-10-30
| | | | | | | | | __MUTEX_INITIALIZER() has no users, and equates to the more commonly used DECLARE_MUTEX(), thus making it pretty much redundant. Remove it for good. Signed-off-by: Arthur Othieno <a.othieno@bluewin.ch> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] vm: remove unused/broken page_pte[_prot] macrosTejun Heo2005-10-30
| | | | | | | | | | | | | | | | | | | | | | | This patch removes page_pte_prot and page_pte macros from all architectures. Some architectures define both, some only page_pte (broken) and others none. These macros are not used anywhere. page_pte_prot(page, prot) is identical to mk_pte(page, prot) and page_pte(page) is identical to page_pte_prot(page, __pgprot(0)). * The following architectures define both page_pte_prot and page_pte arm, arm26, ia64, sh64, sparc, sparc64 * The following architectures define only page_pte (broken) frv, i386, m32r, mips, sh, x86-64 * All other architectures define neither Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] gfp_t: dma-mapping (frv)Al Viro2005-10-28
| | | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Remove unused var from asm/futex.hPaolo 'Blaisorblade' Giarrusso2005-09-21
| | | | | | | | | | | | | | | | | | | | | As recently done by Russell King for ARM, commit 4732efbeb997189d9f9b04708dc26bf8613ed721 introduces a generic asm/futex.h copied along most arches, which includes a "-ENOSYS support" to be changed if needed. However, it includes an unused var (taken from the "real" version) which GCC warns about. Remove it from all arches having that file version (i.e. same GIT id). $ git-diff-tree -r HEAD and $ git-ls-tree -r HEAD include/|grep 9feff4ce1424bc390608326240be369eb13aa648 may be more interesting than looking at the patch itself, to make sure I've just copied the arm header to all other archs having the original dummy version of this file. Cc: Jakub Jelinek <jakub@redhat.com> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] feature removal of io_remap_page_range()Randy Dunlap2005-09-13
| | | | | | | | | As written in Documentation/feature-removal-schedule.txt, remove the io_remap_page_range() kernel API. Signed-off-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Clean up struct flock64 definitionsStephen Rothwell2005-09-07
| | | | | | | | | This patch gathers all the struct flock64 definitions (and the operations), puts them under !CONFIG_64BIT and cleans up the arch files. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Clean up struct flock definitionsStephen Rothwell2005-09-07
| | | | | | | | | This patch just gathers together all the struct flock definitions except xtensa into asm-generic/fcntl.h. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Clean up the fcntl operationsStephen Rothwell2005-09-07
| | | | | | | | | This patch puts the most popular of each fcntl operation/flag into asm-generic/fcntl.h and cleans up the arch files. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Clean up the open flagsStephen Rothwell2005-09-07
| | | | | | | | | This patch puts the most popular of each open flag into asm-generic/fcntl.h and cleans up the arch files. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] Create asm-generic/fcntl.hStephen Rothwell2005-09-07
| | | | | | | | | | | | | This set of patches creates asm-generic/fcntl.h and consolidates as much as possible from the asm-*/fcntl.h files into it. This patch just gathers all the identical bits of the asm-*/fcntl.h files into asm-generic/fcntl.h. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] remove verify_area(): remove verify_area() from various uaccess.h ↵Jesper Juhl2005-09-07
| | | | | | | | | | | headers Remove the deprecated (and unused) verify_area() from various uaccess.h headers. Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] auxiliary vector cleanupsH. J. Lu2005-09-07
| | | | | | | | | | | | The size of auxiliary vector is fixed at 42 in linux/sched.h. But it isn't very obvious when looking at linux/elf.h. This patch adds AT_VECTOR_SIZE so that we can change it if necessary when a new vector is added. Because of include file ordering problems, doing this necessitated the extraction of the AT_* symbols into a standalone header file. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] FUTEX_WAKE_OP: pthread_cond_signal() speedupJakub Jelinek2005-09-07
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ATM pthread_cond_signal is unnecessarily slow, because it wakes one waiter (which at least on UP usually means an immediate context switch to one of the waiter threads). This waiter wakes up and after a few instructions it attempts to acquire the cv internal lock, but that lock is still held by the thread calling pthread_cond_signal. So it goes to sleep and eventually the signalling thread is scheduled in, unlocks the internal lock and wakes the waiter again. Now, before 2003-09-21 NPTL was using FUTEX_REQUEUE in pthread_cond_signal to avoid this performance issue, but it was removed when locks were redesigned to the 3 state scheme (unlocked, locked uncontended, locked contended). Following scenario shows why simply using FUTEX_REQUEUE in pthread_cond_signal together with using lll_mutex_unlock_force in place of lll_mutex_unlock is not enough and probably why it has been disabled at that time: The number is value in cv->__data.__lock. thr1 thr2 thr3 0 pthread_cond_wait 1 lll_mutex_lock (cv->__data.__lock) 0 lll_mutex_unlock (cv->__data.__lock) 0 lll_futex_wait (&cv->__data.__futex, futexval) 0 pthread_cond_signal 1 lll_mutex_lock (cv->__data.__lock) 1 pthread_cond_signal 2 lll_mutex_lock (cv->__data.__lock) 2 lll_futex_wait (&cv->__data.__lock, 2) 2 lll_futex_requeue (&cv->__data.__futex, 0, 1, &cv->__data.__lock) # FUTEX_REQUEUE, not FUTEX_CMP_REQUEUE 2 lll_mutex_unlock_force (cv->__data.__lock) 0 cv->__data.__lock = 0 0 lll_futex_wake (&cv->__data.__lock, 1) 1 lll_mutex_lock (cv->__data.__lock) 0 lll_mutex_unlock (cv->__data.__lock) # Here, lll_mutex_unlock doesn't know there are threads waiting # on the internal cv's lock Now, I believe it is possible to use FUTEX_REQUEUE in pthread_cond_signal, but it will cost us not one, but 2 extra syscalls and, what's worse, one of these extra syscalls will be done for every single waiting loop in pthread_cond_*wait. We would need to use lll_mutex_unlock_force in pthread_cond_signal after requeue and lll_mutex_cond_lock in pthread_cond_*wait after lll_futex_wait. Another alternative is to do the unlocking pthread_cond_signal needs to do (the lock can't be unlocked before lll_futex_wake, as that is racy) in the kernel. I have implemented both variants, futex-requeue-glibc.patch is the first one and futex-wake_op{,-glibc}.patch is the unlocking inside of the kernel. The kernel interface allows userland to specify how exactly an unlocking operation should look like (some atomic arithmetic operation with optional constant argument and comparison of the previous futex value with another constant). It has been implemented just for ppc*, x86_64 and i?86, for other architectures I'm including just a stub header which can be used as a starting point by maintainers to write support for their arches and ATM will just return -ENOSYS for FUTEX_WAKE_OP. The requeue patch has been (lightly) tested just on x86_64, the wake_op patch on ppc64 kernel running 32-bit and 64-bit NPTL and x86_64 kernel running 32-bit and 64-bit NPTL. With the following benchmark on UP x86-64 I get: for i in nptl-orig nptl-requeue nptl-wake_op; do echo time elf/ld.so --library-path .:$i /tmp/bench; \ for j in 1 2; do echo ( time elf/ld.so --library-path .:$i /tmp/bench ) 2>&1; done; done time elf/ld.so --library-path .:nptl-orig /tmp/bench real 0m0.655s user 0m0.253s sys 0m0.403s real 0m0.657s user 0m0.269s sys 0m0.388s time elf/ld.so --library-path .:nptl-requeue /tmp/bench real 0m0.496s user 0m0.225s sys 0m0.271s real 0m0.531s user 0m0.242s sys 0m0.288s time elf/ld.so --library-path .:nptl-wake_op /tmp/bench real 0m0.380s user 0m0.176s sys 0m0.204s real 0m0.382s user 0m0.175s sys 0m0.207s The benchmark is at: http://sourceware.org/ml/libc-alpha/2005-03/txt00001.txt Older futex-requeue-glibc.patch version is at: http://sourceware.org/ml/libc-alpha/2005-03/txt00002.txt Older futex-wake_op-glibc.patch version is at: http://sourceware.org/ml/libc-alpha/2005-03/txt00003.txt Will post a new version (just x86-64 fixes so that the patch applies against pthread_cond_signal.S) to libc-hacker ml soon. Attached is the kernel FUTEX_WAKE_OP patch as well as a simple-minded testcase that will not test the atomicity of the operation, but at least check if the threads that should have been woken up are woken up and whether the arithmetic operation in the kernel gave the expected results. Acked-by: Ingo Molnar <mingo@redhat.com> Cc: Ulrich Drepper <drepper@redhat.com> Cc: Jamie Lokier <jamie@shareable.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] sab: consolidate kmem_bufctl_tKyle Moffett2005-09-05
| | | | | | | | | | | This is used only in slab.c and each architecture gets to define whcih underlying type is to be used. Seems a bit silly - move it to slab.c and use the same type for all architectures: unsigned int. Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] mm: consolidate get_orderStephen Rothwell2005-09-05
| | | | | | | | | | | | Someone mentioned that almost all the architectures used basically the same implementation of get_order. This patch consolidates them into asm-generic/page.h and includes that in the appropriate places. The exceptions are ia64 and ppc which have their own (presumably optimised) versions. Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [NET]: Introduce SO_{SND,RCV}BUFFORCE socket optionsPatrick McHardy2005-08-29
| | | | | | | Allows overriding of sysctl_{wmem,rmrm}_max Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
* [PATCH] Add emergency_restart()Eric W. Biederman2005-07-26
| | | | | | | | | | | | | | | | | | When the kernel is working well and we want to restart cleanly kernel_restart is the function to use. But in many instances the kernel wants to reboot when thing are expected to be working very badly such as from panic or a software watchdog handler. This patch adds the function emergency_restart() so that callers can be clear what semantics they expect when calling restart. emergency_restart() is expected to be callable from interrupt context and possibly reliable in even more trying circumstances. This is an initial generic implementation for all architectures. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] PCI: fix up errors after dma bursting patch and CONFIG_PCI=nAndrew Morton2005-06-28
| | | | | | | | | | | | | | | | | | With CONFIG_PCI=n: In file included from include/linux/pci.h:917, from lib/iomap.c:6: include/asm/pci.h:104: warning: `enum pci_dma_burst_strategy' declared inside parameter list include/asm/pci.h:104: warning: its scope is only this definition or declaration, which is probably not what you want. include/asm/pci.h: In function `pci_dma_burst_advice': include/asm/pci.h:106: dereferencing pointer to incomplete type include/asm/pci.h:106: `PCI_DMA_BURST_INFINITY' undeclared (first use in this function) include/asm/pci.h:106: (Each undeclared identifier is reported only once include/asm/pci.h:106: for each function it appears in.) make[1]: *** [lib/iomap.o] Error 1 Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* [PATCH] PCI: DMA bursting adviceDavid S. Miller2005-06-28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After seeing, at best, "guesses" as to the following kind of information in several drivers, I decided that we really need a way for platforms to specifically give advice in this area for what works best with their PCI controller implementation. Basically, this new interface gives DMA bursting advice on PCI. There are three forms of the advice: 1) Burst as much as possible, it is not necessary to end bursts on some particular boundary for best performance. 2) Burst on some byte count multiple. A DMA burst to some multiple of number of bytes may be done, but it is important to end the burst on an exact multiple for best performance. The best example of this I am aware of are the PPC64 PCI controllers, where if you end a burst mid-cacheline then chip has to refetch the data and the IOMMU translations which hurts performance a lot. 3) Burst on a single byte count multiple. Bursts shall end exactly on the next multiple boundary for best performance. Sparc64 and Alpha's PCI controllers operate this way. They disconnect any device which tries to burst across a cacheline boundary. Actually, newer sparc64 PCI controllers do not have this behavior. That is why the "pdev" is passed into the interface, so I can add code later to check which PCI controller the system is using and give advice accordingly. Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* [PATCH] streamline preempt_count type across archsJesper Juhl2005-06-23
| | | | | | | | | | | | | | | | | | | The preempt_count member of struct thread_info is currently either defined as int, unsigned int or __s32 depending on arch. This patch makes the type of preempt_count an int on all archs. Having preempt_count be an unsigned type prevents the catching of preempt_count < 0 bugs, and using int on some archs and __s32 on others is not exactely "neat" - much nicer when it's just int all over. A previous version of this patch was already ACK'ed by Robert Love, and the only change in this version of the patch compared to the one he ACK'ed is that this one also makes sure the preempt_count member is consistently commented. Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>