- 02 Jun, 2016 2 commits
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Liviu Dudau authored
Since commit 4dfd6486 ("drm: Use vblank timestamps to guesstimate how many vblanks were missed"), the DRM framework can cope with devices that don't have a hardware counter for vsync events without having to keep the vsync interrupts enabled all the time. Drivers handling such hardware should use drm_vblank_no_hw_counter() function for their ->get_vblank_counter hook. Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by:
Liviu Dudau <Liviu.Dudau@arm.com> Signed-off-by:
Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1464795342-32297-1-git-send-email-Liviu.Dudau@arm.com
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Boris Brezillon authored
Fallback drm_atomic_helper_best_encoder() is funcs->best_encoder() is NULL so that DRM drivers can leave this hook unassigned if they know they want to use drm_atomic_helper_best_encoder(). Signed-off-by:
Boris Brezillon <boris.brezillon@free-electrons.com> Signed-off-by:
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- 01 Jun, 2016 3 commits
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git://anongit.freedesktop.org/drm-intelDave Airlie authored
drm-intel-next-2016-05-22: - cmd-parser support for direct reg->reg loads (Ken Graunke) - better handle DP++ smart dongles (Ville) - bxt guc fw loading support (Nick Hoathe) - remove a bunch of struct typedefs from dpll code (Ander) - tons of small work all over to avoid casting between drm_device and the i915 dev struct (Tvrtko&Chris) - untangle request retiring from other operations, also fixes reset stat corner cases (Chris) - skl atomic watermark support from Matt Roper, yay! - various wm handling bugfixes from Ville - big pile of cdclck rework for bxt/skl (Ville) - CABC (Content Adaptive Brigthness Control) for dsi panels (Jani&Deepak M) - nonblocking atomic commits for plane-only updates (Maarten Lankhorst) - bunch of PSR fixes&improvements - untangle our map/pin/sg_iter code a bit (Dave Gordon) drm-intel-next-2016-05-08: - refactor stolen quirks to share code between early quirks and i915 (Joonas) - refactor gem BO/vma funcstion (Tvrtko&Dave) - backlight over DPCD support (Yetunde Abedisi) - more dsi panel sequence support (Jani) - lots of refactoring around handling iomaps, vma, ring access and related topics culmulating in removing the duplicated request tracking in the execlist code (Chris & Tvrtko) includes a small patch for core iomapping code - hw state readout for bxt dsi (Ramalingam C) - cdclk cleanups (Ville) - dedupe chv pll code a bit (Ander) - enable semaphores on gen8+ for legacy submission, to be able to have a direct comparison against execlist on the same platform (Chris) Not meant to be used for anything else but performance tuning - lvds border bit hw state checker fix (Jani) - rpm vs. shrinker/oom-notifier fixes (Praveen Paneri) - l3 tuning (Imre) - revert mst dp audio, it's totally non-functional and crash-y (Lyude) - first official dmc for kbl (Rodrigo) - and tons of small things all over as usual * 'drm-intel-next' of git://anongit.freedesktop.org/drm-intel: (194 commits) drm/i915: Revert async unpin and nonblocking atomic commit drm/i915: Update DRIVER_DATE to 20160522 drm/i915: Inline sg_next() for the optimised SGL iterator drm/i915: Introduce & use new lightweight SGL iterators drm/i915: optimise i915_gem_object_map() for small objects drm/i915: refactor i915_gem_object_pin_map() drm/i915/psr: Implement PSR2 w/a for gen9 drm/i915/psr: Use ->get_aux_send_ctl functions drm/i915/psr: Order DP aux transactions correctly drm/i915/psr: Make idle_frames sensible again drm/i915/psr: Try to program link training times correctly drm/i915/userptr: Convert to drm_i915_private drm/i915: Allow nonblocking update of pageflips. drm/i915: Check for unpin correctness. Reapply "drm/i915: Avoid stalling on pending flips for legacy cursor updates" drm/i915: Make unpin async. drm/i915: Prepare connectors for nonblocking checks. drm/i915: Pass atomic states to fbc update functions. drm/i915: Remove reset_counter from intel_crtc. drm/i915: Remove queue_flip pointer. ...
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git://anongit.freedesktop.org/drm-intelDave Airlie authored
Frist -misc pull for 4.8, with pretty much just random all over plus a few more lockless gem BO patches acked/reviewed by driver maintainers. I'm starting a bit earlier this time around because there's a few invasive patch series to land (nonblocking atomic prep work, fence prep work, rst/sphinx kerneldoc finally happening) and I need a baseline with all the branches merged. * tag 'topic/drm-misc-2016-06-01' of git://anongit.freedesktop.org/drm-intel: (21 commits) drm/vc4: Use lockless gem BO free callback drm/vc4: Use drm_gem_object_unreference_unlocked drm: Initialize a linear gamma table by default drm/vgem: Use lockless gem BO free callback drm/qxl: Don't set a gamma table size drm/msm: Nuke dummy gamma_set/get functions drm/cirrus: Drop redundnant gamma size check drm/fb-helper: Remove dead code in setcolreg drm/mediatek: Use lockless gem BO free callback drm/hisilicon: Use lockless gem BO free callback drm/hlcd: Use lockless gem BO free callback vga_switcheroo: Support deferred probing of audio clients vga_switcheroo: Add helper for deferred probing virtio-gpu: fix output lookup drm/doc: Unify KMS Locking docs drm/atomic-helper: Do not call ->mode_fixup for CRTC which will be disabled Fix annoyingly awkward typo in drm_edid_load.c drm/doc: Drop vblank_disable_allow wording drm: use seqlock for vblank time/count drm/mm: avoid possible null pointer dereference ...
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Daniel Vetter authored
This reverts the following patches: d55dbd06 drm/i915: Allow nonblocking update of pageflips. 15c86bdb drm/i915: Check for unpin correctness. 95c2ccdc Reapply "drm/i915: Avoid stalling on pending flips for legacy cursor updates" a6747b73 drm/i915: Make unpin async. 03f476e1 drm/i915: Prepare connectors for nonblocking checks. 2099deff drm/i915: Pass atomic states to fbc update functions. ee7171af drm/i915: Remove reset_counter from intel_crtc. 2ee004f7 drm/i915: Remove queue_flip pointer. b8d2afae drm/i915: Remove use_mmio_flip kernel parameter. 8dd634d9 drm/i915: Remove cs based page flip support. 143f73b3 drm/i915: Rework intel_crtc_page_flip to be almost atomic, v3. 84fc494b drm/i915: Add the exclusive fence to plane_state. 6885843a drm/i915: Convert flip_work to a list. aa420ddd drm/i915: Allow mmio updates on all platforms, v2. afee4d87 Revert "drm/i915: Avoid stalling on pending flips for legacy cursor updates" "drm/i915: Allow nonblocking update of pageflips" should have been split up, misses a proper commit message and seems to cause issues in the legacy page_flip path as demonstrated by kms_flip. "drm/i915: Make unpin async" doesn't handle the unthrottled cursor updates correctly, leading to an apparent pin count leak. This is caught by the WARN_ON in i915_gem_object_do_pin which screams if we have more than DRM_I915_GEM_OBJECT_MAX_PIN_COUNT pins. Unfortuantely we can't just revert these two because this patch series came with a built-in bisect breakage in the form of temporarily removing the unthrottled cursor update hack for legacy cursor ioctl. Therefore there's no other option than to revert the entire pile :( There's one tiny conflict in intel_drv.h due to other patches, nothing serious. Normally I'd wait a bit longer with doing a maintainer revert, but since the minimal set of patches we need to revert (due to the bisect breakage) is so big, time is running out fast. And very soon (especially after a few attempts at fixing issues) it'll be really hard to revert things cleanly. Lessons learned: - Not a good idea to rush the review (done by someone fairly new to the area) and not make sure domain experts had a chance to read it. - Patches should be properly split up. I only looked at the two patches that should be reverted in detail, but both look like the mix up different things in one patch. - Patches really should have proper commit messages. Especially when doing more than one thing, and especially when touching critical and tricky core code. - Building a patch series and r-b stamping it when it has a built-in bisect breakage is not a good idea. - I also think we need to stop building up technical debt by postponing atomic igt testcases even longer. I think it's clear that there's enough corner cases in this beast that we really need to have the testcases _before_ the next step lands. (cherry picked from commit 5a21b665 from drm-intel-next-queeud) Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Patrik Jakobsson <patrik.jakobsson@linux.intel.com> Cc: John Harrison <John.C.Harrison@Intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Acked-by:
Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Acked-by:
Ville Syrjälä <ville.syrjala@linux.intel.com> Acked-by:
Dave Airlie <airlied@redhat.com> Acked-by:
Jani Nikula <jani.nikula@linux.intel.com> Signed-off-by:
Daniel Vetter <daniel.vetter@intel.com>
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- 31 May, 2016 14 commits
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Daniel Vetter authored
No dev->struct_mutex anywhere to be seen. Cc: Eric Anholt <eric@anholt.net> Reviewed-by:
Eric Anholt <eric@anholt.net> Signed-off-by:
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Daniel Vetter authored
Since my last struct_mutex crusade someone escaped! This already has the advantage that for the common case when someone else holds a ref the unref won't even acquire dev->struct_mutex. And I'm working on code to allow drivers to completely opt-out of any and all dev->struct_mutex usage, but that only works if they use the _unlocked variants everywhere. v2: Drop comment too. v3: Drop the other comment too. Cc: Eric Anholt <eric@anholt.net> Reviewed-by:
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Daniel Vetter authored
Code stolen from gma500. This is just a minor bit of safety code that I spotted and figured it might be useful if we put it into the core. This is to make the get_gamma ioctl reflect likely reality even before the first set_gamma ioctl call. v2 on irc: Extend commit message per Maarten's suggestions. Reviewed-by:
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Daniel Vetter authored
No dev->struct_mutex anywhere to be seen. Cc: seanpaul@chromium.org Signed-off-by:
Sean Paul <seanpaul@chromium.org> Signed-off-by:
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Daniel Vetter authored
qxl doesn't have any functions for setting the gamma table, so this is completely defunct. Not nice to lie to userspace, so let's stop! Cc: Dave Airlie <airlied@redhat.com> Signed-off-by:
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Daniel Vetter authored
Again the fbdev emulation gamma_set/get functions are only needed for drivers that try to also use 8bpp paletted mode. Which msm doesn't, so this is dead code. Let's rip it out. Cc: Rob Clark <robdclark@gmail.com> Signed-off-by:
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Daniel Vetter authored
The core does this for us already. Cc: Dave Airlie <airlied@redhat.com> Signed-off-by:
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Daniel Vetter authored
DRM fbdev emulation only supports pallete_color with depth == 8, and truecolor with depth > 8. Handling depth == 16 for palettes is hence dead code, let's remove it. Signed-off-by:
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Daniel Vetter authored
No dev->struct_mutex anywhere to be seen. Cc: Philipp Zabel <p.zabel@pengutronix.de> Signed-off-by:
Philipp Zabel <p.zabel@pengutronix.de> Signed-off-by:
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Daniel Vetter authored
No dev->struct_mutex anywhere to be seen. Cc: Xinliang Liu <xinliang.liu@linaro.org> Cc: Xinwei Kong <kong.kongxinwei@hisilicon.com> Signed-off-by:
Xinwei Kong <kong.kongxinwei@hisilicon.com> Signed-off-by:
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Daniel Vetter authored
No dev->struct_mutex anywhere to be seen. Cc: Liviu Dudau <Liviu.Dudau@arm.com> Signed-off-by:
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Lukas Wunner authored
Daniel Vetter pointed out that vga_switcheroo_client_probe_defer() could be needed by audio clients as well. To avoid mistakes when someone adds conditions for these in the future, constrain the single existing condition to VGA clients by checking for PCI_BASE_CLASS_DISPLAY. This encompasses both PCI_CLASS_DISPLAY_VGA as well as PCI_CLASS_DISPLAY_3D, which is used by some Nvidia Optimus GPUs. Any future checks for audio clients should then be constrained to PCI_BASE_CLASS_MULTIMEDIA. v6: Spun out from commit introducing vga_switcheroo_client_probe_defer() to keep it a pure refactoring change. (Emil Velikov, Jani Nikula) Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Emil Velikov <emil.l.velikov@gmail.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Signed-off-by:Lukas Wunner <lukas@wunner.de> Signed-off-by:
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Lukas Wunner authored
So far we've got one condition when DRM drivers need to defer probing on a dual GPU system and it's coded separately into each of the relevant drivers. As suggested by Daniel Vetter, deduplicate that code in the drivers and move it to a new vga_switcheroo helper. This yields better encapsulation of concepts and lets us add further checks in a central place. (The existing check pertains to pre-retina MacBook Pros and an additional check is expected to be needed for retinas.) One might be tempted to check deferred probing conditions in vga_switcheroo_register_client(), but this is usually called fairly late during driver load. The GPU is fully brought up and ready for switching at that point. On boot the ->probe hook is potentially called dozens of times until it finally succeeds, and each time we'd repeat bringup and teardown of the GPU, lengthening boot time considerably and cluttering logfiles. A separate helper is therefore needed which can be called right at the beginning of the ->probe hook. Note that amdgpu currently does not call this helper as the AMD GPUs built into MacBook Pros are only supported by radeon so far. v2: This helper could eventually be used by audio clients as well, so rephrase kerneldoc to refer to "client" instead of "GPU" and move the single existing check in an if block specific to PCI_CLASS_DISPLAY_VGA devices. Move documentation on that check from kerneldoc to a comment. (Daniel Vetter) v3: Mandate in kerneldoc that registration of client shall only happen after calling this helper. (Daniel Vetter) v4: Rebase on 412c8f7d ("drm/radeon: Return -EPROBE_DEFER when amdkfd not loaded") v5: Some Optimus GPUs use PCI_CLASS_DISPLAY_3D, make sure those are matched as well. (Emil Velikov) v6: The if-condition referring to PCI_BASE_CLASS_DISPLAY may be considered a functional change. Move to a separate commit to keep this a pure refactoring change. (Emil Velikov, Jani Nikula) Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: -
Gerd Hoffmann authored
Needed for multihead setups where we can have disabled outputs and therefore plane->crtc can be NULL. Signed-off-by:
Gerd Hoffmann <kraxel@redhat.com> Signed-off-by:
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- 30 May, 2016 3 commits
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Daniel Vetter authored
Signed-off-by:
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Liu Ying authored
When a CRTC is going to be disabled, it's state may contain a display mode with zeroed content. This could be reproduced by HDMI cable hotplug out operation with legacy fbdev support in dual display cases. It would confuse driver's CRTC callback ->mode_fixup and make the total state be rejected. So, let's don't call the callback for the CRTC. Signed-off-by:
Liu Ying <gnuiyl@gmail.com> Signed-off-by:
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Valdis Kletnieks authored
Fix egregious typo in comment. Signed-off-by:
Valdis Kletnieks <valdis.kletnieks@vt.edu> Signed-off-by:
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- 29 May, 2016 3 commits
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Linus Torvalds authored
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George Spelvin authored
The self-test was updated to cover zero-length strings; the function needs to be updated, too. Reported-by:
Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by:
George Spelvin <linux@sciencehorizons.net> Fixes: fcfd2fbf ("fs/namei.c: Add hashlen_string() function") Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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George Spelvin authored
The original name was simply hash_string(), but that conflicted with a function with that name in drivers/base/power/trace.c, and I decided that calling it "hashlen_" was better anyway. But you have to do it in two places. [ This caused build errors for architectures that don't define CONFIG_DCACHE_WORD_ACCESS - Linus ] Signed-off-by:
Guenter Roeck <linux@roeck-us.net> Fixes: fcfd2fbf ("fs/namei.c: Add hashlen_string() function") Signed-off-by:
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- 28 May, 2016 15 commits
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Mikulas Patocka authored
The HPFS filesystem used generic_show_options to produce string that is displayed in /proc/mounts. However, there is a problem that the options may disappear after remount. If we mount the filesystem with option1 and then remount it with option2, /proc/mounts should show both option1 and option2, however it only shows option2 because the whole option string is replaced with replace_mount_options in hpfs_remount_fs. To fix this bug, implement the hpfs_show_options function that prints options that are currently selected. Signed-off-by:
Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by:
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Mikulas Patocka authored
Commit c8f33d0b ("affs: kstrdup() memory handling") checks if the kstrdup function returns NULL due to out-of-memory condition. However, if we are remounting a filesystem with no change to filesystem-specific options, the parameter data is NULL. In this case, kstrdup returns NULL (because it was passed NULL parameter), although no out of memory condition exists. The mount syscall then fails with ENOMEM. This patch fixes the bug. We fail with ENOMEM only if data is non-NULL. The patch also changes the call to replace_mount_options - if we didn't pass any filesystem-specific options, we don't call replace_mount_options (thus we don't erase existing reported options). Fixes: c8f33d0b ("affs: kstrdup() memory handling") Signed-off-by:
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Mikulas Patocka authored
Commit ce657611 ("hpfs: kstrdup() out of memory handling") checks if the kstrdup function returns NULL due to out-of-memory condition. However, if we are remounting a filesystem with no change to filesystem-specific options, the parameter data is NULL. In this case, kstrdup returns NULL (because it was passed NULL parameter), although no out of memory condition exists. The mount syscall then fails with ENOMEM. This patch fixes the bug. We fail with ENOMEM only if data is non-NULL. The patch also changes the call to replace_mount_options - if we didn't pass any filesystem-specific options, we don't call replace_mount_options (thus we don't erase existing reported options). Fixes: ce657611 ("hpfs: kstrdup() out of memory handling") Signed-off-by:
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git://git.linux-mips.org/pub/scm/ralf/upstream-linusLinus Torvalds authored
Pull more MIPS updates from Ralf Baechle: "This is the secondnd batch of MIPS patches for 4.7. Summary: CPS: - Copy EVA configuration when starting secondary VPs. EIC: - Clear Status IPL. Lasat: - Fix a few off by one bugs. lib: - Mark intrinsics notrace. Not only are the intrinsics uninteresting, it would cause infinite recursion. MAINTAINERS: - Add file patterns for MIPS BRCM device tree bindings. - Add file patterns for mips device tree bindings. MT7628: - Fix MT7628 pinmux typos. - wled_an pinmux gpio. - EPHY LEDs pinmux support. Pistachio: - Enable KASLR VDSO: - Build microMIPS VDSO for microMIPS kernels. - Fix aliasing warning by building with `-fno-strict-aliasing' for debugging but also tracing them might result in recursion. Misc: - Add missing FROZEN hotplug notifier transitions. - Fix clk binding example for varioius PIC32 devices. - Fix cpu interrupt controller node-names in the DT files. - Fix XPA CPU feature separation. - Fix write_gc0_* macros when writing zero. - Add inline asm encoding helpers. - Add missing VZ accessor microMIPS encodings. - Fix little endian microMIPS MSA encodings. - Add 64-bit HTW fields and fix its configuration. - Fix sigreturn via VDSO on microMIPS kernel. - Lots of typo fixes. - Add definitions of SegCtl registers and use them" * 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (49 commits) MIPS: Add missing FROZEN hotplug notifier transitions MIPS: Build microMIPS VDSO for microMIPS kernels MIPS: Fix sigreturn via VDSO on microMIPS kernel MIPS: devicetree: fix cpu interrupt controller node-names MIPS: VDSO: Build with `-fno-strict-aliasing' MIPS: Pistachio: Enable KASLR MIPS: lib: Mark intrinsics notrace MIPS: Fix 64-bit HTW configuration MIPS: Add 64-bit HTW fields MAINTAINERS: Add file patterns for mips device tree bindings MAINTAINERS: Add file patterns for mips brcm device tree bindings MIPS: Simplify DSP instruction encoding macros MIPS: Add missing tlbinvf/XPA microMIPS encodings MIPS: Fix little endian microMIPS MSA encodings MIPS: Add missing VZ accessor microMIPS encodings MIPS: Add inline asm encoding helpers MIPS: Spelling fix lets -> let's MIPS: VR41xx: Fix typo MIPS: oprofile: Fix typo MIPS: math-emu: Fix typo ... -
Guenter Roeck authored
Various builds (such as i386:allmodconfig) fail with fs/binfmt_aout.c:133:2: error: expected identifier or '(' before 'return' fs/binfmt_aout.c:134:1: error: expected identifier or '(' before '}' token [ Oops. My bad, I had stupidly thought that "allmodconfig" covered this on x86-64 too, but it obviously doesn't. Egg on my face. - Linus ] Fixes: 5d22fc25 ("mm: remove more IS_ERR_VALUE abuses") Signed-off-by: -
git://ftp.sciencehorizons.net/linuxLinus Torvalds authored
Pull string hash improvements from George Spelvin: "This series does several related things: - Makes the dcache hash (fs/namei.c) useful for general kernel use. (Thanks to Bruce for noticing the zero-length corner case) - Converts the string hashes in <linux/sunrpc/svcauth.h> to use the above. - Avoids 64-bit multiplies in hash_64() on 32-bit platforms. Two 32-bit multiplies will do well enough. - Rids the world of the bad hash multipliers in hash_32. This finishes the job started in commit 689de1d6 ("Minimal fix-up of bad hashing behavior of hash_64()") The vast majority of Linux architectures have hardware support for 32x32-bit multiply and so derive no benefit from "simplified" multipliers. The few processors that do not (68000, h8/300 and some models of Microblaze) have arch-specific implementations added. Those patches are last in the series. - Overhauls the dcache hash mixing. The patch in commit 0fed3ac8 ("namei: Improve hash mixing if CONFIG_DCACHE_WORD_ACCESS") was an off-the-cuff suggestion. Replaced with a much more careful design that's simultaneously faster and better. (My own invention, as there was noting suitable in the literature I could find. Comments welcome!) - Modify the hash_name() loop to skip the initial HASH_MIX(). This would let us salt the hash if we ever wanted to. - Sort out partial_name_hash(). The hash function is declared as using a long state, even though it's truncated to 32 bits at the end and the extra internal state contributes nothing to the result. And some callers do odd things: - fs/hfs/string.c only allocates 32 bits of state - fs/hfsplus/unicode.c uses it to hash 16-bit unicode symbols not bytes - Modify bytemask_from_count to handle inputs of 1..sizeof(long) rather than 0..sizeof(long)-1. This would simplify users other than full_name_hash" Special thanks to Bruce Fields for testing and finding bugs in v1. (I learned some humbling lessons about "obviously correct" code.) On the arch-specific front, the m68k assembly has been tested in a standalone test harness, I've been in contact with the Microblaze maintainers who mostly don't care, as the hardware multiplier is never omitted in real-world applications, and I haven't heard anything from the H8/300 world" * 'hash' of git://ftp.sciencehorizons.net/linux: h8300: Add <asm/hash.h> microblaze: Add <asm/hash.h> m68k: Add <asm/hash.h> <linux/hash.h>: Add support for architecture-specific functions fs/namei.c: Improve dcache hash function Eliminate bad hash multipliers from hash_32() and hash_64() Change hash_64() return value to 32 bits <linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string() fs/namei.c: Add hashlen_string() function Pull out string hash to <linux/stringhash.h> -
George Spelvin authored
This will improve the performance of hash_32() and hash_64(), but due to complete lack of multi-bit shift instructions on H8, performance will still be bad in surrounding code. Designing H8-specific hash algorithms to work around that is a separate project. (But if the maintainers would like to get in touch...) Signed-off-by: -
George Spelvin authored
Microblaze is an FPGA soft core that can be configured various ways. If it is configured without a multiplier, the standard __hash_32() will require a call to __mulsi3, which is a slow software loop. Instead, use a shift-and-add sequence for the constant multiply. GCC knows how to do this, but it's not as clever as some. Signed-off-by: -
George Spelvin authored
This provides a multiply by constant GOLDEN_RATIO_32 = 0x61C88647 for the original mc68000, which lacks a 32x32-bit multiply instruction. Yes, the amount of optimization effort put in is excessive. :-) Shift-add chain found by Yevgen Voronenko's Hcub algorithm at http://spiral.ece.cmu.edu/mcm/gen.htmlSigned-off-by:
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George Spelvin authored
This is just the infrastructure; there are no users yet. This is modelled on CONFIG_ARCH_RANDOM; a CONFIG_ symbol declares the existence of <asm/hash.h>. That file may define its own versions of various functions, and define HAVE_* symbols (no CONFIG_ prefix!) to suppress the generic ones. Included is a self-test (in lib/test_hash.c) that verifies the basics. It is NOT in general required that the arch-specific functions compute the same thing as the generic, but if a HAVE_* symbol is defined with the value 1, then equality is tested. Signed-off-by: -
George Spelvin authored
Patch 0fed3ac8 improved the hash mixing, but the function is slower than necessary; there's a 7-instruction dependency chain (10 on x86) each loop iteration. Word-at-a-time access is a very tight loop (which is good, because link_path_walk() is one of the hottest code paths in the entire kernel), and the hash mixing function must not have a longer latency to avoid slowing it down. There do not appear to be any published fast hash functions that: 1) Operate on the input a word at a time, and 2) Don't need to know the length of the input beforehand, and 3) Have a single iterated mixing function, not needing conditional branches or unrolling to distinguish different loop iterations. One of the algorithms which comes closest is Yann Collet's xxHash, but that's two dependent multiplies per word, which is too much. The key insights in this design are: 1) Barring expensive ops like multiplies, to diffuse one input bit across 64 bits of hash state takes at least log2(64) = 6 sequentially dependent instructions. That is more cycles than we'd like. 2) An operation like "hash ^= hash << 13" requires a second temporary register anyway, and on a 2-operand machine like x86, it's three instructions. 3) A better use of a second register is to hold a two-word hash state. With careful design, no temporaries are needed at all, so it doesn't increase register pressure. And this gets rid of register copying on 2-operand machines, so the code is smaller and faster. 4) Using two words of state weakens the requirement for one-round mixing; we now have two rounds of mixing before cancellation is possible. 5) A two-word hash state also allows operations on both halves to be done in parallel, so on a superscalar processor we get more mixing in fewer cycles. I ended up using a mixing function inspired by the ChaCha and Speck round functions. It is 6 simple instructions and 3 cycles per iteration (assuming multiply by 9 can be done by an "lea" instruction): x ^= *input++; y ^= x; x = ROL(x, K1); x += y; y = ROL(y, K2); y *= 9; Not only is this reversible, two consecutive rounds are reversible: if you are given the initial and final states, but not the intermediate state, it is possible to compute both input words. This means that at least 3 words of input are required to create a collision. (It also has the property, used by hash_name() to avoid a branch, that it hashes all-zero to all-zero.) The rotate constants K1 and K2 were found by experiment. The search took a sample of random initial states (I used 1023) and considered the effect of flipping each of the 64 input bits on each of the 128 output bits two rounds later. Each of the 8192 pairs can be considered a biased coin, and adding up the Shannon entropy of all of them produces a score. The best-scoring shifts also did well in other tests (flipping bits in y, trying 3 or 4 rounds of mixing, flipping all 64*63/2 pairs of input bits), so the choice was made with the additional constraint that the sum of the shifts is odd and not too close to the word size. The final state is then folded into a 32-bit hash value by a less carefully optimized multiply-based scheme. This also has to be fast, as pathname components tend to be short (the most common case is one iteration!), but there's some room for latency, as there is a fair bit of intervening logic before the hash value is used for anything. (Performance verified with "bonnie++ -s 0 -n 1536:-2" on tmpfs. I need a better benchmark; the numbers seem to show a slight dip in performance between 4.6.0 and this patch, but they're too noisy to quote.) Special thanks to Bruce fields for diligent testing which uncovered a nasty fencepost error in an earlier version of this patch. [checkpatch.pl formatting complaints noted and respectfully disagreed with.] Signed-off-by:
J. Bruce Fields <bfields@redhat.com>
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George Spelvin authored
The "simplified" prime multipliers made very bad hash functions, so get rid of them. This completes the work of 689de1d6. To avoid the inefficiency which was the motivation for the "simplified" multipliers, hash_64() on 32-bit systems is changed to use a different algorithm. It makes two calls to hash_32() instead. drivers/media/usb/dvb-usb-v2/af9015.c uses the old GOLDEN_RATIO_PRIME_32 for some horrible reason, so it inherits a copy of the old definition. Signed-off-by:
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George Spelvin authored
That's all that's ever asked for, and it makes the return type of hash_long() consistent. It also allows (upcoming patch) an optimized implementation of hash_64 on 32-bit machines. I tried adding a BUILD_BUG_ON to ensure the number of bits requested was never more than 32 (most callers use a compile-time constant), but adding <linux/bug.h> to <linux/hash.h> breaks the tools/perf compiler unless tools/perf/MANIFEST is updated, and understanding that code base well enough to update it is too much trouble. I did the rest of an allyesconfig build with such a check, and nothing tripped. Signed-off-by: -
George Spelvin authored
Finally, the first use of previous two patches: eliminate the separate ad-hoc string hash functions in the sunrpc code. Now hash_str() is a wrapper around hash_string(), and hash_mem() is likewise a wrapper around full_name_hash(). Note that sunrpc code *does* call hash_mem() with a zero length, which is why the previous patch needed to handle that in full_name_hash(). (Thanks, Bruce, for finding that!) This also eliminates the only caller of hash_long which asks for more than 32 bits of output. The comment about the quality of hashlen_string() and full_name_hash() is jumping the gun by a few patches; they aren't very impressive now, but will be improved greatly later in the series. Signed-off-by:
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George Spelvin authored
We'd like to make more use of the highly-optimized dcache hash functions throughout the kernel, rather than have every subsystem create its own, and a function that hashes basic null-terminated strings is required for that. (The name is to emphasize that it returns both hash and length.) It's actually useful in the dcache itself, specifically d_alloc_name(). Other uses in the next patch. full_name_hash() is also tweaked to make it more generally useful: 1) Take a "char *" rather than "unsigned char *" argument, to be consistent with hash_name(). 2) Handle zero-length inputs. If we want more callers, we don't want to make them worry about corner cases. Signed-off-by:
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