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2012-05-12i2c: tegra: fix 10bit address configurationLaxman Dewangan
The slave address of device to be configured in packet header as follows: 7 bit address: PacketHeader3[7:1] 10 bit address: PacketHeader3[9:0] Fixing the code to make packet header3 properly. Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com> Acked-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: muxes: rename first set of drivers to a standard patternWolfram Sang
Apply a naming pattern like in the rest of the subsystem to a first set of mux drivers. Those drivers are the low-hanging fruit; we want to pick them to motivate upcoming drivers to follow the new pattern. The missing GPIO driver will be converted in a later patch. Signed-off-by: Wolfram Sang <w.sang@pengutronix.de> Acked-by: Guenter Roeck <guenter.roeck@ericsson.com> (pca9541) Acked-by: Jean Delvare <khali@linux-fr.org>
2012-05-12of/i2c: implement of_find_i2c_adapter_by_nodeStephen Warren
This finds the struct i2c_adapter * for a given device tree node. Just like of_find_i2c_device_by_node. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: implement i2c_verify_adapterStephen Warren
This converts a struct device * to a struct i2c_adapter * while verifying that the device really is an I2C adapter. Just like i2c_verify_client. Signed-off-by: Stephen Warren <swarren@nvidia.com> Acked-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-s3c2410: Add HDMIPHY quirk for S3C2440Karol Lewandowski
This patch adds support for s3c2440 I2C bus controller dedicated HDMIPHY device on Exynos4 platform. Some quirks are introduced due to differences between HDMIPHY and other I2C controllers on Exynos4. These differences are: - no GPIOs, HDMIPHY is inside the SoC and the controller is connected internally - due to unknown reason (probably HW bug in HDMIPHY and/or the controller) a transfer fails to finish. The controller hangs after sending the last byte, the workaround for this bug is resetting the controller after each transfer Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com> Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com> Tested-by: Tomasz Stanislawski <t.stanislaws@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-s3c2410: Rework device type handlingKarol Lewandowski
Reorganize driver a bit to better handle device tree-based systems: - move machine type to driver's private structure instead of quering platform device variants in runtime - replace s3c24xx_i2c_type enum with unsigned int that holds bitmask with revision-specific quirks Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: muxes are not EXPERIMENTAL anymoreWolfram Sang
We got multiple patches to add mux support to device tree, so people are using it happily already and build up on it. I also used it in a project without encountering problems. 20 months of EXPERIMENTAL should do for this. Signed-off-by: Wolfram Sang <w.sang@pengutronix.de> Acked-by: Peter Korsgaard <jacmet@sunsite.dk> Acked-by: Guenter Roeck <guenter.roeck@ericsson.com> Acked-by: Jean Delvare <khali@linux-fr.org> Acked-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Michael Lawnick <ml.lawnick@gmx.de> Cc: Lars-Peter Clausen <lars@metafoo.de> Cc: David Daney <ddaney.cavm@gmail.com>
2012-05-12i2c/of: Automatically populate i2c mux busses from device tree data.David Daney
For 'normal' i2c bus drivers, we can call of_i2c_register_devices() and have the device tree framework automatically populate the bus with the devices specified in the device tree. This patch adds a common code to the i2c mux framework to have the mux sub-busses be populated by the of_i2c_register_devices() too. If the mux device has an of_node, we populate the sub-bus' of_node so that the subsequent call to of_i2c_register_devices() will find the corresponding devices. It seemed better to put this logic in i2c_add_mux_adapter() rather than the individual mux drivers, as they will all probably want to do the same thing. Signed-off-by: David Daney <david.daney@cavium.com> Acked-by: Stephen Warren <swarren@wwwdotorg.org> Tested-by: Lars-Peter Clausen <lars@metafoo.de> [wsa: removed superfluous ret-variable and fixed a typo in a comment] Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: Add a struct device * parameter to i2c_add_mux_adapter()David Daney
And adjust all callers. The new device parameter is used in the next patch to initialize the mux's of_node so that its children may be automatically populated. Signed-off-by: David Daney <david.daney@cavium.com> Tested-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12of/i2c: call i2c_verify_client from of_find_i2c_device_by_nodeStephen Warren
i2c_bus_type may contain both I2C clients and I2C adapters. Fix of_find_i2c_device_by_node to call i2c_verify_client to ensure that it only returns non-NULL of I2C clients. Signed-off-by: Stephen Warren <swarren@nvidia.com> Acked-by: Rob Herring <rob.herring@calxeda.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: designware: Add clk_{un}prepare() supportViresh Kumar
clk_{un}prepare is mandatory for platforms using common clock framework. Since this driver is used by SPEAr platform, which supports common clock framework, add clk_{un}prepare() support for designware i2c. Signed-off-by: Viresh Kumar <viresh.kumar@st.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: designware: add PM supportDeepak Sikri
This patch adds in support for standby/S2R/hybernate for i2c-designware driver. Signed-off-by: Deepak Sikri <deepak.sikri@st.com> Signed-off-by: Rajeev Kumar <rajeev-dlh.kumar@st.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: ixp2000: remove driverRob Herring
The platform is removed, so there are no users of this driver. Signed-off-by: Rob Herring <rob.herring@calxeda.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: pnx: add device tree supportRoland Stigge
This patch adds device tree support to the pnx-i2c driver by using platform resources for memory region and irq and removing dependency on mach includes. The following platforms are affected: * PNX * LPC31xx (WIP) * LPC32xx The patch is based on a patch by Jon Smirl, working on lpc31xx integration Signed-off-by: Roland Stigge <stigge@antcom.de> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: imx: don't use strcpy but strlcpyWolfram Sang
Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>
2012-05-12i2c: eg20t: don't use strcpy but strlcpyWolfram Sang
Signed-off-by: Wolfram Sang <wolfram@the-dreams.de> Cc: Tomoya MORINAGA <tomoya.rohm@gmail.com>
2012-05-12i2c: eg20t: remove unused functionWolfram Sang
cppcheck rightfully says: drivers/i2c/busses/i2c-eg20t.c:266: style: The function 'ktime_lt' is never used Signed-off-by: Wolfram Sang <wolfram@the-dreams.de> Cc: Tomoya MORINAGA <tomoya.rohm@gmail.com>
2012-05-12i2c: eg20t: pass on return value in i2c_xferWolfram Sang
smatch says: drivers/i2c/busses/i2c-eg20t.c:702 pch_i2c_xfer() info: why not propagate 'ret' from mutex_lock_interruptible() instead of -512? which is especially true since for -ENORESTARTSYS it is said in linux/errno.h "signal_pending() MUST be set" which is not done here. So just pass on the return value we got. Signed-off-by: Wolfram Sang <wolfram@the-dreams.de> Cc: Tomoya MORINAGA <tomoya.rohm@gmail.com>
2012-05-12i2c: eg20t: use NULL instead of 0Wolfram Sang
sparse rightfully says: drivers/i2c/busses/i2c-eg20t.c:990:59: warning: Using plain integer as NULL pointer Signed-off-by: Wolfram Sang <wolfram@the-dreams.de> Cc: Tomoya MORINAGA <tomoya.rohm@gmail.com>
2012-05-12i2c-eg20t: Merge two functionsTomoya MORINAGA
By previous patch, pch_i2c_wait_for_xfer_complete can be merged to pch_i2c_wait_for_check_xfer. Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-eg20t: add helper function for xfer checkTomoya MORINAGA
Currently, there are the same code for xfer complete check processing. So, I add helper function pch_i2c_wait_for_check_xfer. Reported-by: Wolfram Sang <w.sang@pengutronix.de> Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-eg20t: Call init() when wait-event timeout occursTomoya MORINAGA
Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-mpc: avoid I2C abnormal after resuming from deep sleepZhao Chenhui
When entering deep sleep, the value in the registers I2CFDR and I2CDFSRR are lost. This causes I2C access to fail after resuming. Add suspend/resume routines to save/restore the registers I2CFDR and I2CDFSRR. Signed-off-by: Zhao Chenhui <chenhui.zhao@freescale.com> Signed-off-by: Li Yang <leoli@freescale.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: sh_mobile: add device tree supportMagnus Damm
This patch enables DT support for the IIC driver used on SH-based SoCs such as sh7722 and sh7724 among others as well as SH-Mobile SoCs such as sh7367, sh7377, sh7372, sh73a0 and r8a7740. Tested with out-of-tree DT support code on the sh7372 Mackerel board. Signed-off-by: Magnus Damm <damm@opensource.se> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-pnx.c: Remove duplicated i2c.hRoland Stigge
The platforms using i2c-pnx.c both defined a duplicated i2c.h (used nowhere else). This patch removes those and integrates the contents into the driver itself. Signed-off-by: Roland Stigge <stigge@antcom.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-pnx.c: Use resources in platformsRoland Stigge
As a precondition for device tree conversion, the platforms using i2c-pnx.c are converted to using mem and irq resources instead of platform data. Signed-off-by: Roland Stigge <stigge@antcom.de> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: designware: Add support for 16bit register accessStefan Roese
The STM SPEAr platform can only access the i2c controller register via 16bit read/write functions. This patch adds support to automatically detect this 16bit access mode. Signed-off-by: Stefan Roese <sr@denx.de> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c: Dynamically assign adapter id if it wasn't explictly specifiedKarol Lewandowski
Commit 488bf314b ("i2c: Allow i2c_add_numbered_adapter() to assign a bus id") reworked i2c_add_numbered_adapter() to call i2c_add_adapter() if requested bus was -1. This allows to simplify driver's initialization procedure by using just one function for static and dynamic adapter id registration. This patch updates few more drivers (missed out in original patch) to use this functionality. Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-pxa: Drop leftover commentKarol Lewandowski
Commit 488bf314b ("i2c: Allow i2c_add_numbered_adapter() to assign a bus id") reworked i2c-pxa driver leaving obsolete comment. This commit simply drops it. Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-12i2c-s3c2410: Drop unused defineKarol Lewandowski
Use standard of_match_ptr() to avoid defining variable unused in non device tree builds. Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Acked-by: Grant Likely <grant.likely@secretlab.ca> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-05-06Linux 3.4-rc6v3.4-rc6Linus Torvalds
2012-05-06Merge branch 'x86-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 fixes form Peter Anvin * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: intel_mid_powerbtn: mark irq as IRQF_NO_SUSPEND arch/x86/platform/geode/net5501.c: change active_low to 0 for LED driver x86, relocs: Remove an unused variable asm-generic: Use __BITS_PER_LONG in statfs.h x86/amd: Re-enable CPU topology extensions in case BIOS has disabled it
2012-05-06Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs Pull btrfs fixes from Chris Mason: "The big ones here are a memory leak we introduced in rc1, and a scheduling while atomic if the transid on disk doesn't match the transid we expected. This happens for corrupt blocks, or out of date disks. It also fixes up the ioctl definition for our ioctl to resolve logical inode numbers. The __u32 was a merging error and doesn't match what we ship in the progs." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: Btrfs: avoid sleeping in verify_parent_transid while atomic Btrfs: fix crash in scrub repair code when device is missing btrfs: Fix mismatching struct members in ioctl.h Btrfs: fix page leak when allocing extent buffers Btrfs: Add properly locking around add_root_to_dirty_list
2012-05-06x86: fix broken TASK_SIZE for ia32_aoutAl Viro
Setting TIF_IA32 in load_aout_binary() used to be enough; these days TASK_SIZE is controlled by TIF_ADDR32 and that one doesn't get set there. Switch to use of set_personality_ia32()... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-06Btrfs: avoid sleeping in verify_parent_transid while atomicChris Mason
verify_parent_transid needs to lock the extent range to make sure no IO is underway, and so it can safely clear the uptodate bits if our checks fail. But, a few callers are using it with spinlocks held. Most of the time, the generation numbers are going to match, and we don't want to switch to a blocking lock just for the error case. This adds an atomic flag to verify_parent_transid, and changes it to return EAGAIN if it needs to block to properly verifiy things. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2012-05-05Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha Pull alpha fixes from Matt Turner: "My alpha tree is back up (after taking quite some time to get my GPG key signed). It contains just some simple fixes." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha: alpha: silence 'const' warning in sys_marvel.c alpha: include module.h to fix modpost on Tsunami alpha: properly define get/set_rtc_time on Marvel/SMP alpha: VGA_HOSE depends on VGA_CONSOLE
2012-05-05TTY: pdc_cons, fix regression in closeJiri Slaby
The test in pdc_console_tty_close '!tty->count' was always wrong because tty->count is decremented after tty->ops->close is called and thus can never be zero. Hence the 'then' branch was never executed and the timer never deleted. This did not matter until commit 5dd5bc40f3b6 ("TTY: pdc_cons, use tty_port"). There we needed to set TTY in tty_port to NULL, but this never happened due to the bug above. So change the test to really trigger at the last close by changing the condition to 'tty->count == 1'. Well, the driver should not touch tty->count at all. It should use tty_port->count and count open count there itself. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reported-and-tested-by: Mikulas Patocka <mpatocka@redhat.com> Cc: Kyle McMartin <kyle@mcmartin.ca> Cc: Helge Deller <deller@gmx.de> Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-05Merge tag 'sound-3.4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound Pull sound sound fixes from Takashi Iwai: "As good as nothing exciting here; just a few trivial fixes for various ASoC stuff." * tag 'sound-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound: ASoC: omap-pcm: Free dma buffers in case of error. ASoC: s3c2412-i2s: Fix dai registration ASoC: wm8350: Don't use locally allocated codec struct ASoC: tlv312aic23: unbreak resume ASoC: bf5xx-ssm2602: Set DAI format ASoC: core: check of_property_count_strings failure ASoC: dt: sgtl5000.txt: Add description for 'reg' field ASoC: wm_hubs: Make sure we don't disable differential line outputs
2012-05-05Merge branch 'release' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux Pull an ACPI patch from Len Brown: "It fixes a D3 issue new in 3.4-rc1." By Lin Ming via Len Brown: * 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux: ACPI: Fix D3hot v D3cold confusion
2012-05-05init: don't try mounting device as nfs root unless type fully matchesSasha Levin
Currently, we'll try mounting any device who's major device number is UNNAMED_MAJOR as NFS root. This would happen for non-NFS devices as well (such as 9p devices) but it wouldn't cause any issues since mounting the device as NFS would fail quickly and the code proceeded to doing the proper mount: [ 101.522716] VFS: Unable to mount root fs via NFS, trying floppy. [ 101.534499] VFS: Mounted root (9p filesystem) on device 0:18. Commit 6829a048102a ("NFS: Retry mounting NFSROOT") introduced retries when mounting NFS root, which means that now we don't immediately fail and instead it takes an additional 90+ seconds until we stop retrying, which has revealed the issue this patch fixes. This meant that it would take an additional 90 seconds to boot when we're not using a device type which gets detected in order before NFS. This patch modifies the NFS type check to require device type to be 'Root_NFS' instead of requiring the device to have an UNNAMED_MAJOR major. This makes boot process cleaner since we now won't go through the NFS mounting code at all when the device isn't an NFS root ("/dev/nfs"). Signed-off-by: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-05Merge branch 'fix/asoc' into for-linusTakashi Iwai
2012-05-05Merge branch 'for-3.4' of ↵Takashi Iwai
git://git.kernel.org/pub/scm/linux/kernel/git/lrg/asoc into fix/asoc
2012-05-05Merge tag 'asoc-3.4' of ↵Takashi Iwai
git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus ASoC: Updates for 3.4 Nothing terribly exciting here, a bunch of small and simple fixes scattered around the place.
2012-05-05ACPI: Fix D3hot v D3cold confusionLin Ming
Before this patch, ACPI_STATE_D3 incorrectly referenced D3hot in some places, but D3cold in other places. After this patch, ACPI_STATE_D3 always means ACPI_STATE_D3_COLD; and all references to D3hot use ACPI_STATE_D3_HOT. ACPI's _PR3 method is used to enter both D3hot and D3cold states. What distinguishes D3hot from D3cold is the presence _PR3 (Power Resources for D3hot) If these resources are all ON, then the state is D3hot. If _PR3 is not present, or all _PR0 resources for the devices are OFF, then the state is D3cold. This patch applies after Linux-3.4-rc1. A future syntax cleanup may remove ACPI_STATE_D3 to emphasize that it always means ACPI_STATE_D3_COLD. Signed-off-by: Lin Ming <ming.m.lin@intel.com> Acked-by: Rafael J. Wysocki <rjw@sisk.pl> Reviewed-by: Aaron Lu <aaron.lu@amd.com> Signed-off-by: Len Brown <len.brown@intel.com>
2012-05-04hfsplus: Fix potential buffer overflowsGreg Kroah-Hartman
Commit ec81aecb2966 ("hfs: fix a potential buffer overflow") fixed a few potential buffer overflows in the hfs filesystem. But as Timo Warns pointed out, these changes also need to be made on the hfsplus filesystem as well. Reported-by: Timo Warns <warns@pre-sense.de> Acked-by: WANG Cong <amwang@redhat.com> Cc: Alexey Khoroshilov <khoroshilov@ispras.ru> Cc: Miklos Szeredi <mszeredi@suse.cz> Cc: Sage Weil <sage@newdream.net> Cc: Eugene Teo <eteo@redhat.com> Cc: Roman Zippel <zippel@linux-m68k.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@lst.de> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Dave Anderson <anderson@redhat.com> Cc: stable <stable@vger.kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-04Merge branch 'timers-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer fix from Thomas Gleixner. * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: rtc: Fix possible null pointer dereference in rtc-mpc5121.c
2012-05-04Merge git://git.samba.org/sfrench/cifs-2.6Linus Torvalds
Pull CIFS fixes from Steve French. * git://git.samba.org/sfrench/cifs-2.6: fs/cifs: fix parsing of dfs referrals cifs: make sure we ignore the credentials= and cred= options [CIFS] Update cifs version to 1.78 cifs - check S_AUTOMOUNT in revalidate cifs: add missing initialization of server->req_lock cifs: don't cap ra_pages at the same level as default_backing_dev_info CIFS: Fix indentation in cifs_show_options
2012-05-04CPU frequency drivers MAINTAINERS updateDave Jones
Remove myself as cpufreq maintainer. x86 driver changes can go through the regular x86/ACPI trees. ARM driver changes through the ARM trees. cpufreq core changes are rare these days, and can just go to lkml/direct. Signed-off-by: Dave Jones <davej@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-04seqlock: add 'raw_seqcount_begin()' functionLinus Torvalds
The normal read_seqcount_begin() function will wait for any current writers to exit their critical region by looping until the sequence count is even. That "wait for sequence count to stabilize" is the right thing to do if the read-locker will just retry the whole operation on contention: no point in doing a potentially expensive reader sequence if we know at the beginning that we'll just end up re-doing it all. HOWEVER. Some users don't actually retry the operation, but instead will abort and do the operation with proper locking. So the sequence count case may be the optimistic quick case, but in the presense of writers you may want to do full locking in order to guarantee forward progress. The prime example of this would be the RCU name lookup. And in that case, you may well be better off without the "retry early", and are in a rush to instead get to the failure handling. Thus this "raw" interface that just returns the sequence number without testing it - it just forces the low bit to zero so that read_seqcount_retry() will always fail such a "active concurrent writer" scenario. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-04Fix __read_seqcount_begin() to use ACCESS_ONCE for sequence value readLinus Torvalds
We really need to use a ACCESS_ONCE() on the sequence value read in __read_seqcount_begin(), because otherwise the compiler might end up reloading the value in between the test and the return of it. As a result, it might end up returning an odd value (which means that a write is in progress). If the reader is then fast enough that that odd value is still the current one when the read_seqcount_retry() is done, we might end up with a "successful" read sequence, even despite the concurrent write being active. In practice this probably never really happens - there just isn't anything else going on around the read of the sequence count, and the common case is that we end up having a read barrier immediately afterwards. So the code sequence in which gcc might decide to reaload from memory is small, and there's no reason to believe it would ever actually do the reload. But if the compiler ever were to decide to do so, it would be incredibly annoying to debug. Let's just make sure. Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>