- 22 Feb, 2013 40 commits
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Darrick J. Wong authored
Create a helper function to check if a backing device requires stable page writes and, if so, performs the necessary wait. Then, make it so that all points in the memory manager that handle making pages writable use the helper function. This should provide stable page write support to most filesystems, while eliminating unnecessary waiting for devices that don't require the feature. Before this patchset, all filesystems would block, regardless of whether or not it was necessary. ext3 would wait, but still generate occasional checksum errors. The network filesystems were left to do their own thing, so they'd wait too. After this patchset, all the disk filesystems except ext3 and btrfs will wait only if the hardware requires it. ext3 (if necessary) snapshots pages instead of blocking, and btrfs provides its own bdi so the mm will never wait. Network filesystems haven't been touched, so either they provide their own stable page guarantees or they don't block at all. The blocking behavior is back to what it was before 3.0 if you don't have a disk requiring stable page writes. Here's the result of using dbench to test latency on ext2: 3.8.0-rc3: Operation Count AvgLat MaxLat ---------------------------------------- WriteX 109347 0.028 59.817 ReadX 347180 0.004 3.391 Flush 15514 29.828 287.283 Throughput 57.429 MB/sec 4 clients 4 procs max_latency=287.290 ms 3.8.0-rc3 + patches: WriteX 105556 0.029 4.273 ReadX 335004 0.005 4.112 Flush 14982 30.540 298.634 Throughput 55.4496 MB/sec 4 clients 4 procs max_latency=298.650 ms As you can see, the maximum write latency drops considerably with this patch enabled. The other filesystems (ext3/ext4/xfs/btrfs) behave similarly, but see the cover letter for those results. Signed-off-by:
Darrick J. Wong <darrick.wong@oracle.com> Acked-by:
Steven Whitehouse <swhiteho@redhat.com> Reviewed-by:
Jan Kara <jack@suse.cz> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Ron Minnich <rminnich@sandia.gov> Cc: Latchesar Ionkov <lucho@ionkov.net> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Darrick J. Wong authored
This patchset ("stable page writes, part 2") makes some key modifications to the original 'stable page writes' patchset. First, it provides creators (devices and filesystems) of a backing_dev_info a flag that declares whether or not it is necessary to ensure that page contents cannot change during writeout. It is no longer assumed that this is true of all devices (which was never true anyway). Second, the flag is used to relaxed the wait_on_page_writeback calls so that wait only occurs if the device needs it. Third, it fixes up the remaining disk-backed filesystems to use this improved conditional-wait logic to provide stable page writes on those filesystems. It is hoped that (for people not using checksumming devices, anyway) this patchset will give back unnecessary performance decreases since the original stable page write patchset went into 3.0. Sorry about not fixing it sooner. Complaints were registered by several people about the long write latencies introduced by the original stable page write patchset. Generally speaking, the kernel ought to allocate as little extra memory as possible to facilitate writeout, but for people who simply cannot wait, a second page stability strategy is (re)introduced: snapshotting page contents. The waiting behavior is still the default strategy; to enable page snapshotting, a superblock flag (MS_SNAP_STABLE) must be set. This flag is used to bandaid^Henable stable page writeback on ext3[1], and is not used anywhere else. Given that there are already a few storage devices and network FSes that have rolled their own page stability wait/page snapshot code, it would be nice to move towards consolidating all of these. It seems possible that iscsi and raid5 may wish to use the new stable page write support to enable zero-copy writeout. Thank you to Jan Kara for helping fix a couple more filesystems. Per Andrew Morton's request, here are the result of using dbench to measure latencies on ext2: 3.8.0-rc3: Operation Count AvgLat MaxLat ---------------------------------------- WriteX 109347 0.028 59.817 ReadX 347180 0.004 3.391 Flush 15514 29.828 287.283 Throughput 57.429 MB/sec 4 clients 4 procs max_latency=287.290 ms 3.8.0-rc3 + patches: WriteX 105556 0.029 4.273 ReadX 335004 0.005 4.112 Flush 14982 30.540 298.634 Throughput 55.4496 MB/sec 4 clients 4 procs max_latency=298.650 ms As you can see, for ext2 the maximum write latency decreases from ~60ms on a laptop hard disk to ~4ms. I'm not sure why the flush latencies increase, though I suspect that being able to dirty pages faster gives the flusher more work to do. On ext4, the average write latency decreases as well as all the maximum latencies: 3.8.0-rc3: WriteX 85624 0.152 33.078 ReadX 272090 0.010 61.210 Flush 12129 36.219 168.260 Throughput 44.8618 MB/sec 4 clients 4 procs max_latency=168.276 ms 3.8.0-rc3 + patches: WriteX 86082 0.141 30.928 ReadX 273358 0.010 36.124 Flush 12214 34.800 165.689 Throughput 44.9941 MB/sec 4 clients 4 procs max_latency=165.722 ms XFS seems to exhibit similar latency improvements as ext2: 3.8.0-rc3: WriteX 125739 0.028 104.343 ReadX 399070 0.005 4.115 Flush 17851 25.004 131.390 Throughput 66.0024 MB/sec 4 clients 4 procs max_latency=131.406 ms 3.8.0-rc3 + patches: WriteX 123529 0.028 6.299 ReadX 392434 0.005 4.287 Flush 17549 25.120 188.687 Throughput 64.9113 MB/sec 4 clients 4 procs max_latency=188.704 ms ...and btrfs, just to round things out, also shows some latency decreases: 3.8.0-rc3: WriteX 67122 0.083 82.355 ReadX 212719 0.005 2.828 Flush 9547 47.561 147.418 Throughput 35.3391 MB/sec 4 clients 4 procs max_latency=147.433 ms 3.8.0-rc3 + patches: WriteX 64898 0.101 71.631 ReadX 206673 0.005 7.123 Flush 9190 47.963 219.034 Throughput 34.0795 MB/sec 4 clients 4 procs max_latency=219.044 ms Before this patchset, all filesystems would block, regardless of whether or not it was necessary. ext3 would wait, but still generate occasional checksum errors. The network filesystems were left to do their own thing, so they'd wait too. After this patchset, all the disk filesystems except ext3 and btrfs will wait only if the hardware requires it. ext3 (if necessary) snapshots pages instead of blocking, and btrfs provides its own bdi so the mm will never wait. Network filesystems haven't been touched, so either they provide their own wait code, or they don't block at all. The blocking behavior is back to what it was before 3.0 if you don't have a disk requiring stable page writes. This patchset has been tested on 3.8.0-rc3 on x64 with ext3, ext4, and xfs. I've spot-checked 3.8.0-rc4 and seem to be getting the same results as -rc3. [1] The alternative fixes to ext3 include fixing the locking order and page bit handling like we did for ext4 (but then why not just use ext4?), or setting PG_writeback so early that ext3 becomes extremely slow. I tried that, but the number of write()s I could initiate dropped by nearly an order of magnitude. That was a bit much even for the author of the stable page series! :) This patch: Creates a per-backing-device flag that tracks whether or not pages must be held immutable during writeout. Eventually it will be used to waive wait_for_page_writeback() if nothing requires stable pages. Signed-off-by: -
Johannes Berg authored
I recently made the mistake of writing: foo = lockdep_dereference_protected(..., lockdep_assert_held(...)); which is clearly bogus. If lockdep is disabled in the config this would cause a compile failure, if it is enabled then it compiles and causes a puzzling warning about dereferencing without the correct protection. Wrap the macro in "do { ... } while (0)" to also fail compile for this when lockdep is enabled. Signed-off-by:Johannes Berg <johannes.berg@intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by:
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Junxiao Bi authored
If lockres refresh failed, the super lock will never be released which will cause some processes on other cluster nodes hung forever. Signed-off-by:
Junxiao Bi <junxiao.bi@oracle.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Mark Fasheh <mfasheh@suse.com> Cc: <stable@vger.kernel.org> Signed-off-by:
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Tim Gardner authored
smatch analysis indicates a number of redundant NULL checks before calling kfree(), eg: fs/ocfs2/alloc.c:6138 ocfs2_begin_truncate_log_recovery() info: redundant null check on *tl_copy calling kfree() fs/ocfs2/alloc.c:6755 ocfs2_zero_range_for_truncate() info: redundant null check on pages calling kfree() etc.... [akpm@linux-foundation.org: revert dubious change in ocfs2_begin_truncate_log_recovery()] Signed-off-by:
Tim Gardner <tim.gardner@canonical.com> Cc: Mark Fasheh <mfasheh@suse.com> Acked-by:
Joel Becker <jlbec@evilplan.org> Signed-off-by:
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Wei Yongjun authored
The dereference should be moved below the NULL test. spatch with a semantic match is used to found this. (http://coccinelle.lip6.fr/) Signed-off-by:
Wei Yongjun <yongjun_wei@trendmicro.com.cn> Cc: Joel Becker <jlbec@evilplan.org> Signed-off-by:
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Kirill Tkhai authored
- Add magic for declarations of variables of popular kernel type like spinlock_t, list_head, wait_queue_head_t and other. - Add a set of specially handled declaration extentions like __attribute, __aligned and other. - Simplify pci_bus_* magic Signed-off-by:
Kirill V Tkhai <tkhai@yandex.ru> Cc: Michal Marek <mmarek@suse.cz> Signed-off-by:
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Greg Kroah-Hartman authored
How is the compiler even handling exported functions that are marked inline? Anyway, these shouldn't be inline because of that, so remove that marking. Based on a larger patch by Mark Charlebois to get LLVM to build the kernel. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Mark Charlebois <mcharleb@qualcomm.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: hank <pyu@redhat.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:
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Fabio Estevam authored
Fix the following sparse error: drivers/video/mx3fb.c:1309:28: warning: Using plain integer as NULL pointer Signed-off-by:
Fabio Estevam <fabio.estevam@freescale.com> Acked-by:
Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by:
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Ajay Kumar authored
disable_irq() should be moved to exynos_dp_suspend(), because enable_irq() is called at exynos_dp_resume(). Signed-off-by:
Ajay Kumar <ajaykumar.rs@samsung.com> Signed-off-by:
Jingoo Han <jg1.han@samsung.com> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Signed-off-by:
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Jingoo Han authored
of_find_node_by_name() returns a node pointer with refcount incremented, use of_node_put() on it when done. of_find_node_by_name() will call of_node_put() against the node pass to from parameter, thus we also need to call of_node_get(from) before calling of_find_node_by_name(). Signed-off-by:
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Tomasz Figa authored
The correct value for VIDCON1_VSTATUS_FRONTPORCH is 3, not 0. Signed-off-by:
Tomasz Figa <t.figa@samsung.com> Signed-off-by:
Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by:
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Jingoo Han authored
Add the bit definitions for CSC EQ709 and EQ601. These definitons are used to control the CSC parameter such as equation 709 and equation 601. Signed-off-by:
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Jingoo Han authored
Remove unnecessary brackets and the duplicated VIDTCON2 definition. Also, header comment is modified, because EXYNOS series is supported and <mach/regs-fb.h> is not available. Signed-off-by:
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Jingoo Han authored
S3C_FB_MAX_WIN is already defined in 'plat-samsung/include/plat/fb.h'. So, this definition in 'include/video/samsung_fimd.h' should be removed to avoid the duplication. Signed-off-by:
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Jingoo Han authored
Use ARCH_ dependancy when using s3c-fb. S3C_DEV_FB, S5P_DEV_FIMD0 cannot be enabled on EXYNOS5. So, ARCH_ should be used as dependancy for s3c-fb. Signed-off-by:
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Sachin Kamat authored
devm_* APIs are device managed and make exit and cleanup code simpler. While at it also remove some unused labels and fix an error path. Signed-off-by:
Sachin Kamat <sachin.kamat@linaro.org> Acked-by:
Donghwa Lee <dh09.lee@samsung.com> Cc: Inki Dae <inki.dae@samsung.com> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Signed-off-by:
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Sachin Kamat authored
Checking an unsigned variable for negative value returns false. Hence use the macro to fix it. Fixes the following smatch warning: drivers/video/exynos/exynos_mipi_dsi.c:417 exynos_mipi_dsi_probe() warn: unsigned 'dsim->irq' is never less than zero. Signed-off-by:
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Sachin Kamat authored
devm_* APIs are device managed and make error handling and code cleanup simpler. Signed-off-by:
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Fabio Estevam authored
FB_IMX is the framebuffer driver used by MX1, MX21, MX25 and MX27 processors. Pass this information to the Kconfig text to make it clear. Signed-off-by:
Sascha Hauer <s.hauer@pengutronix.de> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Signed-off-by:
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Zhou Zhu authored
Add display and fb support in pxa910 defconfig. Add tpohvga panel, spi support. Add logo support. Signed-off-by:
Zhou Zhu <zzhu3@marvell.com> Acked-by:
Haojian Zhuang <haojian.zhuang@gmail.com> Cc: Lisa Du <cldu@marvell.com> Cc: Guoqing Li <ligq@marvell.com> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Signed-off-by:
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Zhou Zhu authored
Enable display in ttc_dkb. Signed-off-by:
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Zhou Zhu authored
Add device for display controller and fb support Signed-off-by:
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Zhou Zhu authored
Add spi port support in mmp display controller. This port is from display controller and for panel usage. This driver implemented and registered as a spi master. Signed-off-by:
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Lisa Du authored
Add tpo hvga panel support in marvell display framework. This panel driver implements modes query and power on/off. This panel driver gets panel config/ plat power on/off/ connected path name from machine-info and registered as a spi device. This panel driver uses mmp_disp supplied register_panel function to register panel to path as machine-info defined. Signed-off-by:
Lisa Du <cldu@marvell.com> Signed-off-by:
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Guoqing Li authored
Marvell mmp series display controller support in mmpdisp subsystem. This driver focus on implementation of hardware operations of path/overlay, which is defined in mmp display subsystem interface. This driver registers all pathes to mmp display framework. Signed-off-by:
Guoqing Li <ligq@marvell.com> Signed-off-by:
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Arnd Bergmann authored
Commit 16559ae4 ("kgdb: remove #include <linux/serial_8250.h> from kgdb.h") changes the kgdb.h file so that drivers including it do not implicitly include linux/platform_device.h. The mmp framebuffer driver is new, so Greg did not have a chance to fix it up when introducing his change. Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Cc: Zhou Zhu <zzhu3@marvell.com> Cc: Lisa Du <cldu@marvell.com> Cc: Guoqing Li <ligq@marvell.com> Acked-by:
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Zhou Zhu authored
Add fb support for Marvell mmp display subsystem. This driver is configured using "buffer driver mach info". With configured name of path, this driver get path using using exported interface of mmp display driver. Then this driver get overlay using configured id and operates on this overlay to show buffers on display devices. Signed-off-by:
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Zhou Zhu authored
Add mmp display subsystem to support Marvell MMP display controllers. This subsystem contains 4 parts: --fb folder --core.c --hw folder --panel folder 1. fb folder contains implementation of fb. fb get path and overlay from common interface and operates on these structures. 2. core.c provides common interface for a hardware abstraction. Major parts of this interface are: a) Path: path is a output device connected to a panel or HDMI TV. Main operations of the path is set/get timing/output color. fb operates output device through path structure. b) Ovly: Ovly is a buffer shown on the path. Ovly describes frame buffer and its source/destination size, offset, input color, buffer address, z-order, and so on. Each fb device maps to one overlay. 3. hw folder contains implementation of hardware operations defined by core.c. It registers paths for fb use. 4. panel folder contains implementation of panels. It's connected to path. Panel drivers would also regiester panels and linked to path when probe. Signed-off-by: -
Arve Hjønnevåg authored
Framebuffer support for the Goldfish emulator. This takes the Google emulator and applies the x86 cleanups as well as moving the blank methods to the usual Linux place and dropping the Android early suspend logic (for now at least, that can be looked at as Android and upstream converge). Dropped various oddities like setting MTRRs on a virtual frame buffer emulation... With the drivers so far you can now boot a Linux initrd and have fun. [sheng@linux.intel.com: cleaned up to handle x86] [thomas.keel@intel.com: ported to 3.4] [alan@linux.intel.com: cleaned up for style and 3.7, moved blank methods] [akpm@linux-foundation.org: fix (silly) sparse warnings] Signed-off-by:
Mike A. Chan <mikechan@google.com> Signed-off-by:
Arve Hjønnevåg <arve@android.com> Signed-off-by:
Sheng Yang <sheng@linux.intel.com> Signed-off-by:
Yunhong Jiang <yunhong.jiang@intel.com> Signed-off-by:
Xiaohui Xin <xiaohui.xin@intel.com> Signed-off-by:
Jun Nakajima <jun.nakajima@intel.com> Signed-off-by:
Bruce Beare <bruce.j.beare@intel.com> Signed-off-by:
Tom Keel <thomas.keel@intel.com> Signed-off-by:
Alan Cox <alan@linux.intel.com> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> Signed-off-by:
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Kamal Mostafa authored
Explicitly clear_margins when clearing the logo, in case the font dimensions are non-integral to the framebuffer dimensions. Signed-off-by:
Kamal Mostafa <kamal@whence.com> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> Signed-off-by:
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Christian Lamparter authored
Move the device rebind procedures for cardbus devices from the pm.resume into the pm.complete callback. The reason for moving the code is: "[...] The PM code needs to send suspend and resume messages to every device in the right order, and it can't do that if new devices are being added at the same time. [...]" However the situation really isn't quite that rigid. In particular, adding new children during a resume callback shouldn't cause much of problem because the children don't need to be resumed anyway (since they were never suspended). On the other hand, if you do it you will get a dev_warn() from the PM core, something like 'parent should not be sleeping'. Still, it is considered bad form and should be avoided if possible." (Alan Stern's full comment about the topic can be found here: <https://lkml.org/lkml/2012/7/10/254>) Signed-off-by:
Christian Lamparter <chunkeey@googlemail.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Greg KH <greg@kroah.com> Acked-by:
"Rafael J. Wysocki" <rjw@sisk.pl> Signed-off-by:
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Geert Uytterhoeven authored
On cris-linux-gcc, __SIZE_TYPE__ expands to "unsigned int", as gcc-4.6.3-nolibc/cris-linux/lib/gcc/cris-linux/4.6.3/plugin/include/config/cris/linux.h has #define SIZE_TYPE "unsigned int" Hence __kernel_size_t is also "unsigned int". But __kernel_ssize_t is "long", which has a different base type, causing compiler warnings like: fs/quota/quota_tree.c:372:4: warning: format '%zd' expects argument of type 'signed size_t', but argument 4 has type 'ssize_t' [-Wformat] To fix this, __kernel_ssize_t should be changed to "int". Hence cris can just use the generic 32-bit versions from include/asm-generic/posix_types.h for all size-related types. Signed-off-by:Geert Uytterhoeven <geert@linux-m68k.org> Cc: Mikael Starvik <starvik@axis.com> Acked-by:
Jesper Nilsson <jesper.nilsson@axis.com> Cc: Hans-Peter Nilsson <hans-peter.nilsson@axis.com> Signed-off-by:
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Wei Yongjun authored
Signed-off-by:
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MITSUNARI Shigeo authored
We found that bdev->bd_invalidated was left set once revalidate_disk() is called, which results in page cache flush every time that device is open. Specifically, we found this problem in MD block device. Once we resize a MD device, mdadm --monitor periodically flush all page cache for that device every 60 or 1000 seconds when it opens the device. This bug lies since at least 3.2.0 till the latest kernel(3.6.2). Patch is attached. The following steps will reproduce the problem. 1. prepair a block device (eg /dev/sdb). 2. create two partitions: sudo parted /dev/sdb mklabel gpt mkpart primary 0% 50% mkpart primary 50% 100% 3. create a md device. sudo mdadm -C /dev/md/hoge -l 1 -n 2 -e 1.2 --assume-clean --auto=md --symlink=no /dev/sdb1 /dev/sdb2 4. create file system and mount it sudo mkfs.ext3 /dev/md/hoge sudo mkdir /mnt/test sudo mount /dev/md/hoge /mnt/test 5. try to resize the device sudo mdadm -G /dev/md/hoge --size=max 6. create a file to fill file cache. sudo dd if=/dev/urandom of=/mnt/test/data bs=1M count=10 and verify the current status of file by free command. 7. mdadm monitor will open the md device every 1000 seconds and you will find all file cache on the device are cleared. The timing can be reduced by the following steps. a) kill mdadm and restart it with --delay option /sbin/mdadm --monitor --delay=30 --pid-file /var/run/mdadm/monitor.pid --daemonise --scan --syslog or open the md device directly. sudo dd if=/dev/md/hoge of=/dev/null bs=4096 count=1 Signed-off-by:
MITSUNARI Shigeo <herumi@nifty.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by:
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Jim Somerville authored
Running the command: inotifywait -e unmount /mnt/disk immediately aborts with a -EINVAL return code. This is however a valid parameter. This abort occurs only if unmount is the sole event parameter. If other event parameters are supplied, then the unmount event wait will work. The problem was introduced by commit 44b350fc ("inotify: Fix mask checks"). In that commit, it states: The mask checks in inotify_update_existing_watch() and inotify_new_watch() are useless because inotify_arg_to_mask() sets FS_IN_IGNORED and FS_EVENT_ON_CHILD bits anyway. But instead of removing the useless checks, it did this: mask = inotify_arg_to_mask(arg); - if (unlikely(!mask)) + if (unlikely(!(mask & IN_ALL_EVENTS))) return -EINVAL; The problem is that IN_ALL_EVENTS doesn't include IN_UNMOUNT, and other parts of the code keep IN_UNMOUNT separate from IN_ALL_EVENTS. So the check should be: if (unlikely(!(mask & (IN_ALL_EVENTS | IN_UNMOUNT)))) But inotify_arg_to_mask(arg) always sets the IN_UNMOUNT bit in the mask anyway, so the check is always going to pass and thus should simply be removed. Also note that inotify_arg_to_mask completely controls what mask bits get set from arg, there's no way for invalid bits to get enabled there. Lets fix it by simply removing the useless broken checks. Signed-off-by:
Jim Somerville <Jim.Somerville@windriver.com> Signed-off-by:
Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: John McCutchan <john@johnmccutchan.com> Cc: Robert Love <rlove@rlove.org> Cc: Eric Paris <eparis@parisplace.org> Cc: <stable@vger.kernel.org> [2.6.37+] Signed-off-by:
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Dan Carpenter authored
The copy_to_user() call returns the number of bytes remaining but we want to return -EFAULT on error. Fixes "x32: fix waitid()" Signed-off-by:
Dan Carpenter <dan.carpenter@oracle.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by:
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Daniel Santos authored
Introduce compiletime_assert to compiler.h, which moves the details of how to break a build and emit an error message for a specific compiler to the headers where these details should be. Following in the tradition of the POSIX assert macro, compiletime_assert creates a build-time error when the supplied condition is *false*. Next, we add BUILD_BUG_ON_MSG to bug.h which simply wraps compiletime_assert, inverting the logic, so that it fails when the condition is *true*, consistent with the language "build bug on." This macro allows you to specify the error message you want emitted when the supplied condition is true. Finally, we remove all other code from bug.h that mucks with these details (BUILD_BUG & BUILD_BUG_ON), and have them all call BUILD_BUG_ON_MSG. This not only reduces source code bloat, but also prevents the possibility of code being changed for one macro and not for the other (which was previously the case for BUILD_BUG and BUILD_BUG_ON). Since __compiletime_error_fallback is now only used in compiler.h, I'm considering it a private macro and removing the double negation that's now extraneous. [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by:
Daniel Santos <daniel.santos@pobox.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by:
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Daniel Santos authored
Prior to the introduction of __attribute__((error("msg"))) in gcc 4.3, creating compile-time errors required a little trickery. BUILD_BUG{,_ON} uses this attribute when available to generate compile-time errors, but also uses the negative-sized array trick for older compilers, resulting in two error messages in some cases. The reason it's "some" cases is that as of gcc 4.4, the negative-sized array will not create an error in some situations, like inline functions. This patch replaces the negative-sized array code with the new __compiletime_error_fallback() macro which expands to the same thing unless the the error attribute is available, in which case it expands to do{}while(0), resulting in exactly one compile-time error on all versions of gcc. Note that we are not changing the negative-sized array code for the unoptimized version of BUILD_BUG_ON, since it has the potential to catch problems that would be disabled in later versions of gcc were __compiletime_error_fallback used. The reason is that that an unoptimized build can't always remove calls to an error-attributed function call (like we are using) that should effectively become dead code if it were optimized. However, using a negative-sized array with a similar value will not result in an false-positive (error). The only caveat being that it will also fail to catch valid conditions, which we should be expecting in an unoptimized build anyway. Signed-off-by: -
Daniel Santos authored
Negative sized arrays wont create a compile-time error in some cases starting with gcc 4.4 (e.g., inlined functions), but gcc 4.3 introduced the error function attribute that will. This patch modifies BUILD_BUG_ON to behave like BUILD_BUG already does, using the error function attribute so that you don't have to build the entire kernel to discover that you have a problem, and then enjoy trying to track it down from a link-time error. Also, we are only including asm/bug.h and then expecting that linux/compiler.h will eventually be included to define __linktime_error (used in BUILD_BUG_ON). This patch includes it directly for clarity and to avoid the possibility of changes in <arch>/*/include/asm/bug.h being changed or not including linux/compiler.h for some reason. Signed-off-by:
Borislav Petkov <bp@alien8.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: David Rientjes <rientjes@google.com> Cc: Joe Perches <joe@perches.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by:
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