After emulating an unaligned access in delay slot of a branch, we
pretend as the delay slot never happened - so return back to actual
branch target (or next PC if branch was not taken).
Curently we did this by handling STATUS32.DE, we also need to clear the
BTA.T bit, which is disregarded when returning from original misaligned
exception, but could cause weirdness if it took the interrupt return
path (in case interrupt was acive too)
One ARC700 customer ran into this when enabling unaligned access fixup
for kernel mode accesses as well
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This is needed on HS38 cores, for setting up IO-Coherency aperture properly
The polling could perturb the caches and coherecy fabric which could be
wrong in the small window when Master is setting up IOC aperture etc
in arc_cache_init()
We do it only for ARCv2 based builds to not affect EZChip ARCompact
based platform.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
For run-on-reset SMP configs, non master cores call a routine which
waits until Master gives it a "go" signal (currently using a shared
mem flag). The same routine then jumps off the well known entry point of
all non Master cores i.e. @first_lines_of_secondary
This patch moves out the last part into one single place in early boot
code.
This is better in terms of absraction (the wait API only waits) and
returns, leaving out the "jump off to" part.
In actual implementation this requires some restructuring of the early
boot code as well as Master now jumps to BSS setup explicitly,
vs. falling thru into it before.
Technically this patch doesn't cause any functional change, it just
moves the ugly #ifdef'ry from assembly code to "C"
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
commit 3c7c7a2fc8 ("ARC: Don't use "+l" inline asm constraint")
modified the inline assembly to setup LP_COUNT register manually and NOT
rely on gcc to do it (with the +l inline assembler contraint hint, now
being retired in the compiler)
However the fix was flawed as we didn't add LP_COUNT to asm clobber list,
meaning gcc doesn't know that LP_COUNT or zero-delay-loops are in action
in the inline asm.
This resulted in some fun - as nested ZOL loops were being generared
| mov lp_count,250000 ;16 # tmp235,
| lp .L__GCC__LP14 # <======= OUTER LOOP (gcc generated)
| .L14:
| ld r2, [r5] # MEM[(volatile u32 *)prephitmp_43], w
| dmb 1
| breq r2, -1, @.L21 #, w,,
| bbit0 r2,1,@.L13 # w,,
| ld r4,[r7] ;25 # loops_per_jiffy, loops_per_jiffy
| mpymu r3,r4,r6 #, loops_per_jiffy, tmp234
|
| mov lp_count, r3 # <====== INNER LOOP (from inline asm)
| lp 1f
| nop
| 1:
| nop_s
| .L__GCC__LP14: ; loop end, start is @.L14 #,
This caused issues with drivers relying on sane behaviour of udelay
friends.
With LP_COUNT added to clobber list, gcc doesn't generate the outer
loop in say above case.
Addresses STAR 9001146134
Reported-by: Joao Pinto <jpinto@synopsys.com>
Fixes: 3c7c7a2fc8 ("ARC: Don't use "+l" inline asm constraint")
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Ignore value of interrupt distribution mode for common interrupts in
IDU since setting of affinity using value from Device Tree is deprecated
in ARC. Originally it is done in idu_irq_xlate() function and it is
semantically wrong and does not guaranty that an affinity value will be
set properly. idu_irq_enable() function is better place for
initialization of common interrupts.
By default send all common interrupts to all available online CPUs.
The affinity of common interrupts in IDU must be set manually since
in some cases the kernel will not call irq_set_affinity() by itself:
1. When the kernel is not configured with support of SMP.
2. When the kernel is configured with support of SMP but upper
interrupt controllers does not support setting of the affinity
and cannot propagate it to IDU.
Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
The programming model has been fixed with prev patches so re-enable it
by default
This reverts commit 23cb1f6440.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
arc_cache_init() is called for each core so can't be tagged __init.
However bulk of it is only executed by master core and thus is candidate
for __init reaping.
So split it up to allow that.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
vs. fixed 512M before.
But this still assumes that all of memory is under IOC which may not be
true for the SoC. Improve that later when this becomes a real issue, by
specifying this from DT.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
On AXS103 release bitfiles, DMA data corruptions were seen because IOC
setup was not following the recommended way in documentation.
Flipping IOC on when caches are enabled or coherency transactions are in
flight, might cause some of the memory operations to not observe
coherency as expected.
So strictly follow the programming model recommendations as documented
in comment header above arc_ioc_setup()
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
commit d65283f7b6 added mod->arch.secstr under
CONFIG_ARC_DW2_UNWIND, but used it unconditionally which broke builds
when the option was disabled. Fix that by adjusting the #ifdef guard.
And while at it add a missing guard (for unwinder) in module.c as well
Reported-by: Waldemar Brodkorb <wbx@openadk.org>
Cc: stable@vger.kernel.org #4.9
Fixes: d65283f7b6 ("ARC: module: elide loop to save reference to .eh_frame")
Tested-by: Anton Kolesov <akolesov@synopsys.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
[abrodkin: provided fixlet to Kconfig per failure in allnoconfig build]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
It is necessary to call entry/exit functions for parent interrupt
controllers for proper masking/unmasking of interrupt lines.
Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
It is necessary to use hwirq instead of virq when you communicate
with an interrupt controller since there is no guaranty that virq
numbers match hwirq numbers.
Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
An ARC700 customer reported linux boot crashes when upgrading to bigger
L1 dcache (64K from 32K). Turns out they had an aliasing VIPT config and
current code only assumed 2 colours, while theirs had 4. So default to 4
colours and complain if there are fewer. Ideally this needs to be a
Kconfig option, but heck that's too much of hassle for a single user.
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Historical MMU revisions have been paired with Cache revision updates
which are captured in MMU and Cache Build Configuration Registers respectively.
This was used in boot code to check for configurations mismatches,
speically in simulations (such as running with non existent caches,
non pairing MMU and Cache version etc). This can instead be inferred
from other cache params such as line size. So remove @ver from post
processed @cpuinfo which could be used later to save soem other
interesting info.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
- Moving ARC timer driver into drivers/clocksource
- EZChip timer driver updates [Noam]
- ARC AXS103 and HAPS platform updates [Alexey]
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Merge tag 'arc-4.10-rc1-part1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc
Pull ARC updates from Vineet Gupta:
"These are mostly timer/clocksource driver updates which were
Reviewed/Acked by Daniel but had to be merged via ARC tree due to
dependencies.
I will follow up with another pull request with actual ARC changes
early next week !
Summary:
- Moving ARC timer driver into drivers/clocksource
- EZChip timer driver updates [Noam]
- ARC AXS103 and HAPS platform updates [Alexey]"
* tag 'arc-4.10-rc1-part1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
ARC: axs10x: really enable ARC PGU
ARC: rename Zebu platform support to HAPS
clocksource: nps: avoid maybe-uninitialized warning
clocksource: Add clockevent support to NPS400 driver
clocksource: update "fn" at CLOCKSOURCE_OF_DECLARE() of nps400 timer
soc: Support for NPS HW scheduling
clocksource: import ARC timer driver
ARC: breakout timer include code into separate header ...
ARC: move mcip.h into include/soc and adjust the includes
ARC: breakout aux handling into a separate header
ARC: time: move time_init() out of the driver
ARC: timer: gfrc, rtc: build under same option (64-bit timers)
ARC: timer: gfrc, rtc: Read BCR to detect whether hardware exists ...
ARC: timer: gfrc, rtc: deuglify big endian code
Fairly routine update this time around with all changes specific to drivers.
o New driver for STMicroelectronics FDMA
o Memory-to-memory transfers on dw dmac
o Support for slave maps on pl08x devices
o Bunch of driver fixes to use dma_pool_zalloc
o Bunch of compile and warning fixes spread across drivers
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Merge tag 'dmaengine-4.10-rc1' of git://git.infradead.org/users/vkoul/slave-dma
Pull dmaengine updates from Vinod Koul:
"Fairly routine update this time around with all changes specific to
drivers:
- New driver for STMicroelectronics FDMA
- Memory-to-memory transfers on dw dmac
- Support for slave maps on pl08x devices
- Bunch of driver fixes to use dma_pool_zalloc
- Bunch of compile and warning fixes spread across drivers"
[ The ST FDMA driver already came in earlier through the remoteproc tree ]
* tag 'dmaengine-4.10-rc1' of git://git.infradead.org/users/vkoul/slave-dma: (68 commits)
dmaengine: sirf-dma: remove unused ‘sdesc’
dmaengine: pl330: remove unused ‘regs’
dmaengine: s3c24xx: remove unused ‘cdata’
dmaengine: stm32-dma: remove unused ‘src_addr’
dmaengine: stm32-dma: remove unused ‘dst_addr’
dmaengine: stm32-dma: remove unused ‘sfcr’
dmaengine: pch_dma: remove unused ‘cookie’
dmaengine: mic_x100_dma: remove unused ‘data’
dmaengine: img-mdc: remove unused ‘prev_phys’
dmaengine: usb-dmac: remove unused ‘uchan’
dmaengine: ioat: remove unused ‘res’
dmaengine: ioat: remove unused ‘ioat_dma’
dmaengine: ioat: remove unused ‘is_raid_device’
dmaengine: pl330: do not generate unaligned access
dmaengine: k3dma: move to dma_pool_zalloc
dmaengine: at_hdmac: move to dma_pool_zalloc
dmaengine: at_xdmac: don't restore unsaved status
dmaengine: ioat: set error code on failures
dmaengine: ioat: set error code on failures
dmaengine: DW DMAC: add multi-block property to device tree
...
Patch series "Add support for DMA writable pages being writable by the
network stack", v3.
The first 19 patches in the set add support for the DMA attribute
DMA_ATTR_SKIP_CPU_SYNC on multiple platforms/architectures. This is
needed so that we can flag the calls to dma_map/unmap_page so that we do
not invalidate cache lines that do not currently belong to the device.
Instead we have to take care of this in the driver via a call to
sync_single_range_for_cpu prior to freeing the Rx page.
Patch 20 adds support for dma_map_page_attrs and dma_unmap_page_attrs so
that we can unmap and map a page using the DMA_ATTR_SKIP_CPU_SYNC
attribute.
Patch 21 adds support for freeing a page that has multiple references
being held by a single caller. This way we can free page fragments that
were allocated by a given driver.
The last 2 patches use these updates in the igb driver, and lay the
groundwork to allow for us to reimplement the use of build_skb.
This patch (of 23):
This change allows us to pass DMA_ATTR_SKIP_CPU_SYNC which allows us to
avoid invoking cache line invalidation if the driver will just handle it
later via a sync_for_cpu or sync_for_device call.
Link: http://lkml.kernel.org/r/20161110113419.76501.38491.stgit@ahduyck-blue-test.jf.intel.com
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ARC HS Cores support configurable multiple interrupt priorities of upto
16 levels. In commit dec2b2849c ("ARCv2: intc: Allow interruption by
lowest priority interrupt") we switched to 15 which seems a bit
excessive given that there would be rare hardware implementing so many
preemption levels AND running Linux. It would seem that 2 levels will be
more common so switch to 1 as the default priority level. This will be
the "lower" priority level saving 0 for implementing NMI style support.
This scheme also works in systems with more than 2 prioity levels as
well.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
And while at it - use the proper assembler macro which includes the
optional irq tracing already - de-uglify'ing the code a bit
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Up until now we had ARC PGU not enabled in axs10x defconfigs trying
to not bloat kernel image again with yet another drivers and subsystems.
This change configures ARC PGU (as well as DRM bits it depends on)
to be built as a module and so those who need LCD screen to work on
axs10x may bundle built .ko files in their target's file-system with
help of the following command on host:
------------->8-------------
make INSTALL_MOD_PATH=_path_to_target_fs_ modules_install
------------->8-------------
and later on target with commands as simple as:
------------->8-------------
modprobe adv7511.ko
modprobe arcpgu.ko
------------->8-------------
get LCD working.
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
There are more ARC Linux HAPS users than Zebu ones.
Same kernel would work fine on both, even with embedded DT, assuming the FPGA
bitfile configuration is same
Suggested-by: Francois Bedard <fbedard@ynopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This new header file is for NPS400 SoC (part of ARC architecture).
The header file includes macros for save/restore of HW scheduling.
The control of HW scheduling is achieved by writing core registers.
This code was moved from arc/plat-eznps so it can be used
from drivers/clocksource/, available only for CONFIG_EZNPS_MTM_EXT.
Signed-off-by: Noam Camus <noamca@mellanox.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
This adds support for
- CONFIG_ARC_TIMERS : legacy 32-bit TIMER0 and TIMER1 which count UP
from @CNT to @LIMIT, before optionally triggering an interrupt.
These are programmed using ARC auxiliary register interface.
These are present in all ARC cores (ARC700 and ARC HS38)
TIMER0 serves as clockevent for all ARC linux builds.
TIMER1 is used for clocksource in arc700 builds.
- CONFIG_ARC_TIMERS_64BIT: 64-bit counters, RTC and GFRC found in
ARC HS38 cores. These are independnet IP blocks with different
programming model respectively.
Link: http://lkml.kernel.org/r/20161111231132.GA4186@mai
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Also remove the dependency on ARCv2, to increase compile coverage for
!ARCV2 builds
Acked-by: Daniel Lezcano <daniel.lezcnao@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
ARC timers use aux registers for programming and this paves way for
moving ARC timer drivers into drivers/clocksource
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
to allow future git mv of the driver into drivers/clocksource
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
The original distinction was done as they were developed at different
times and primarily because they are specific to UP (RTC) and SMP (GFRC).
But given that driver handles that at runtime, (i.e. not allowing
RTC as clocksource in SMP), we can simplify things a bit.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
... don't rely on cpuinfo populated in arc boot code. This paves way for
moving this code in drivers/clocksource/
And while at it, convert the WARN() to pr_warn() as sugested by Daniel
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
A standard "C" shift will be handled appropriately by the compiler
depending on the endian for the build. So we don't need the
explicit distinction in code
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Several versions of DW DMAC have multi block transfers hardware
support. Hardware support of multi block transfers is disabled
by default if we use DT to configure DMAC and software emulation
of multi block transfers used instead.
Add multi-block property, so it is possible to enable hardware
multi block transfers (if present) via DT.
Switch from per device is_nollp variable to multi_block array
to be able enable/disable multi block transfers separately per
channel.
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
commit 1c3c909303 broke PAE40. Macro pfn_pte(pfn, prot) creates paddr
from pfn, but the page shift was getting truncated to 32 bits since we lost
the proper cast to 64 bits (for PAE400
Instead of reverting that commit, use a better helper which is 32/64 bits
safe just like ARM implementation.
Fixes: 1c3c909303 ("ARC: mm: fix build breakage with STRICT_MM_TYPECHECKS")
Cc: <stable@vger.kernel.org> #4.4+
Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
[vgupta: massaged changelog]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Apparenty this is coming in the way of gcc fix which inhibits the usage
of LP_COUNT as a gpr.
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
No need to duplicate the same define everywhere. Since
the only user is stop-machine and the only provider is
s390, we can use a default implementation of cpu_relax_yield()
in sched.h.
Suggested-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kvm@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: linux-s390 <linux-s390@vger.kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: sparclinux@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1479298985-191589-1-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As there are no users left, we can remove cpu_relax_lowlatency()
implementations from every architecture.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Cc: <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1477386195-32736-6-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
For spinning loops people do often use barrier() or cpu_relax().
For most architectures cpu_relax and barrier are the same, but on
some architectures cpu_relax can add some latency.
For example on power,sparc64 and arc, cpu_relax can shift the CPU
towards other hardware threads in an SMT environment.
On s390 cpu_relax does even more, it uses an hypercall to the
hypervisor to give up the timeslice.
In contrast to the SMT yielding this can result in larger latencies.
In some places this latency is unwanted, so another variant
"cpu_relax_lowlatency" was introduced. Before this is used in more
and more places, lets revert the logic and provide a cpu_relax_yield
that can be called in places where yielding is more important than
latency. By default this is the same as cpu_relax on all architectures.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: virtualization@lists.linux-foundation.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1477386195-32736-2-git-send-email-borntraeger@de.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
- mmap handler for dma ops as generic handler no longer works for us [Alexey]
- Fixes for EZChip platform [Noam]
- Fix RTC clocksource driver build issue
- ARC IRQ handling fixes [Yuriy]
- Revert a recent makefile change which doesn't go well with oldish tools out in the wild
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Merge tag 'arc-4.9-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc
Pull ARC fixes from Vineet Gupta:
- mmap handler for dma ops as generic handler no longer works for us
[Alexey]
- Fixes for EZChip platform [Noam]
- Fix RTC clocksource driver build issue
- ARC IRQ handling fixes [Yuriy]
- Revert a recent makefile change which doesn't go well with oldish
tools out in the wild
* tag 'arc-4.9-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
ARCv2: MCIP: Use IDU_M_DISTRI_DEST mode if there is only 1 destination core
ARC: IRQ: Do not use hwirq as virq and vice versa
ARC: [plat-eznps] set default baud for early console
ARC: [plat-eznps] remove IPI clear from SMP operations
Revert "ARC: build: retire old toggles"
ARC: timer: rtc: implement read loop in "C" vs. inline asm
ARC: change return value of userspace cmpxchg assist syscall
arc: Implement arch-specific dma_map_ops.mmap
ARC: [SMP] avoid overriding present cpumask
ARC: Enable PERF_EVENTS in nSIM driven platforms
Traditionally, we have always had warnings about uninitialized variables
enabled, as this is part of -Wall, and generally a good idea [1], but it
also always produced false positives, mainly because this is a variation
of the halting problem and provably impossible to get right in all cases
[2].
Various people have identified cases that are particularly bad for false
positives, and in commit e74fc973b6 ("Turn off -Wmaybe-uninitialized
when building with -Os"), I turned off the warning for any build that
was done with CC_OPTIMIZE_FOR_SIZE. This drastically reduced the number
of false positive warnings in the default build but unfortunately had
the side effect of turning the warning off completely in 'allmodconfig'
builds, which in turn led to a lot of warnings (both actual bugs, and
remaining false positives) to go in unnoticed.
With commit 877417e6ff ("Kbuild: change CC_OPTIMIZE_FOR_SIZE
definition") enabled the warning again for allmodconfig builds in v4.7
and in v4.8-rc1, I had finally managed to address all warnings I get in
an ARM allmodconfig build and most other maybe-uninitialized warnings
for ARM randconfig builds.
However, commit 6e8d666e92 ("Disable "maybe-uninitialized" warning
globally") was merged at the same time and disabled it completely for
all configurations, because of false-positive warnings on x86 that I had
not addressed until then. This caused a lot of actual bugs to get
merged into mainline, and I sent several dozen patches for these during
the v4.9 development cycle. Most of these are actual bugs, some are for
correct code that is safe because it is only called under external
constraints that make it impossible to run into the case that gcc sees,
and in a few cases gcc is just stupid and finds something that can
obviously never happen.
I have now done a few thousand randconfig builds on x86 and collected
all patches that I needed to address every single warning I got (I can
provide the combined patch for the other warnings if anyone is
interested), so I hope we can get the warning back and let people catch
the actual bugs earlier.
This reverts the change to disable the warning completely and for now
brings it back at the "make W=1" level, so we can get it merged into
mainline without introducing false positives. A follow-up patch enables
it on all levels unless some configuration option turns it off because
of false-positives.
Link: https://rusty.ozlabs.org/?p=232 [1]
Link: https://gcc.gnu.org/wiki/Better_Uninitialized_Warnings [2]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
