This can be used to create a separate DRM file description, thus
creating a new GEM handle namespace.
My use-case is wlroots. The library splits responsibilities between
separate components: the GBM allocator creates buffers, the GLES2
renderer uses EGL to import them and render to them, the DRM
backend imports the buffers and displays them. wlroots has a
modular architecture, and any of these components can be swapped
and replaced with something else. For instance, the pipeline can
be set up so that the DRM dumb buffer allocator is used instead of
GBM and the Pixman renderer is used instead of GLES2. Library users
can also replace any of these components with their own custom one.
DMA-BUFs are used to pass buffer references across components. We
could use GEM handles instead, but this would result in pain if
multiple GPUs are in use: wlroots copies buffers across GPUs as
needed. Importing a GEM handle created on one GPU into a completely
different GPU will blow up (fail at best, mix unrelated buffers
otherwise).
Everything is fine if all components use Mesa. However, this isn't
always desirable. For instance when running with DRM dumb buffers
and the Pixman software renderer it's unfortunate to depend on GBM
in the DRM backend just to turn DMA-BUFs into FB IDs. GBM loads
Mesa drivers to perform an action which has nothing driver-specific.
Additionally, drivers will fail the import if the 3D engine can't
use the imported buffer, for instance amdgpu will refuse to import
DRM dumb buffers [1]. We might also want to be running with a Vulkan
renderer and a Vulkan allocator in the future, and GBM wouldn't be
welcome in this setup.
To address this, GBM can be side-stepped in the DRM backend, and
can be replaced with drmPrimeFDToHandle calls. However because of
GEM handle reference counting issues, care must be taken to avoid
double-closing the same GEM handle. In particular, it's not
possible to share a DRM FD with GBM or EGL and perform some
drmPrimeFDToHandle calls manually.
So wlroots needs to re-open the DRM FD to create a new GEM handle
namespace. However there's no guarantee that the file-system
permissions will be set up so that the primary FD can be opened
by the compsoitor. On modern systems seatd or logind is a privileged
process responsible for doing this, and other processes aren't
expected to do it. For historical reasons systemd still allows
physically logged in users to open primary DRM nodes, but this
doesn't work on non-systemd setups and it's desirable to lock
them down at some point.
Some might suggest to open the render node instead of re-opening
the primary node. However some systems don't have a render node
at all (e.g. no GPU, or a split render/display SoC).
Solutions to this issue have been discussed in [2]. One solution
would be to open the magic /proc/self/fd/<fd> file, but it's a
Linux-specific hack (wlroots supports BSDs too). Another solution
is to add support for re-opening a DRM primary node to seatd/logind,
but they don't support it now and really haven't been designed for
this (logind would need to grow a completely new API, because it
assumes unique dev_t IDs). Also this seems like pushing down a
kernel limitation to user-space a bit too hard.
Another solution is to allow creating empty DRM leases. The lessee
FD would have its own GEM handle namespace, so wouldn't conflict
wth GBM/EGL. It would have the master bit set, but would be able
to manage zero resources. wlroots doesn't intend to share this FD
with any other process.
All in all IMHO that seems like a pretty reasonable solution to the
issue at hand.
Note, I've discussed with Jonas Ådahl and Mutter plans to adopt a
similar design in the future.
Example usage in wlroots is available at [3]. IGT test available
at [4].
[1]: https://github.com/swaywm/wlroots/issues/2916
[2]: https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110
[3]: https://github.com/swaywm/wlroots/pull/3158
[4]: https://patchwork.freedesktop.org/series/94323/
Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Daniel Stone <daniels@collabora.com>
Cc: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Cc: Michel Dänzer <michel@daenzer.net>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Keith Packard <keithp@keithp.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Dave Airlie <airlied@redhat.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210903130000.1590-2-contact@emersion.fr
CONFIG_SPARSEMEM_VMEMMAP is now the only available memory model on arm64
platforms and free_unused_memmap() would just return without creating any
holes in the memmap mapping. There is no need for any special handling in
pfn_valid() and HAVE_ARCH_PFN_VALID can just be dropped. This also moves
the pfn upper bits sanity check into generic pfn_valid().
[rppt: rebased on v5.15-rc3]
Link: https://lkml.kernel.org/r/1621947349-25421-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/20210930013039.11260-3-rppt@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.
As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().
Link: https://lore.kernel.org/all/20210824173741.GC623@arm.com/
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20210930013039.11260-2-rppt@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Each region has an independently configurable number of maximum
snapshots. This information is not reported to userspace, making it not
very discoverable. Fix this by adding a new
DEVLINK_ATTR_REGION_MAX_SNAPSHOST attribute which is used to report this
maximum.
Ex:
$devlink region
pci/0000:af:00.0/nvm-flash: size 10485760 snapshot [] max 1
pci/0000:af:00.0/device-caps: size 4096 snapshot [] max 10
pci/0000:af:00.1/nvm-flash: size 10485760 snapshot [] max 1
pci/0000:af:00.1/device-caps: size 4096 snapshot [] max 10
This information enables users to understand why a new region command
may fail due to having too many existing snapshots.
Reported-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Jeremy Kerr says:
====================
MCTP kunit tests
This change adds some initial kunit tests for the MCTP core. We'll
expand the coverage in a future series, and augment with a few
selftests, but this establishes a baseline set of tests for now.
Thanks to the kunit folks for the framework!
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Add multi-packet route input tests, for message reassembly. These will
feed packets to be received by a bound socket, or dropped.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a few tests for single-packet route inputs, testing the
mctp_route_input function.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a few tests for the initial packet ingress through
mctp_pkttype_receive function; mainly packet header sanity checks. Full
input routing checks will be added as a separate change.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This change adds the first kunit test for the mctp subsystem, and an
initial test for the fragmentation path.
We're adding tests under a new net/mctp/test/ directory.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Second set of fixes for v5.15, nothing major this time. Most important
here are reverting a brcmfmac regression and a fix for an old rare
ath5k build error.
iwlwifi
* fixes to NULL dereference, off by one and missing unlock
* add support for Killer AX1650 on Dell XPS 15 (9510) laptop
ath5k
* build fix with LEDS=m
brcmfmac
* revert a regression causing BCM4359/9 devices stop working as access point
mwifiex
* fix clang warning about null pointer arithmetic
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Merge tag 'wireless-drivers-2021-10-01' of git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers
wireless-drivers fixes for v5.15
Second set of fixes for v5.15, nothing major this time. Most important
here are reverting a brcmfmac regression and a fix for an old rare
ath5k build error.
iwlwifi
* fixes to NULL dereference, off by one and missing unlock
* add support for Killer AX1650 on Dell XPS 15 (9510) laptop
ath5k
* build fix with LEDS=m
brcmfmac
* revert a regression causing BCM4359/9 devices stop working as access point
mwifiex
* fix clang warning about null pointer arithmetic
"CRTC fixup failed" is probably leftovers from pre-atomic days
when there was an actual fixup() function. Let's unify the debug
messages between encoder vs. crtc compute_config() calls.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210930104133.30854-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
The intend of trans_pgd_map_page() was to map contiguous range of VA
memory to the memory that is getting relocated during kexec. However,
since we are now using linear map instead of contiguous range this
function is not needed
Suggested-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-16-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
This header contains only cpu_soft_restart() which is never used directly
anymore. So, remove this header, and rename the helper to be
cpu_soft_restart().
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-15-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Now that kexec does its relocations with the MMU enabled, we no longer
need to clean the relocation data to the PoC.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-14-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Now, that we have linear map page tables configured, keep MMU enabled
to allow faster relocation of segments to final destination.
Cavium ThunderX2:
Kernel Image size: 38M Iniramfs size: 46M Total relocation size: 84M
MMU-disabled:
relocation 7.489539915s
MMU-enabled:
relocation 0.03946095s
Broadcom Stingray:
The performance data: for a moderate size kernel + initramfs: 25M the
relocation was taking 0.382s, with enabled MMU it now takes
0.019s only or x20 improvement.
The time is proportional to the size of relocation, therefore if initramfs
is larger, 100M it could take over a second.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Tested-by: Pingfan Liu <piliu@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-13-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
To perform the kexec relocation with the MMU enabled, we need a copy
of the linear map.
Create one, and install it from the relocation code. This has to be done
from the assembly code as it will be idmapped with TTBR0. The kernel
runs in TTRB1, so can't use the break-before-make sequence on the mapping
it is executing from.
The makes no difference yet as the relocation code runs with the MMU
disabled.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-12-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently, relocation code declares start and end variables
which are used to compute its size.
The better way to do this is to use ld script, and put relocation
function in its own section.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-11-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Since we are going to keep MMU enabled during relocation, we need to
keep EL1 mode throughout the relocation.
Keep EL1 enabled, and switch EL2 only before entering the new world.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-10-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
If we have a EL2 mode without VHE, the EL2 vectors are needed in order
to switch to EL2 and jump to new world with hypervisor privileges.
In preparation to MMU enabled relocation, configure our EL2 table now.
Kexec uses #HVC_SOFT_RESTART to branch to the new world, so extend
el1_sync vector that is provided by trans_pgd_copy_el2_vectors() to
support this case.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-9-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently, kexec relocation function (arm64_relocate_new_kernel) accepts
the following arguments:
head: start of array that contains relocation information.
entry: entry point for new kernel or purgatory.
dtb_mem: first and only argument to entry.
The number of arguments cannot be easily expended, because this
function is also called from HVC_SOFT_RESTART, which preserves only
three arguments. And, also arm64_relocate_new_kernel is written in
assembly but called without stack, thus no place to move extra arguments
to free registers.
Soon, we will need to pass more arguments: once we enable MMU we
will need to pass information about page tables.
Pass kimage to arm64_relocate_new_kernel, and teach it to get the
required fields from kimage.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-8-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
kexec does dcache maintenance when it re-writes all memory. Our
dcache_by_line_op macro depends on reading the sanitized DminLine
from memory. Kexec may have overwritten this, so open-codes the
sequence.
dcache_by_line_op is a whole set of macros, it uses dcache_line_size
which uses read_ctr for the sanitsed DminLine. Reading the DminLine
is the first thing the dcache_by_line_op does.
Rename dcache_by_line_op dcache_by_myline_op and take DminLine as
an argument. Kexec can now use the slightly smaller macro.
This makes up-coming changes to the dcache maintenance easier on
the eye.
Code generated by the existing callers is unchanged.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-7-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
In case of kdump or when segments are already in place the relocation
is not needed, therefore the setup of relocation function and call to
it can be skipped.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Suggested-by: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-6-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently, during kexec load we are copying relocation function and
flushing it. However, we can also flush kexec relocation buffers and
if new kernel image is already in place (i.e. crash kernel), we can
also flush the new kernel image itself.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-5-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Currently, only hibernate sets custom ttbr0 with safe idmaped function.
Kexec, is also going to be using this functionality when relocation code
is going to be idmapped.
Move the setup sequence to a dedicated cpu_install_ttbr0() for custom
ttbr0.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-4-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Users of trans_pgd may also need a copy of vector table because it is
also may be overwritten if a linear map can be overwritten.
Move setup of EL2 vectors from hibernate to trans_pgd, so it can be
later shared with kexec as well.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-3-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
Replace places that contain logic like this:
is_hyp_mode_available() && !is_kernel_in_hyp_mode()
With a dedicated boolean function is_hyp_nvhe(). This will be needed
later in kexec in order to sooner switch back to EL2.
Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210930143113.1502553-2-pasha.tatashin@soleen.com
Signed-off-by: Will Deacon <will@kernel.org>
percpu_ref_tryget_live() is safe to call as long as ref is between init and
exit according to the function comment. Move percpu_ref_exit() so it is
called after the dma channel is no longer valid to ensure this holds true.
Fixes: 93a40a6d74 ("dmaengine: idxd: add percpu_ref to descriptor submission path")
Suggested-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163294293832.914350.10326422026738506152.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Since commit a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to
list on unthrottle") we add cfs_rqs with no runnable tasks but not fully
decayed into the load (leaf) list. We may ignore adding some ancestors
and therefore breaking tmp_alone_branch invariant. This broke LTP test
cfs_bandwidth01 and it was partially fixed in commit fdaba61ef8
("sched/fair: Ensure that the CFS parent is added after unthrottling").
I noticed the named test still fails even with the fix (but with low
probability, 1 in ~1000 executions of the test). The reason is when
bailing out of unthrottle_cfs_rq early, we may miss adding ancestors of
the unthrottled cfs_rq, thus, not joining tmp_alone_branch properly.
Fix this by adding ancestors if we notice the unthrottled cfs_rq was
added to the load list.
Fixes: a7b359fc6a ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Odin Ugedal <odin@uged.al>
Link: https://lore.kernel.org/r/20210917153037.11176-1-mkoutny@suse.com
Users of rdpmc rely on the mmapped user page to calculate accurate
time_enabled. Currently, userpage->time_enabled is only updated when the
event is added to the pmu. As a result, inactive event (due to counter
multiplexing) does not have accurate userpage->time_enabled. This can
be reproduced with something like:
/* open 20 task perf_event "cycles", to create multiplexing */
fd = perf_event_open(); /* open task perf_event "cycles" */
userpage = mmap(fd); /* use mmap and rdmpc */
while (true) {
time_enabled_mmap = xxx; /* use logic in perf_event_mmap_page */
time_enabled_read = read(fd).time_enabled;
if (time_enabled_mmap > time_enabled_read)
BUG();
}
Fix this by updating userpage for inactive events in merge_sched_in.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-and-tested-by: Lucian Grijincu <lucian@fb.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210929194313.2398474-1-songliubraving@fb.com
According to the latest event list, the event encoding 0xEF is only
available on the first 4 counters. Add it into the event constraints
table.
Fixes: 6017608936 ("perf/x86/intel: Add Icelake support")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1632842343-25862-1-git-send-email-kan.liang@linux.intel.com
perf_init_event tries multiple init callbacks and does not reset the
event state between tries. When x86_pmu_event_init runs, it
unconditionally sets the destroy callback to hw_perf_event_destroy. On
the next init attempt after x86_pmu_event_init, in perf_try_init_event,
if the pmu's capabilities includes PERF_PMU_CAP_NO_EXCLUDE, the destroy
callback will be run. However, if the next init didn't set the destroy
callback, hw_perf_event_destroy will be run (since the callback wasn't
reset).
Looking at other pmu init functions, the common pattern is to only set
the destroy callback on a successful init. Resetting the callback on
failure tries to replicate that pattern.
This was discovered after commit f11dd0d805 ("perf/x86/amd/ibs: Extend
PERF_PMU_CAP_NO_EXCLUDE to IBS Op") when the second (and only second)
run of the perf tool after a reboot results in 0 samples being
generated. The extra run of hw_perf_event_destroy results in
active_events having an extra decrement on each perf run. The second run
has active_events == 0 and every subsequent run has active_events < 0.
When active_events == 0, the NMI handler will early-out and not record
any samples.
Signed-off-by: Anand K Mistry <amistry@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210929170405.1.I078b98ee7727f9ae9d6df8262bad7e325e40faf0@changeid
The rw_semaphore and rwlock_t implementation both wake the waiter while
holding the rt_mutex_base::wait_lock acquired.
This can be optimized by waking the waiter lockless outside of the
locked section to avoid a needless contention on the
rt_mutex_base::wait_lock lock.
Extend rt_mutex_wake_q_add() to also accept task and state and use it in
__rwbase_read_unlock().
Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928150006.597310-3-bigeasy@linutronix.de
rt_mutex_wake_q_add() needs to need to distiguish between sleeping
locks (TASK_RTLOCK_WAIT) and normal locks which use TASK_NORMAL to use
the proper wake mechanism.
Instead of checking for != TASK_NORMAL make it more robust and check
explicit for TASK_RTLOCK_WAIT which is the reason why a different wake
mechanism is used.
No functional change.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210928150006.597310-2-bigeasy@linutronix.de
The general rule that rcu_read_lock() held sections cannot voluntary sleep
does apply even on RT kernels. Though the substitution of spin/rw locks on
RT enabled kernels has to be exempt from that rule. On !RT a spin_lock()
can obviously nest inside a RCU read side critical section as the lock
acquisition is not going to block, but on RT this is not longer the case
due to the 'sleeping' spinlock substitution.
The RT patches contained a cheap hack to ignore the RCU nesting depth in
might_sleep() checks, which was a pragmatic but incorrect workaround.
Instead of generally ignoring the RCU nesting depth in __might_sleep() and
__might_resched() checks, pass the rcu_preempt_depth() via the offsets
argument to __might_resched() from spin/read/write_lock() which makes the
checks work correctly even in RCU read side critical sections.
The actual blocking on such a substituted lock within a RCU read side
critical section is already handled correctly in __schedule() by treating
it as a "preemption" of the RCU read side critical section.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.368305497@linutronix.de
The __might_resched() checks in the cond_resched_lock() variants use
PREEMPT_LOCK_OFFSET for preempt count offset checking which takes the
preemption disable by the spin_lock() which is still held at that point
into account.
On PREEMPT_RT enabled kernels spin/rw_lock held sections stay preemptible
which means PREEMPT_LOCK_OFFSET is 0, but that still triggers the
__might_resched() check because that takes RCU read side nesting into
account.
On RT enabled kernels spin/read/write_lock() issue rcu_read_lock() to
resemble the !RT semantics, which means in cond_resched_lock() the might
resched check will see preempt_count() == 0 and rcu_preempt_depth() == 1.
Introduce PREEMPT_LOCK_SCHED_OFFSET for those might resched checks and map
them depending on CONFIG_PREEMPT_RT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.305969211@linutronix.de
For !RT kernels RCU nest depth in __might_resched() is always expected to
be 0, but on RT kernels it can be non zero while the preempt count is
expected to be always 0.
Instead of playing magic games in interpreting the 'preempt_offset'
argument, rename it to 'offsets' and use the lower 8 bits for the expected
preempt count, allow to hand in the expected RCU nest depth in the upper
bits and adopt the __might_resched() code and related checks and printks.
The affected call sites are updated in subsequent steps.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.243232823@linutronix.de
might_sleep() output is pretty informative, but can be confusing at times
especially with PREEMPT_RCU when the check triggers due to a voluntary
sleep inside a RCU read side critical section:
BUG: sleeping function called from invalid context at kernel/test.c:110
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
Preemption disabled at: migrate_disable+0x33/0xa0
in_atomic() is 0, but it still tells that preemption was disabled at
migrate_disable(), which is completely useless because preemption is not
disabled. But the interesting information to decode the above, i.e. the RCU
nesting depth, is not printed.
That becomes even more confusing when might_sleep() is invoked from
cond_resched_lock() within a RCU read side critical section. Here the
expected preemption count is 1 and not 0.
BUG: sleeping function called from invalid context at kernel/test.c:131
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
Preemption disabled at: test_cond_lock+0xf3/0x1c0
So in_atomic() is set, which is expected as the caller holds a spinlock,
but it's unclear why this is broken and the preempt disable IP is just
pointing at the correct place, i.e. spin_lock(), which is obviously not
helpful either.
Make that more useful in general:
- Print preempt_count() and the expected value
and for the CONFIG_PREEMPT_RCU case:
- Print the RCU read side critical section nesting depth
- Print the preempt disable IP only when preempt count
does not have the expected value.
So the might_sleep() dump from a within a preemptible RCU read side
critical section becomes:
BUG: sleeping function called from invalid context at kernel/test.c:110
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
and the cond_resched_lock() case becomes:
BUG: sleeping function called from invalid context at kernel/test.c:141
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 415, name: kworker/u112:52
preempt_count: 1, expected: 1
RCU nest depth: 1, expected: 0
which makes is pretty obvious what's going on. For all other cases the
preempt disable IP is still printed as before:
BUG: sleeping function called from invalid context at kernel/test.c: 156
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
Preemption disabled at:
[<ffffffff82b48326>] test_might_sleep+0xbe/0xf8
BUG: sleeping function called from invalid context at kernel/test.c: 163
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 0
Preemption disabled at:
[<ffffffff82b48326>] test_might_sleep+0x1e4/0x280
This also prepares to provide a better debugging output for RT enabled
kernels and their spinlock substitutions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165358.181022656@linutronix.de
Commit 3427445afd ("sched: Exclude cond_resched() from nested sleep
test") removed the task state check of __might_sleep() for
cond_resched_lock() because cond_resched_lock() is not a voluntary
scheduling point which blocks. It's a preemption point which requires the
lock holder to release the spin lock.
The same rationale applies to cond_resched_rwlock_read/write(), but those
were not touched.
Make it consistent and use the non-state checking __might_resched() there
as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165357.991262778@linutronix.de
__might_sleep() vs. ___might_sleep() is hard to distinguish. Aside of that
the three underscore variant is exposed to provide a checkpoint for
rescheduling points which are distinct from blocking points.
They are semantically a preemption point which means that scheduling is
state preserving. A real blocking operation, e.g. mutex_lock(), wait*(),
which cannot preserve a task state which is not equal to RUNNING.
While technically blocking on a "sleeping" spinlock in RT enabled kernels
falls into the voluntary scheduling category because it has to wait until
the contended spin/rw lock becomes available, the RT lock substitution code
can semantically be mapped to a voluntary preemption because the RT lock
substitution code and the scheduler are providing mechanisms to preserve
the task state and to take regular non-lock related wakeups into account.
Rename ___might_sleep() to __might_resched() to make the distinction of
these functions clear.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210923165357.928693482@linutronix.de
Clang warns:
kernel/locking/test-ww_mutex.c:138:7: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
if (!ww_mutex_trylock(&mutex, &ctx)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:172:9: note: uninitialized use occurs here
return ret;
^~~
kernel/locking/test-ww_mutex.c:138:3: note: remove the 'if' if its condition is always false
if (!ww_mutex_trylock(&mutex, &ctx)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:125:9: note: initialize the variable 'ret' to silence this warning
int ret;
^
= 0
1 error generated.
Assign !ww_mutex_trylock(...) to ret so that it is always initialized.
Fixes: 12235da8c8 ("kernel/locking: Add context to ww_mutex_trylock()")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20210922145822.3935141-1-nathan@kernel.org
Occasionally objtool encounters symbol (as opposed to section)
relocations in .altinstructions. Typically they are the alternatives
written by elf_add_alternative() as encountered on a noinstr
validation run on vmlinux after having already ran objtool on the
individual .o files.
Basically this is the counterpart of commit 44f6a7c075 ("objtool:
Fix seg fault with Clang non-section symbols"), because when these new
assemblers (binutils now also does this) strip the section symbols,
elf_add_reloc_to_insn() is forced to emit symbol based relocations.
As such, teach get_alt_entry() about different relocation types.
Fixes: 9bc0bb5072 ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net
