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This commit retrospectively prepares for testing of RCU readers invoked
from hardware interrupt handlers (for example, HRTIMER_MODE_HARD hrtimer
handlers) in kernels built with CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE=y,
which is rarely used but sometimes extremely useful. This preparation
involves taking early exits if in_hardirq(), and, while we are in the
area, a very early exit if in_nmi().
This means that a number of insoftirq parameters are no longer needed,
but that is the subject of a later commit.
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202505140917.8ee62cc6-lkp@intel.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
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Testing of rcutorture's SRCU-P scenario on a large arm64 system resulted
in rcu_torture_writer() forward-progress failures, but these same tests
passed on x86. After some off-list discussion of possible memory-ordering
causes for these failures, Boqun showed that these were in fact due to
reordering, but by the scheduler, not by the memory system. On x86,
rcu_torture_writer() would have run quickly enough that by the time
the rcu_torture_updown() kthread started, the rcu_torture_current
variable would already be initialized, thus avoiding a bug in which
a NULL value would cause rcu_torture_updown() to do an extra call to
srcu_up_read_fast().
This commit therefore moves creation of the rcu_torture_writer() kthread
after that of the rcu_torture_reader() kthreads. This results in
deterministic failures on x86.
What about the double-srcu_up_read_fast() bug? Boqun has the fix.
But let's also fix the test while we are at it!
Reported-by: Joel Fernandes <joelagnelf@nvidia.com>
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
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The rcu_torture_writer() function scans the memory blocks after a stutter
(or forced idle) interval, complaining about any that have not passed
through ten grace periods since the start of the stutter interval.
But one splat suffices, so this commit therefore stops at the first splat.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
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RCU relies on the context tracking nesting counter in order to determine
if it is running in extended quiescent state.
However the context tracking nesting counter is not completely
synchronized with the actual context tracking state:
* The nesting counter is set to 1 or incremented further _after_ the
actual state is set to RCU watching.
* The nesting counter is set to 0 or decremented further _before_ the
actual state is set to RCU not watching.
Therefore it is safe to assume that if ct_nesting() > 0, RCU is
watching. But if ct_nesting() <= 0, RCU is not watching except for tiny
windows.
This hasn't been a problem so far because rcu_is_cpu_rrupt_from_idle()
has only been called from interrupts. However the code is confusing
and abuses the role of the context tracking nesting counter while there
are more accurate indicators available.
Clarify and robustify accordingly.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
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When a grace period is started, the ->expmask of each node is set up
from sync_exp_reset_tree(). Then later on each leaf node also initialize
its ->exp_tasks pointer.
This means that the initialization of the quiescent state of a node and
the initialization of its blocking tasks happen with an unlocked node
gap in-between.
It happens to be fine because nothing is expected to report an exp
quiescent state within this gap, since no IPI have been issued yet and
every rdp's ->cpu_no_qs.b.exp should be false.
However if it were to happen by accident, the quiescent state could be
reported and propagated while ignoring tasks that blocked _before_ the
start of the grace period.
Prevent such trouble to happen in the future and initialize both the
quiescent states mask to report and the blocked tasks head from the same
node locked block.
If a task blocks within an RCU read side critical section before
sync_exp_reset_tree() is called and is then unblocked between
sync_exp_reset_tree() and __sync_rcu_exp_select_node_cpus(), the QS
won't be reported because no RCU exp IPI had been issued to request it
through the setting of srdp->cpu_no_qs.b.exp.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>
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This patch improves the precison of the scalar(32)_min_max_add and
scalar(32)_min_max_sub functions, which update the u(32)min/u(32)_max
ranges for the BPF_ADD and BPF_SUB instructions. We discovered this more
precise operator using a technique we are developing for automatically
synthesizing functions for updating tnums and ranges.
According to the BPF ISA [1], "Underflow and overflow are allowed during
arithmetic operations, meaning the 64-bit or 32-bit value will wrap".
Our patch leverages the wrap-around semantics of unsigned overflow and
underflow to improve precision.
Below is an example of our patch for scalar_min_max_add; the idea is
analogous for all four functions.
There are three cases to consider when adding two u64 ranges [dst_umin,
dst_umax] and [src_umin, src_umax]. Consider a value x in the range
[dst_umin, dst_umax] and another value y in the range [src_umin,
src_umax].
(a) No overflow: No addition x + y overflows. This occurs when even the
largest possible sum, i.e., dst_umax + src_umax <= U64_MAX.
(b) Partial overflow: Some additions x + y overflow. This occurs when
the largest possible sum overflows (dst_umax + src_umax > U64_MAX), but
the smallest possible sum does not overflow (dst_umin + src_umin <=
U64_MAX).
(c) Full overflow: All additions x + y overflow. This occurs when both
the smallest possible sum and the largest possible sum overflow, i.e.,
both (dst_umin + src_umin) and (dst_umax + src_umax) are > U64_MAX.
The current implementation conservatively sets the output bounds to
unbounded, i.e, [umin=0, umax=U64_MAX], whenever there is *any*
possibility of overflow, i.e, in cases (b) and (c). Otherwise it
computes tight bounds as [dst_umin + src_umin, dst_umax + src_umax]:
if (check_add_overflow(*dst_umin, src_reg->umin_value, dst_umin) ||
check_add_overflow(*dst_umax, src_reg->umax_value, dst_umax)) {
*dst_umin = 0;
*dst_umax = U64_MAX;
}
Our synthesis-based technique discovered a more precise operator.
Particularly, in case (c), all possible additions x + y overflow and
wrap around according to eBPF semantics, and the computation of the
output range as [dst_umin + src_umin, dst_umax + src_umax] continues to
work. Only in case (b), do we need to set the output bounds to
unbounded, i.e., [0, U64_MAX].
Case (b) can be checked by seeing if the minimum possible sum does *not*
overflow and the maximum possible sum *does* overflow, and when that
happens, we set the output to unbounded:
min_overflow = check_add_overflow(*dst_umin, src_reg->umin_value, dst_umin);
max_overflow = check_add_overflow(*dst_umax, src_reg->umax_value, dst_umax);
if (!min_overflow && max_overflow) {
*dst_umin = 0;
*dst_umax = U64_MAX;
}
Below is an example eBPF program and the corresponding log from the
verifier.
The current implementation of scalar_min_max_add() sets r3's bounds to
[0, U64_MAX] at instruction 5: (0f) r3 += r3, due to conservative
overflow handling.
0: R1=ctx() R10=fp0
0: (b7) r4 = 0 ; R4_w=0
1: (87) r4 = -r4 ; R4_w=scalar()
2: (18) r3 = 0xa000000000000000 ; R3_w=0xa000000000000000
4: (4f) r3 |= r4 ; R3_w=scalar(smin=0xa000000000000000,smax=-1,umin=0xa000000000000000,var_off=(0xa000000000000000; 0x5fffffffffffffff)) R4_w=scalar()
5: (0f) r3 += r3 ; R3_w=scalar()
6: (b7) r0 = 1 ; R0_w=1
7: (95) exit
With our patch, r3's bounds after instruction 5 are set to a much more
precise [0x4000000000000000,0xfffffffffffffffe].
...
5: (0f) r3 += r3 ; R3_w=scalar(umin=0x4000000000000000,umax=0xfffffffffffffffe)
6: (b7) r0 = 1 ; R0_w=1
7: (95) exit
The logic for scalar32_min_max_add is analogous. For the
scalar(32)_min_max_sub functions, the reasoning is similar but applied
to detecting underflow instead of overflow.
We verified the correctness of the new implementations using Agni [3,4].
We since also discovered that a similar technique has been used to
calculate output ranges for unsigned interval addition and subtraction
in Hacker's Delight [2].
[1] https://docs.kernel.org/bpf/standardization/instruction-set.html
[2] Hacker's Delight Ch.4-2, Propagating Bounds through Add’s and Subtract’s
[3] https://github.com/bpfverif/agni
[4] https://people.cs.rutgers.edu/~sn349/papers/sas24-preprint.pdf
Co-developed-by: Matan Shachnai <m.shachnai@rutgers.edu>
Signed-off-by: Matan Shachnai <m.shachnai@rutgers.edu>
Co-developed-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Signed-off-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Co-developed-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250623040359.343235-2-harishankar.vishwanathan@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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For systems using a sched_ext scheduler and has panic_on_rcu_stall
enabled, try kicking out the current scheduler before issuing a panic.
While there are numerous reasons for RCU CPU stalls that are not
directly attributed to the scheduler, deferring the panic gives
sched_ext an opportunity to provide additional debug info when ejecting
the current scheduler. Also, handling the event more gracefully allows
us to potentially recover the system instead of incurring additional
down time.
Suggested-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: David Dai <david.dai@linux.dev>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Fix the following:
In kernel/gen_kheaders.sh line 48:
-I $XZ -cf $tarfile -C "${tmpdir}/" . > /dev/null
^-^ SC2086 (info): Double quote to prevent globbing and word splitting.
^------^ SC2086 (info): Double quote to prevent globbing and word splitting.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This problem is similar to commit 7f8256ae0efb ("initramfs: Encode
dependency on KBUILD_BUILD_TIMESTAMP"): kernel/gen_kheaders.sh has an
internal dependency on KBUILD_BUILD_TIMESTAMP that is not exposed to
make, so changing KBUILD_BUILD_TIMESTAMP will not trigger a rebuild
of the archive.
Move $(KBUILD_BUILD_TIMESTAMP) to the Makefile so that is is recorded
in the *.cmd file.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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When a header file is changed, kernel/gen_kheaders.sh may fail to update
kernel/kheaders_data.tar.xz.
[steps to reproduce]
[1] Build kernel/kheaders_data.tar.xz
$ make -j$(nproc) kernel/kheaders.o
DESCEND objtool
INSTALL libsubcmd_headers
CALL scripts/checksyscalls.sh
CHK kernel/kheaders_data.tar.xz
GEN kernel/kheaders_data.tar.xz
CC kernel/kheaders.o
[2] Modify a header without changing the file size
$ sed -i s/0xdeadbeef/0xfeedbeef/ include/linux/elfnote.h
[3] Rebuild kernel/kheaders_data.tar.xz
$ make -j$(nproc) kernel/kheaders.o
DESCEND objtool
INSTALL libsubcmd_headers
CALL scripts/checksyscalls.sh
CHK kernel/kheaders_data.tar.xz
kernel/kheaders_data.tar.xz is not updated if steps [1] - [3] are run
within the same minute.
The headers_md5 variable stores the MD5 hash of the 'ls -l' output
for all header files. This hash value is used to determine whether
kheaders_data.tar.xz needs to be rebuilt. However, 'ls -l' prints the
modification times with minute-level granularity. If a file is modified
within the same minute and its size remains the same, the MD5 hash does
not change.
To reliably detect file modifications, this commit rewrites
kernel/gen_kheaders.sh to output header dependencies to
kernel/.kheaders_data.tar.xz.cmd. Then, Make compares the timestamps
and reruns kernel/gen_kheaders.sh when necessary. This is the standard
mechanism used by Make and Kbuild.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The second argument of bpf_sysctl_get_name() helper is a pointer to a
buffer that is being written to. However that isn't specify in the
prototype.
Until commit 37cce22dbd51a ("bpf: verifier: Refactor helper access
type tracking"), all helper accesses were considered as a possible
write access by the verifier, so no big harm was done. However, since
then, the verifier might make wrong asssumption about the content of
that address which might lead it to make faulty optimizations (such as
removing code that was wrongly labeled dead). This is what happens in
test_sysctl selftest to the tests related to sysctl_get_name.
Add MEM_WRITE flag the second argument of bpf_sysctl_get_name().
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250619140603.148942-2-jmarchan@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Fixes a minor spelling mistake in two comment lines
Signed-off-by: Ke Ma <makebit1999@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The last use of the work_on_cpu_safe() macro was removed recently by
commit 9cda46babdfe ("crypto: n2 - remove Niagara2 SPU driver")
Remove it, and the work_on_cpu_safe_key() function it calls.
Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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collect_mounts() has several problems - one can't iterate over the results
directly, so it has to be done with callback passed to iterate_mounts();
it has an oopsable race with d_invalidate(); it creates temporary clones
of mounts invisibly for sync umount (IOW, you can have non-lazy umount
succeed leaving filesystem not mounted anywhere and yet still busy).
A saner approach is to give caller an array of struct path that would pin
every mount in a subtree, without cloning any mounts.
* collect_mounts()/drop_collected_mounts()/iterate_mounts() is gone
* collect_paths(where, preallocated, size) gives either ERR_PTR(-E...) or
a pointer to array of struct path, one for each chunk of tree visible under
'where' (i.e. the first element is a copy of where, followed by (mount,root)
for everything mounted under it - the same set collect_mounts() would give).
Unlike collect_mounts(), the mounts are *not* cloned - we just get pinning
references to the roots of subtrees in the caller's namespace.
Array is terminated by {NULL, NULL} struct path. If it fits into
preallocated array (on-stack, normally), that's where it goes; otherwise
it's allocated by kmalloc_array(). Passing 0 as size means that 'preallocated'
is ignored (and expected to be NULL).
* drop_collected_paths(paths, preallocated) is given the array returned
by an earlier call of collect_paths() and the preallocated array passed to that
call. All mount/dentry references are dropped and array is kfree'd if it's not
equal to 'preallocated'.
* instead of iterate_mounts(), users should just iterate over array
of struct path - nothing exotic is needed for that. Existing users (all in
audit_tree.c) are converted.
[folded a fix for braino reported by Venkat Rao Bagalkote <venkat88@linux.ibm.com>]
Fixes: 80b5dce8c59b0 ("vfs: Add a function to lazily unmount all mounts from any dentry")
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Add a waitqueue helper to add a priority waiter that requires exclusive
wakeups, i.e. that requires that it be the _only_ priority waiter. The
API will be used by KVM to ensure that at most one of KVM's irqfds is
bound to a single eventfd (across the entire kernel).
Open code the helper instead of using __add_wait_queue() so that the
common path doesn't need to "handle" impossible failures.
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250522235223.3178519-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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Drop the setting of WQ_FLAG_EXCLUSIVE from add_wait_queue_priority() and
instead have callers manually add the flag prior to adding their structure
to the queue. Blindly setting WQ_FLAG_EXCLUSIVE is flawed, as the nature
of exclusive, priority waiters means that only the first waiter added will
ever receive notifications.
Pushing the flawed behavior to callers will allow fixing the problem one
hypervisor at a time (KVM added the flawed API, and then KVM's code was
copy+pasted nearly verbatim by Xen and Hyper-V), and will also allow for
adding an API that provides true exclusivity, i.e. that guarantees at most
one priority waiter is in the queue.
Opportunistically add a comment in Hyper-V to call out the mess. Xen
privcmd's irqfd_wakefup() doesn't actually operate in exclusive mode, i.e.
can be "fixed" simply by dropping WQ_FLAG_EXCLUSIVE. And KVM is primed to
switch to the aforementioned fully exclusive API, i.e. won't be carrying
the flawed code for long.
No functional change intended.
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250522235223.3178519-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
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The function update_prog_stats() will be called in the bpf trampoline.
In most cases, it will be optimized by the compiler by making it inline.
However, we can't rely on the compiler all the time, and just make it
__always_inline to reduce the possible overhead.
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Link: https://lore.kernel.org/r/20250621045501.101187-1-dongml2@chinatelecom.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton:
"20 hotfixes. 7 are cc:stable and the remainder address post-6.15
issues or aren't considered necessary for -stable kernels. Only 4 are
for MM.
- The series `Revert "bcache: update min_heap_callbacks to use
default builtin swap"' from Kuan-Wei Chiu backs out the author's
recent min_heap changes due to a performance regression.
A fix for this regression has been developed but we felt it best to
go back to the known-good version to give the new code more bake
time.
- A lot of MAINTAINERS maintenance.
I like to get these changes upstreamed promptly because they can't
break things and more accurate/complete MAINTAINERS info hopefully
improves the speed and accuracy of our responses to submitters and
reporters"
* tag 'mm-hotfixes-stable-2025-06-22-18-52' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
MAINTAINERS: add additional mmap-related files to mmap section
MAINTAINERS: add memfd, shmem quota files to shmem section
MAINTAINERS: add stray rmap file to mm rmap section
MAINTAINERS: add hugetlb_cgroup.c to hugetlb section
MAINTAINERS: add further init files to mm init block
MAINTAINERS: update maintainers for HugeTLB
maple_tree: fix MA_STATE_PREALLOC flag in mas_preallocate()
MAINTAINERS: add missing test files to mm gup section
MAINTAINERS: add missing mm/workingset.c file to mm reclaim section
selftests/mm: skip uprobe vma merge test if uprobes are not enabled
bcache: remove unnecessary select MIN_HEAP
Revert "bcache: remove heap-related macros and switch to generic min_heap"
Revert "bcache: update min_heap_callbacks to use default builtin swap"
selftests/mm: add configs to fix testcase failure
kho: initialize tail pages for higher order folios properly
MAINTAINERS: add linux-mm@ list to Kexec Handover
mm: userfaultfd: fix race of userfaultfd_move and swap cache
mm/gup: revert "mm: gup: fix infinite loop within __get_longterm_locked"
selftests/mm: increase timeout from 180 to 900 seconds
mm/shmem, swap: fix softlockup with mTHP swapin
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Mark struct cgroup_subsys_state->cgroup as safe under RCU read lock. This
will enable accessing css->cgroup from a bpf css iterator.
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/20250623063854.1896364-4-song@kernel.org
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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BPF programs, such as LSM and sched_ext, would benefit from tags on
cgroups. One common practice to apply such tags is to set xattrs on
cgroupfs folders.
Introduce kfunc bpf_cgroup_read_xattr, which allows reading cgroup's
xattr.
Note that, we already have bpf_get_[file|dentry]_xattr. However, these
two APIs are not ideal for reading cgroupfs xattrs, because:
1) These two APIs only works in sleepable contexts;
2) There is no kfunc that matches current cgroup to cgroupfs dentry.
bpf_cgroup_read_xattr is generic and can be useful for many program
types. It is also safe, because it requires trusted or rcu protected
argument (KF_RCU). Therefore, we make it available to all program types.
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/20250623063854.1896364-3-song@kernel.org
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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We need the driver-core fixes that are in 6.16-rc3 into here as well
to build on top of.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq fixes from Borislav Petkov:
- Fix missing prototypes warnings
- Properly initialize work context when allocating it
- Remove a method tracking when managed interrupts are suspended during
hotplug, in favor of the code using a IRQ disable depth tracking now,
and have interrupts get properly enabled again on restore
- Make sure multiple CPUs getting hotplugged don't cause wrong tracking
of the managed IRQ disable depth
* tag 'irq_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqchip/ath79-misc: Fix missing prototypes warnings
genirq/irq_sim: Initialize work context pointers properly
genirq/cpuhotplug: Restore affinity even for suspended IRQ
genirq/cpuhotplug: Rebalance managed interrupts across multi-CPU hotplug
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Borislav Petkov:
- Avoid a crash on a heterogeneous machine where not all cores support
the same hw events features
- Avoid a deadlock when throttling events
- Document the perf event states more
- Make sure a number of perf paths switching off or rescheduling events
call perf_cgroup_event_disable()
- Make sure perf does task sampling before its userspace mapping is
torn down, and not after
* tag 'perf_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel: Fix crash in icl_update_topdown_event()
perf: Fix the throttle error of some clock events
perf: Add comment to enum perf_event_state
perf/core: Fix WARN in perf_cgroup_switch()
perf: Fix dangling cgroup pointer in cpuctx
perf: Fix cgroup state vs ERROR
perf: Fix sample vs do_exit()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Borislav Petkov:
- Make sure the switch to the global hash is requested always under a
lock so that two threads requesting that simultaneously cannot get to
inconsistent state
- Reject negative NUMA nodes earlier in the futex NUMA interface
handling code
- Selftests fixes
* tag 'locking_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Verify under the lock if hash can be replaced
futex: Handle invalid node numbers supplied by user
selftests/futex: Set the home_node in futex_numa_mpol
selftests/futex: getopt() requires int as return value.
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From 077814f57f8acce13f91dc34bbd2b7e4911fbf25 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Fri, 13 Jun 2025 15:06:47 -1000
- Add CONFIG_GROUP_SCHED_BANDWIDTH which is selected by both
CONFIG_CFS_BANDWIDTH and EXT_GROUP_SCHED.
- Put bandwidth control interface files for both cgroup v1 and v2 under
CONFIG_GROUP_SCHED_BANDWIDTH.
- Update tg_bandwidth() to fetch configuration parameters from fair if
CONFIG_CFS_BANDWIDTH, SCX otherwise.
- Update tg_set_bandwidth() to update the parameters for both fair and SCX.
- Add bandwidth control parameters to struct scx_cgroup_init_args.
- Add sched_ext_ops.cgroup_set_bandwidth() which is invoked on bandwidth
control parameter updates.
- Update scx_qmap and maximal selftest to test the new feature.
Signed-off-by: Tejun Heo <tj@kernel.org>
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More sched_ext fields will be added to struct task_group. In preparation,
factor out sched_ext fields into struct scx_task_group to reduce clutter in
the common header. No functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull sched_ext/for-6.16-fixes to receive:
c50784e99f0e ("sched_ext: Make scx_group_set_weight() always update tg->scx.weight")
33796b91871a ("sched_ext, sched/core: Don't call scx_group_set_weight() prematurely from sched_create_group()")
which are needed to implement CPU bandwidth control interface support.
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into for-6.17
Pull tip/sched/core to receive the following commits:
d403a3689af5 ("sched/fair: Move max_cfs_quota_period decl and default_cfs_period() def from fair.c to sched.h")
de4c80c6963e ("sched/core: Relocate tg_get_cfs_*() and cpu_cfs_*_read_*()")
43e33f53e256 ("sched/core: Reorganize cgroup bandwidth control interface file reads")
5bc34be478d0 ("sched/core: Reorganize cgroup bandwidth control interface file writes")
These will be used to implement CPU bandwidth interface support in
sched_ext.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently the call_rcu() API does not check whether a callback
pointer is NULL. If NULL is passed, rcu_core() will try to invoke
it, resulting in NULL pointer dereference and a kernel crash.
To prevent this and improve debuggability, this patch adds a check
for NULL and emits a kernel stack trace to help identify a faulty
caller.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
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Currently, when restoring higher order folios, kho_restore_folio() only
calls prep_compound_page() on all the pages. That is not enough to
properly initialize the folios. The managed page count does not get
updated, the reserved flag does not get dropped, and page count does not
get initialized properly.
Restoring a higher order folio with it results in the following BUG with
CONFIG_DEBUG_VM when attempting to free the folio:
BUG: Bad page state in process test pfn:104e2b
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffffffffffffffff pfn:0x104e2b
flags: 0x2fffff80000000(node=0|zone=2|lastcpupid=0x1fffff)
raw: 002fffff80000000 0000000000000000 00000000ffffffff 0000000000000000
raw: ffffffffffffffff 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: nonzero _refcount
[...]
Call Trace:
<TASK>
dump_stack_lvl+0x4b/0x70
bad_page.cold+0x97/0xb2
__free_frozen_pages+0x616/0x850
[...]
Combine the path for 0-order and higher order folios, initialize the tail
pages with a count of zero, and call adjust_managed_page_count() to
account for all the pages instead of just missing them.
In addition, since all the KHO-preserved pages get marked with
MEMBLOCK_RSRV_NOINIT by deserialize_bitmap(), the reserved flag is not
actually set (as can also be seen from the flags of the dumped page in the
logs above). So drop the ClearPageReserved() calls.
[ptyadav@amazon.de: declare i in the loop instead of at the top]
Link: https://lkml.kernel.org/r/20250613125916.39272-1-pratyush@kernel.org
Link: https://lkml.kernel.org/r/20250605171143.76963-1-pratyush@kernel.org
Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation")
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Use ktime_get_ntp_seconds() to prepare for auxiliary clocks so that
the readout becomes per timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250519083026.472512636@linutronix.de
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Persist exit and coredump information independent of whether anyone
currently holds a pidfd for the struct pid.
The current scheme allocated pidfs dentries on-demand repeatedly.
This scheme is reaching it's limits as it makes it impossible to pin
information that needs to be available after the task has exited or
coredumped and that should not be lost simply because the pidfd got
closed temporarily. The next opener should still see the stashed
information.
This is also a prerequisite for supporting extended attributes on
pidfds to allow attaching meta information to them.
If someone opens a pidfd for a struct pid a pidfs dentry is allocated
and stashed in pid->stashed. Once the last pidfd for the struct pid is
closed the pidfs dentry is released and removed from pid->stashed.
So if 10 callers create a pidfs dentry for the same struct pid
sequentially, i.e., each closing the pidfd before the other creates a
new one then a new pidfs dentry is allocated every time.
Because multiple tasks acquiring and releasing a pidfd for the same
struct pid can race with each another a task may still find a valid
pidfs entry from the previous task in pid->stashed and reuse it. Or it
might find a dead dentry in there and fail to reuse it and so stashes a
new pidfs dentry. Multiple tasks may race to stash a new pidfs dentry
but only one will succeed, the other ones will put their dentry.
The current scheme aims to ensure that a pidfs dentry for a struct pid
can only be created if the task is still alive or if a pidfs dentry
already existed before the task was reaped and so exit information has
been was stashed in the pidfs inode.
That's great except that it's buggy. If a pidfs dentry is stashed in
pid->stashed after pidfs_exit() but before __unhash_process() is called
we will return a pidfd for a reaped task without exit information being
available.
The pidfds_pid_valid() check does not guard against this race as it
doens't sync at all with pidfs_exit(). The pid_has_task() check might be
successful simply because we're before __unhash_process() but after
pidfs_exit().
Introduce a new scheme where the lifetime of information associated with
a pidfs entry (coredump and exit information) isn't bound to the
lifetime of the pidfs inode but the struct pid itself.
The first time a pidfs dentry is allocated for a struct pid a struct
pidfs_attr will be allocated which will be used to store exit and
coredump information.
If all pidfs for the pidfs dentry are closed the dentry and inode can be
cleaned up but the struct pidfs_attr will stick until the struct pid
itself is freed. This will ensure minimal memory usage while persisting
relevant information.
The new scheme has various advantages. First, it allows to close the
race where we end up handing out a pidfd for a reaped task for which no
exit information is available. Second, it minimizes memory usage.
Third, it allows to remove complex lifetime tracking via dentries when
registering a struct pid with pidfs. There's no need to get or put a
reference. Instead, the lifetime of exit and coredump information
associated with a struct pid is bound to the lifetime of struct pid
itself.
Link: https://lore.kernel.org/20250618-work-pidfs-persistent-v2-5-98f3456fd552@kernel.org
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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ntp_adjtimex() requires access to the actual time keeper per timekeeper
ID. Provide an interface.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250519083026.411809421@linutronix.de
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Provide timekeepers for auxiliary clocks and initialize them during
boot.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.350061049@linutronix.de
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In preparation for supporting independent auxiliary timekeepers, add a
clock valid field and set it to true for the system timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.287145536@linutronix.de
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Don't invoke the VDSO and paravirt updates when utilized for auxiliary
clocks. This is a temporary workaround until the VDSO and paravirt
interfaces have been worked out.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250519083026.223876435@linutronix.de
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In __timekeeping_advance() the pointer to struct tk_data is hardcoded by the
use of &tk_core. As long as there is only a single timekeeper (tk_core),
this is not a problem. But when __timekeeping_advance() will be reused for
per auxiliary timekeepers, __timekeeping_advance() needs to be generalized.
Add a pointer to struct tk_data as function argument of
__timekeeping_advance() and adapt all call sites.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.160967312@linutronix.de
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Clean up the name space. No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.095637820@linutronix.de
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In preparation for supporting auxiliary POSIX clocks, add a timekeeper ID
to the relevant functions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083026.032425931@linutronix.de
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If auxiliary clocks are enabled, provide an array of NTP data so that the
auxiliary timekeepers can be steered independently of the core timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.969000914@linutronix.de
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To support auxiliary timekeeping and the related user space interfaces,
it's required to define a clock ID range for them.
Reserve 8 auxiliary clock IDs after the regular timekeeping clock ID space.
This is the maximum number of auxiliary clocks the kernel can support. The actual
number of supported clocks depends obviously on the presence of related devices
and might be constraint by the available VDSO space.
Add the corresponding timekeeper IDs as well.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.905800695@linutronix.de
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As long as there is only a single timekeeper, there is no need to clarify
which timekeeper is used. But with the upcoming reusage of the timekeeper
infrastructure for auxiliary clock timekeepers, an ID is required to
differentiate.
Introduce an enum for timekeeper IDs, introduce a field in struct tk_data
to store this timekeeper id and add also initialization. The id struct
field is added at the end of the second cachline, as there is a 4 byte hole
anyway.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.842476378@linutronix.de
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Consolidate do_adjtimex() so that it does not notify about clock changes
twice.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250519083025.779267274@linutronix.de
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.715836017@linutronix.de
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This was overlooked in the initial conversion. Use the provided pointer to
access the shadow timekeeper.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20250519083025.652611452@linutronix.de
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BPF_MAP_TYPE_LRU_HASH can recycle most recent elements well before the
map is full, due to percpu reservations and force shrink before
neighbor stealing. Once a CPU is unable to borrow from the global map,
it will once steal one elem from a neighbor and after that each time
flush this one element to the global list and immediately recycle it.
Batch value LOCAL_FREE_TARGET (128) will exhaust a 10K element map
with 79 CPUs. CPU 79 will observe this behavior even while its
neighbors hold 78 * 127 + 1 * 15 == 9921 free elements (99%).
CPUs need not be active concurrently. The issue can appear with
affinity migration, e.g., irqbalance. Each CPU can reserve and then
hold onto its 128 elements indefinitely.
Avoid global list exhaustion by limiting aggregate percpu caches to
half of map size, by adjusting LOCAL_FREE_TARGET based on cpu count.
This change has no effect on sufficiently large tables.
Similar to LOCAL_NR_SCANS and lru->nr_scans, introduce a map variable
lru->free_target. The extra field fits in a hole in struct bpf_lru.
The cacheline is already warm where read in the hot path. The field is
only accessed with the lru lock held.
Tested-by: Anton Protopopov <a.s.protopopov@gmail.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://lore.kernel.org/r/20250618215803.3587312-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fix from Tejun Heo:
- In cgroup1 freezer, a task migrating into a frozen cgroup might not
get frozen immediately due to the wrong operation order. Fix it.
* tag 'cgroup-for-6.16-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup,freezer: fix incomplete freezing when attaching tasks
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue fix from Tejun Heo:
- Fix missed early init of wq_isolated_cpumask
* tag 'wq-for-6.16-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Initialize wq_isolated_cpumask in workqueue_init_early()
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
Pull sched_ext fixes from Tejun Heo:
- Fix a couple bugs in cgroup cpu.weight support
- Add the new sched-ext@lists.linux.dev to MAINTAINERS
* tag 'sched_ext-for-6.16-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext, sched/core: Don't call scx_group_set_weight() prematurely from sched_create_group()
sched_ext: Make scx_group_set_weight() always update tg->scx.weight
sched_ext: Update mailing list entry in MAINTAINERS
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An issue was found:
# cd /sys/fs/cgroup/freezer/
# mkdir test
# echo FROZEN > test/freezer.state
# cat test/freezer.state
FROZEN
# sleep 1000 &
[1] 863
# echo 863 > test/cgroup.procs
# cat test/freezer.state
FREEZING
When tasks are migrated to a frozen cgroup, the freezer fails to
immediately freeze the tasks, causing the cgroup to remain in the
"FREEZING".
The freeze_task() function is called before clearing the CGROUP_FROZEN
flag. This causes the freezing() check to incorrectly return false,
preventing __freeze_task() from being invoked for the migrated task.
To fix this issue, clear the CGROUP_FROZEN state before calling
freeze_task().
Fixes: f5d39b020809 ("freezer,sched: Rewrite core freezer logic")
Cc: stable@vger.kernel.org # v6.1+
Reported-by: Zhong Jiawei <zhongjiawei1@huawei.com>
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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