The WW-mutex selftests deliberately exercise failing lock paths. On
PREEMPT_RT, some of those paths enter the RT-mutex scheduler helpers.
The change referenced by the Fixes tag made those helpers track RT-mutex
scheduling state in current->sched_rt_mutex. The bit is normally cleared by
the matching post-schedule helper, but some WW-mutex selftests disable
the runtime debug_locks flag before that happens. With debug_locks cleared,
lockdep_assert() does not evaluate the expression that clears the bit,
leaving stale state for the next testcase.
With CONFIG_PREEMPT_RT=y and CONFIG_DEBUG_LOCKING_API_SELFTESTS=y, that
stale state produces warnings such as:
WARNING: kernel/sched/core.c:7557 at rt_mutex_pre_schedule+0x26/0x2d
RIP: 0010:rt_mutex_pre_schedule+0x26/0x2d
Save and restore current->sched_rt_mutex around each testcase, matching the
existing PREEMPT_RT cleanup for task-local migration and RCU state.
Fixes: d14f9e930b ("locking/rtmutex: Use rt_mutex specific scheduler helpers")
Assisted-by: Codex:gpt-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260523185123.17482-3-kmehltretter@gmail.com
The lockdep selftests deliberately run unbalanced locking patterns.
dotest() restores the task state they leave behind before running the
next testcase.
On PREEMPT_RT, spin_lock() uses migrate_disable() instead of disabling
preemption. dotest() cleans up the resulting migration-disabled state, but
that cleanup is still guarded by CONFIG_SMP.
That used to match the scheduler data model, where migration_disabled was
also CONFIG_SMP-only. The commit referenced below made SMP scheduler state
unconditional, so CONFIG_SMP=n PREEMPT_RT kernels with
CONFIG_DEBUG_LOCKING_API_SELFTESTS=y report success from the selftests and
then trip over stale current->migration_disabled state:
releasing a pinned lock
bad: scheduling from the idle thread!
Kernel panic - not syncing: Fatal exception
Save and restore current->migration_disabled for every PREEMPT_RT build.
Fixes: cac5cefbad ("sched/smp: Make SMP unconditional")
Assisted-by: Codex:gpt-5
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260523185123.17482-2-kmehltretter@gmail.com
The "__cleanup__" attribute is already used for wait context tests, so
using it for locking tests has already been proven working. Now since
SBRM APIs are merged, let's use these APIs instead of a local guard
framework. This also helps testing SBRM APIs.
Note that originally the tests don't rely on the cleanup ordering of
two variables in the same scope, but since now it's something we'd like
to assume and rely on[1], drop the extra scope in inner_in_outer()
function. Again this gives us another opportunity to test the compiler
behavior.
[1]: https://lore.kernel.org/lkml/CAHk-=whEsr6fuVSdsoNPokLR2fZiGuo_hCLyrS-LCw7hT_N7cQ@mail.gmail.com/
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230715235257.110325-1-boqun.feng@gmail.com
The ww-mutex selftest operates directly on ww_mutex::base and assumes
its type is struct mutex. This isn't true on PREEMPT_RT which turns the
mutex into a rtmutex.
Add a ww_mutex_base_ abstraction which maps to the relevant mutex_ or
rt_mutex_ function.
Change the CONFIG_DEBUG_MUTEXES ifdef to DEBUG_WW_MUTEXES. The latter is
true for the MUTEX and RTMUTEX implementation of WW-MUTEX. The
assignment is required in order to pass the tests.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-10-bigeasy@linutronix.de
The softirq context on PREEMPT_RT is different compared to !PREEMPT_RT.
As such lockdep_softirq_enter() is a nop and the all the "softirq safe"
tests fail on PREEMPT_RT because there is no difference.
Skip the softirq context tests on PREEMPT_RT.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-9-bigeasy@linutronix.de
The tests with unbalanced lock() + unlock() operation leave a modified
preemption counter behind which is then reset to its original value
after the test.
The spin_lock() function on PREEMPT_RT does not include a
preempt_disable() statement but migrate_disable() and read_rcu_lock().
As a consequence both counter never get back to their original value
and the system explodes later after the selftest. In the
double-unlock case on PREEMPT_RT, the migrate_disable() and RCU code
will trigger a warning which should be avoided. These counter should
not be decremented below their initial value.
Save both counters and bring them back to their original value after
the test. In the double-unlock case, increment both counter in
advance to they become balanced after the double unlock.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-8-bigeasy@linutronix.de
i915 will soon gain an eviction path that trylock a whole lot of locks
for eviction, getting dmesg failures like below:
BUG: MAX_LOCK_DEPTH too low!
turning off the locking correctness validator.
depth: 48 max: 48!
48 locks held by i915_selftest/5776:
#0: ffff888101a79240 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x88/0x160
#1: ffffc900009778c0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_vma_pin.constprop.63+0x39/0x1b0 [i915]
#2: ffff88800cf74de8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_vma_pin.constprop.63+0x5f/0x1b0 [i915]
#3: ffff88810c7f9e38 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c4/0x9d0 [i915]
#4: ffff88810bad5768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915]
#5: ffff88810bad60e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915]
...
#46: ffff88811964d768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915]
#47: ffff88811964e0e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915]
INFO: lockdep is turned off.
Fixing eviction to nest into ww_class_acquire is a high priority, but
it requires a rework of the entire driver, which can only be done one
step at a time.
As an intermediate solution, add an acquire context to
ww_mutex_trylock, which allows us to do proper nesting annotations on
the trylocks, making the above lockdep splat disappear.
This is also useful in regulator_lock_nested, which may avoid dropping
regulator_nesting_mutex in the uncontended path, so use it there.
TTM may be another user for this, where we could lock a buffer in a
fastpath with list locks held, without dropping all locks we hold.
[peterz: rework actual ww_mutex_trylock() implementations]
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YUBGPdDDjKlxAuXJ@hirez.programming.kicks-ass.net
When PROVE_RAW_LOCK_NESTING=y many of the selftests FAILED because
HARDIRQ context is out-of-bounds for spinlocks. Instead make the
default hardware context the threaded hardirq context, which preserves
the old locking rules.
The wait-type specific locking selftests will have a non-threaded
HARDIRQ variant.
Fixes: de8f5e4f2d ("lockdep: Introduce wait-type checks")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20210617190313.322096283@infradead.org
These tests are added for two purposes:
* Test the implementation of wait context checks and related
annotations.
* Semi-document the rules for wait context nesting when
PROVE_RAW_LOCK_NESTING=y.
The test cases are only avaible for PROVE_RAW_LOCK_NESTING=y, as wait
context checking makes more sense for that configuration.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201208103112.2838119-5-boqun.feng@gmail.com
Merge misc updates from Andrew Morton:
- a few random little subsystems
- almost all of the MM patches which are staged ahead of linux-next
material. I'll trickle to post-linux-next work in as the dependents
get merged up.
Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (200 commits)
mm: cleanup kstrto*() usage
mm: fix fall-through warnings for Clang
mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
mm:backing-dev: use sysfs_emit in macro defining functions
mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
mm: use sysfs_emit for struct kobject * uses
mm: fix kernel-doc markups
zram: break the strict dependency from lzo
zram: add stat to gather incompressible pages since zram set up
zram: support page writeback
mm/process_vm_access: remove redundant initialization of iov_r
mm/zsmalloc.c: rework the list_add code in insert_zspage()
mm/zswap: move to use crypto_acomp API for hardware acceleration
mm/zswap: fix passing zero to 'PTR_ERR' warning
mm/zswap: make struct kernel_param_ops definitions const
userfaultfd/selftests: hint the test runner on required privilege
userfaultfd/selftests: fix retval check for userfaultfd_open()
userfaultfd/selftests: always dump something in modes
userfaultfd: selftests: make __{s,u}64 format specifiers portable
...
The selftest nests rwlock_t inside raw_spinlock_t, this is invalid.
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Add two self test cases for the following case:
P0: P1: P2:
<in irq handler>
spin_lock_irq(&slock) read_lock(&rwlock)
write_lock_irq(&rwlock)
read_lock(&rwlock) spin_lock(&slock)
, which is a deadlock, as the read_lock() on P0 cannot get the lock
because of the fairness.
P0: P1: P2:
<in irq handler>
spin_lock(&slock) read_lock(&rwlock)
write_lock(&rwlock)
read_lock(&rwlock) spin_lock_irq(&slock)
, which is not a deadlock, as the read_lock() on P0 can get the lock
because it could use the unfair fastpass.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-19-boqun.feng@gmail.com
Add those four test cases:
1. X --(ER)--> Y --(ER)--> Z --(ER)--> X is deadlock.
2. X --(EN)--> Y --(SR)--> Z --(ER)--> X is deadlock.
3. X --(EN)--> Y --(SR)--> Z --(SN)--> X is not deadlock.
4. X --(ER)--> Y --(SR)--> Z --(EN)--> X is not deadlock.
Those self testcases are valuable for the development of supporting
recursive read related deadlock detection.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-17-boqun.feng@gmail.com
