user/sven/linux.git/include/linux/lockdep.h, branch v5.4.36

locking/lockdep: Reduce space occupied by stack traces

2019-07-25T13:43:27Z

Although commit 669de8bda87b ("kernel/workqueue: Use dynamic lockdep keys for workqueues") unregisters dynamic lockdep keys when a workqueue is destroyed, a side effect of that commit is that all stack traces associated with the lockdep key are leaked when a workqueue is destroyed. Fix this by storing each unique stack trace once. Other changes in this patch are: - Use NULL instead of { .nr_entries = 0 } to represent 'no trace'. - Store a pointer to a stack trace in struct lock_class and struct lock_list instead of storing 'nr_entries' and 'offset'. This patch avoids that the following program triggers the "BUG: MAX_STACK_TRACE_ENTRIES too low!" complaint: #include #include int main() { for (;;) { int fd = open("/dev/infiniband/rdma_cm", O_RDWR); close(fd); } } Suggested-by: Peter Zijlstra Reported-by: Eric Biggers Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Cc: Yuyang Du Link: https://lkml.kernel.org/r/20190722182443.216015-4-bvanassche@acm.org Signed-off-by: Ingo Molnar

locking/lockdep: Make it clear that what lock_class::key points at is not modified

2019-07-25T13:43:26Z

This patch does not change the behavior of the lockdep code. Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Link: https://lkml.kernel.org/r/20190722182443.216015-2-bvanassche@acm.org Signed-off-by: Ingo Molnar

docs: locking: convert docs to ReST and rename to *.rst

2019-07-15T11:53:27Z

Convert the locking documents to ReST and add them to the kernel development book where it belongs. Most of the stuff here is just to make Sphinx to properly parse the text file, as they're already in good shape, not requiring massive changes in order to be parsed. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab Acked-by: Federico Vaga

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-07-08T23:12:03Z

Pull locking updates from Ingo Molnar: "The main changes in this cycle are: - rwsem scalability improvements, phase #2, by Waiman Long, which are rather impressive: "On a 2-socket 40-core 80-thread Skylake system with 40 reader and writer locking threads, the min/mean/max locking operations done in a 5-second testing window before the patchset were: 40 readers, Iterations Min/Mean/Max = 1,807/1,808/1,810 40 writers, Iterations Min/Mean/Max = 1,807/50,344/151,255 After the patchset, they became: 40 readers, Iterations Min/Mean/Max = 30,057/31,359/32,741 40 writers, Iterations Min/Mean/Max = 94,466/95,845/97,098" There's a lot of changes to the locking implementation that makes it similar to qrwlock, including owner handoff for more fair locking. Another microbenchmark shows how across the spectrum the improvements are: "With a locking microbenchmark running on 5.1 based kernel, the total locking rates (in kops/s) on a 2-socket Skylake system with equal numbers of readers and writers (mixed) before and after this patchset were: # of Threads Before Patch After Patch ------------ ------------ ----------- 2 2,618 4,193 4 1,202 3,726 8 802 3,622 16 729 3,359 32 319 2,826 64 102 2,744" The changes are extensive and the patch-set has been through several iterations addressing various locking workloads. There might be more regressions, but unless they are pathological I believe we want to use this new implementation as the baseline going forward. - jump-label optimizations by Daniel Bristot de Oliveira: the primary motivation was to remove IPI disturbance of isolated RT-workload CPUs, which resulted in the implementation of batched jump-label updates. Beyond the improvement of the real-time characteristics kernel, in one test this patchset improved static key update overhead from 57 msecs to just 1.4 msecs - which is a nice speedup as well. - atomic64_t cross-arch type cleanups by Mark Rutland: over the last ~10 years of atomic64_t existence the various types used by the APIs only had to be self-consistent within each architecture - which means they became wildly inconsistent across architectures. Mark puts and end to this by reworking all the atomic64 implementations to use 's64' as the base type for atomic64_t, and to ensure that this type is consistently used for parameters and return values in the API, avoiding further problems in this area. - A large set of small improvements to lockdep by Yuyang Du: type cleanups, output cleanups, function return type and othr cleanups all around the place. - A set of percpu ops cleanups and fixes by Peter Zijlstra. - Misc other changes - please see the Git log for more details" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (82 commits) locking/lockdep: increase size of counters for lockdep statistics locking/atomics: Use sed(1) instead of non-standard head(1) option locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING x86/jump_label: Make tp_vec_nr static x86/percpu: Optimize raw_cpu_xchg() x86/percpu, sched/fair: Avoid local_clock() x86/percpu, x86/irq: Relax {set,get}_irq_regs() x86/percpu: Relax smp_processor_id() x86/percpu: Differentiate this_cpu_{}() and __this_cpu_{}() locking/rwsem: Guard against making count negative locking/rwsem: Adaptive disabling of reader optimistic spinning locking/rwsem: Enable time-based spinning on reader-owned rwsem locking/rwsem: Make rwsem->owner an atomic_long_t locking/rwsem: Enable readers spinning on writer locking/rwsem: Clarify usage of owner's nonspinaable bit locking/rwsem: Wake up almost all readers in wait queue locking/rwsem: More optimal RT task handling of null owner locking/rwsem: Always release wait_lock before waking up tasks locking/rwsem: Implement lock handoff to prevent lock starvation locking/rwsem: Make rwsem_spin_on_owner() return owner state ...

locking/lockdep: Rename lockdep_assert_held_exclusive() -> lockdep_assert_held_write()

2019-06-17T10:09:24Z

All callers of lockdep_assert_held_exclusive() use it to verify the correct locking state of either a semaphore (ldisc_sem in tty, mmap_sem for perf events, i_rwsem of inode for dax) or rwlock by apparmor. Thus it makes sense to rename _exclusive to _write since that's the semantics callers care. Additionally there is already lockdep_assert_held_read(), which this new naming is more consistent with. No functional changes. Signed-off-by: Nikolay Borisov Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190531100651.3969-1-nborisov@suse.com Signed-off-by: Ingo Molnar

locking/lockdep: Change the range of class_idx in held_lock struct

2019-06-03T09:55:43Z

held_lock->class_idx is used to point to the class of the held lock. The index is shifted by 1 to make index 0 mean no class, which results in class index shifting back and forth but is not worth doing so. The reason is: (1) there will be no "no-class" held_lock to begin with, and (2) index 0 seems to be used for error checking, but if something wrong indeed happened, the index can't be counted on to distinguish it as that something won't set the class_idx to 0 on purpose to tell us it is wrong. Therefore, change the index to start from 0. This saves a lot of back-and-forth shifts and a class slot back to lock_classes. Since index 0 is now used for lock class, we change the initial chain key to -1 to avoid key collision, which is due to the fact that __jhash_mix(0, 0, 0) = 0. Actually, the initial chain key can be any arbitrary value other than 0. In addition, a bitmap is maintained to keep track of the used lock classes, and we check the validity of the held lock against that bitmap. Signed-off-by: Yuyang Du Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bvanassche@acm.org Cc: frederic@kernel.org Cc: ming.lei@redhat.com Cc: will.deacon@arm.com Link: https://lkml.kernel.org/r/20190506081939.74287-10-duyuyang@gmail.com Signed-off-by: Ingo Molnar

locking/lockdep: Define INITIAL_CHAIN_KEY for chain keys to start with

2019-06-03T09:55:43Z

Chain keys are computed using Jenkins hash function, which needs an initial hash to start with. Dedicate a macro to make this clear and configurable. A later patch changes this initial chain key. Signed-off-by: Yuyang Du Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bvanassche@acm.org Cc: frederic@kernel.org Cc: ming.lei@redhat.com Cc: will.deacon@arm.com Link: https://lkml.kernel.org/r/20190506081939.74287-9-duyuyang@gmail.com Signed-off-by: Ingo Molnar

locking/lockdep: Use lockdep_init_task for task initiation consistently

2019-06-03T09:55:42Z

Despite that there is a lockdep_init_task() which does nothing, lockdep initiates tasks by assigning lockdep fields and does so inconsistently. Fix this by using lockdep_init_task(). Signed-off-by: Yuyang Du Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bvanassche@acm.org Cc: frederic@kernel.org Cc: ming.lei@redhat.com Cc: will.deacon@arm.com Link: https://lkml.kernel.org/r/20190506081939.74287-8-duyuyang@gmail.com Signed-off-by: Ingo Molnar

locking/lockdep: Update obsolete struct field description

2019-06-03T09:55:41Z

The lock_chain struct definition has outdated comment, update it and add struct member description. Signed-off-by: Yuyang Du Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: bvanassche@acm.org Cc: frederic@kernel.org Cc: ming.lei@redhat.com Cc: will.deacon@arm.com Link: https://lkml.kernel.org/r/20190506081939.74287-7-duyuyang@gmail.com Signed-off-by: Ingo Molnar

lockdep: Add assertion to check if in an interrupt

2019-05-25T21:50:51Z

In rcu_rrupt_from_idle, we want to check if it is called from within an interrupt, but want to do such checking only for debug builds. lockdep already tracks when we enter an interrupt. Let us expose it as an assertion macro so it can be used to assert this. Suggested-by: Steven Rostedt Cc: kernel-team@android.com Cc: rcu@vger.kernel.org Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney