user/sven/linux.git/include/linux/lockdep.h, branch v5.10.1

Merge branch 'locking/urgent' into locking/core, to pick up fixes

2020-10-09T06:55:17Z

Signed-off-by: Ingo Molnar

lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"

2020-10-09T06:54:00Z

The thinking in commit: fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables") is flawed. While it is true that when we're migratable both CPUs will have a 0 value, it doesn't hold that when we do get migrated in the middle of a raw_cpu_op(), the old CPU will still have 0 by the time we get around to reading it on the new CPU. Luckily, the reason for that commit (s390 using preempt_disable() instead of preempt_disable_notrace() in their percpu code), has since been fixed by commit: 1196f12a2c96 ("s390: don't trace preemption in percpu macros") An audit of arch/*/include/asm/percpu*.h shows there are no other architectures affected by this particular issue. Fixes: fddf9055a60d ("lockdep: Use raw_cpu_*() for per-cpu variables") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20201005095958.GJ2651@hirez.programming.kicks-ass.net

lockdep: Fix lockdep recursion

2020-10-09T06:53:30Z

Steve reported that lockdep_assert*irq*(), when nested inside lockdep itself, will trigger a false-positive. One example is the stack-trace code, as called from inside lockdep, triggering tracing, which in turn calls RCU, which then uses lockdep_assert_irqs_disabled(). Fixes: a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables") Reported-by: Steven Rostedt Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar

lockdep: Extend __bfs() to work with multiple types of dependencies

2020-08-26T10:42:04Z

Now we have four types of dependencies in the dependency graph, and not all the pathes carry real dependencies (the dependencies that may cause a deadlock), for example: Given lock A and B, if we have: CPU1 CPU2 ============= ============== write_lock(A); read_lock(B); read_lock(B); write_lock(A); (assuming read_lock(B) is a recursive reader) then we have dependencies A -(ER)-> B, and B -(SN)-> A, and a dependency path A -(ER)-> B -(SN)-> A. In lockdep w/o recursive locks, a dependency path from A to A means a deadlock. However, the above case is obviously not a deadlock, because no one holds B exclusively, therefore no one waits for the other to release B, so who get A first in CPU1 and CPU2 will run non-blockingly. As a result, dependency path A -(ER)-> B -(SN)-> A is not a real/strong dependency that could cause a deadlock. From the observation above, we know that for a dependency path to be real/strong, no two adjacent dependencies can be as -(*R)-> -(S*)->. Now our mission is to make __bfs() traverse only the strong dependency paths, which is simple: we record whether we only have -(*R)-> for the previous lock_list of the path in lock_list::only_xr, and when we pick a dependency in the traverse, we 1) filter out -(S*)-> dependency if the previous lock_list only has -(*R)-> dependency (i.e. ->only_xr is true) and 2) set the next lock_list::only_xr to true if we only have -(*R)-> left after we filter out dependencies based on 1), otherwise, set it to false. With this extension for __bfs(), we now need to initialize the root of __bfs() properly (with a correct ->only_xr), to do so, we introduce some helper functions, which also cleans up a little bit for the __bfs() root initialization code. Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200807074238.1632519-8-boqun.feng@gmail.com

lockdep: Introduce lock_list::dep

2020-08-26T10:42:04Z

To add recursive read locks into the dependency graph, we need to store the types of dependencies for the BFS later. There are four types of dependencies: * Exclusive -> Non-recursive dependencies: EN e.g. write_lock(prev) held and try to acquire write_lock(next) or non-recursive read_lock(next), which can be represented as "prev -(EN)-> next" * Shared -> Non-recursive dependencies: SN e.g. read_lock(prev) held and try to acquire write_lock(next) or non-recursive read_lock(next), which can be represented as "prev -(SN)-> next" * Exclusive -> Recursive dependencies: ER e.g. write_lock(prev) held and try to acquire recursive read_lock(next), which can be represented as "prev -(ER)-> next" * Shared -> Recursive dependencies: SR e.g. read_lock(prev) held and try to acquire recursive read_lock(next), which can be represented as "prev -(SR)-> next" So we use 4 bits for the presence of each type in lock_list::dep. Helper functions and macros are also introduced to convert a pair of locks into lock_list::dep bit and maintain the addition of different types of dependencies. Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200807074238.1632519-7-boqun.feng@gmail.com

lockdep: Reduce the size of lock_list::distance

2020-08-26T10:42:04Z

lock_list::distance is always not greater than MAX_LOCK_DEPTH (which is 48 right now), so a u16 will fit. This patch reduces the size of lock_list::distance to save space, so that we can introduce other fields to help detect recursive read lock deadlocks without increasing the size of lock_list structure. Suggested-by: Peter Zijlstra Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200807074238.1632519-6-boqun.feng@gmail.com

locking: More accurate annotations for read_lock()

2020-08-26T10:42:02Z

On the archs using QUEUED_RWLOCKS, read_lock() is not always a recursive read lock, actually it's only recursive if in_interrupt() is true. So change the annotation accordingly to catch more deadlocks. Note we used to treat read_lock() as pure recursive read locks in lib/locking-seftest.c, and this is useful, especially for the lockdep development selftest, so we keep this via a variable to force switching lock annotation for read_lock(). Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200807074238.1632519-2-boqun.feng@gmail.com

lockdep: Use raw_cpu_*() for per-cpu variables

2020-08-26T10:41:53Z

Sven reported that commit a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables") caused trouble on s390 because their this_cpu_*() primitives disable preemption which then lands back tracing. On the one hand, per-cpu ops should use preempt_*able_notrace() and raw_local_irq_*(), on the other hand, we can trivialy use raw_cpu_*() ops for this. Fixes: a21ee6055c30 ("lockdep: Change hardirq{s_enabled,_context} to per-cpu variables") Reported-by: Sven Schnelle Reviewed-by: Steven Rostedt (VMware) Reviewed-by: Thomas Gleixner Acked-by: Rafael J. Wysocki Tested-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200821085348.192346882@infradead.org

locking/seqlock, headers: Untangle the spaghetti monster

2020-08-06T14:13:13Z

By using lockdep_assert_*() from seqlock.h, the spaghetti monster attacked. Attack back by reducing seqlock.h dependencies from two key high level headers: - : -Remove - : -Remove - : +Add The price was to add it to sched.h ... Core header fallout, we add direct header dependencies instead of gaining them parasitically from higher level headers: - : +Add - : +Add - : +Add - : +Add - : +Add - : +Add Arch headers fallout: - PARISC: : +Add - SH: : +Add - SPARC: : +Add - SPARC: : +Add , -Remove - X86: : +Add -Remove There's also a bunch of parasitic header dependency fallout in .c files, not listed separately. [ mingo: Extended the changelog, split up & fixed the original patch. ] Co-developed-by: Ingo Molnar Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200804133438.GK2674@hirez.programming.kicks-ass.net

lockdep: Add preemption enabled/disabled assertion APIs

2020-07-29T14:14:24Z

Asserting that preemption is enabled or disabled is a critical sanity check. Developers are usually reluctant to add such a check in a fastpath as reading the preemption count can be costly. Extend the lockdep API with macros asserting that preemption is disabled or enabled. If lockdep is disabled, or if the underlying architecture does not support kernel preemption, this assert has no runtime overhead. References: f54bb2ec02c8 ("locking/lockdep: Add IRQs disabled/enabled assertion APIs: ...") Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200720155530.1173732-8-a.darwish@linutronix.de