[PATCH 00/16] DEPT(Dependency Tracker)

Byungchul Park
2022-02-17T10:58:20Z

Hi Linus and folks,

I've been developing a tool for detecting deadlock possibilities by
tracking wait/event rather than lock(?) acquisition order to try to
cover all synchonization machanisms. It's done on v5.17-rc1 tag.

https://github.com/lgebyungchulpark/linux-dept/commits/dept1.12_on_v5.17-rc1

Benifit:

0. Works with all lock primitives.
1. Works with wait_for_completion()/complete().
2. Works with 'wait' on PG_locked.
3. Works with 'wait' on PG_writeback.
4. Works with swait/wakeup.
5. Works with waitqueue.
6. Multiple reports are allowed.
7. Deduplication control on multiple reports.
8. Withstand false positives thanks to 6.
9. Easy to tag any wait/event.

Future work:

0. To make it more stable.
1. To separates Dept from Lockdep.
2. To improves performance in terms of time and space.
3. To use Dept as a dependency engine for Lockdep.
4. To add any missing tags of wait/event in the kernel.
5. To deduplicate stack trace.

I've got several reports from the tool. Some of them look like false
alarms and some others look like real deadlock possibility. Because of
my unfamiliarity of the domain, it's hard to confirm if it's a real one.
Let me add the reports on this email thread.

How to interpret the report is:

1. E(event) in each context cannot be triggered because of the
W(wait) that cannot be woken.
2. The stack trace helping find the problematic code is located
in each conext's detail.

Changes from RFC:

1. Prevent adding a wait tag at prepare_to_wait() but __schedule().
2. Use try version at lockdep_acquire_cpus_lock() annotation.
3. Distinguish each syscall context from another.

Thanks,
Byungchul

Byungchul Park (16):
llist: Move llist_{head,node} definition to types.h
dept: Implement Dept(Dependency Tracker)
dept: Embed Dept data in Lockdep
dept: Apply Dept to spinlock
dept: Apply Dept to mutex families
dept: Apply Dept to rwlock
dept: Apply Dept to wait_for_completion()/complete()
dept: Apply Dept to seqlock
dept: Apply Dept to rwsem
dept: Add proc knobs to show stats and dependency graph
dept: Introduce split map concept and new APIs for them
dept: Apply Dept to wait/event of PG_{locked,writeback}
dept: Apply SDT to swait
dept: Apply SDT to wait(waitqueue)
locking/lockdep, cpu/hotplus: Use a weaker annotation in AP thread
dept: Distinguish each syscall context from another

include/linux/completion.h | 42 +-
include/linux/dept.h | 523 +++++++
include/linux/dept_page.h | 78 ++
include/linux/dept_sdt.h | 62 +
include/linux/hardirq.h | 3 +
include/linux/irqflags.h | 33 +-
include/linux/llist.h | 8 -
include/linux/lockdep.h | 156 ++-
include/linux/lockdep_types.h | 3 +
include/linux/mutex.h | 31 +
include/linux/page-flags.h | 45 +-
include/linux/pagemap.h | 7 +-
include/linux/percpu-rwsem.h | 10 +-
include/linux/rtmutex.h | 7 +
include/linux/rwlock.h | 48 +
include/linux/rwlock_api_smp.h | 8 +-
include/linux/rwlock_types.h | 7 +
include/linux/rwsem.h | 31 +
include/linux/sched.h | 7 +
include/linux/seqlock.h | 59 +-
include/linux/spinlock.h | 24 +
include/linux/spinlock_types_raw.h | 13 +
include/linux/swait.h | 4 +
include/linux/types.h | 8 +
include/linux/wait.h | 6 +-
init/init_task.c | 2 +
init/main.c | 4 +
kernel/Makefile | 1 +
kernel/cpu.c | 2 +-
kernel/dependency/Makefile | 5 +
kernel/dependency/dept.c | 2702 ++++++++++++++++++++++++++++++++++++
kernel/dependency/dept_hash.h | 10 +
kernel/dependency/dept_internal.h | 26 +
kernel/dependency/dept_object.h | 13 +
kernel/dependency/dept_proc.c | 93 ++
kernel/entry/common.c | 3 +
kernel/exit.c | 1 +
kernel/fork.c | 2 +
kernel/locking/lockdep.c | 12 +-
kernel/module.c | 2 +
kernel/sched/completion.c | 12 +-
kernel/sched/core.c | 3 +
kernel/sched/swait.c | 10 +
kernel/sched/wait.c | 16 +
kernel/softirq.c | 6 +-
kernel/trace/trace_preemptirq.c | 19 +-
lib/Kconfig.debug | 21 +
mm/filemap.c | 68 +
mm/page_ext.c | 5 +
49 files changed, 4204 insertions(+), 57 deletions(-)
create mode 100644 include/linux/dept.h
create mode 100644 include/linux/dept_page.h
create mode 100644 include/linux/dept_sdt.h
create mode 100644 kernel/dependency/Makefile
create mode 100644 kernel/dependency/dept.c
create mode 100644 kernel/dependency/dept_hash.h
create mode 100644 kernel/dependency/dept_internal.h
create mode 100644 kernel/dependency/dept_object.h
create mode 100644 kernel/dependency/dept_proc.c

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1.9.1