The following commit has been merged into the locking/urgent branch of tip: Commit-ID: d48e3850030623e1c20785bceaaf78f916d0b1a3 Gitweb: https://git.kernel.org/tip/d48e3850030623e1c20785bceaaf78f916d0b1a3 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Mon, 26 Oct 2020 16:22:56 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 30 Oct 2020 17:07:18 +01:00 locking/lockdep: Remove more raw_cpu_read() usage I initially thought raw_cpu_read() was OK, since if it is !0 we have IRQs disabled and can't get migrated, so if we get migrated both CPUs must have 0 and it doesn't matter which 0 we read. And while that is true; it isn't the whole store, on pretty much all architectures (except x86) this can result in computing the address for one CPU, getting migrated, the old CPU continuing execution with another task (possibly setting recursion) and then the new CPU reading the value of the old CPU, which is no longer 0. Similer to: baffd723e44d ("lockdep: Revert "lockdep: Use raw_cpu_*() for per-cpu variables"") Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20201026152256.GB2651@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx --- kernel/locking/lockdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index fc206ae..1102849 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -84,7 +84,7 @@ static inline bool lockdep_enabled(void) if (!debug_locks) return false; - if (raw_cpu_read(lockdep_recursion)) + if (this_cpu_read(lockdep_recursion)) return false; if (current->lockdep_recursion)
![]() |