From: Peter Zijlstra Date: Mon, 26 Oct 2020 15:22:56 +0000 (+0100) Subject: locking/lockdep: Remove more raw_cpu_read() usage X-Git-Tag: v5.10-rc2~4^2~1 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=d48e3850030623e1c20785bceaaf78f916d0b1a3;p=thirdparty%2Flinux.git 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) Link: https://lkml.kernel.org/r/20201026152256.GB2651@hirez.programming.kicks-ass.net --- diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index fc206aefa9708..11028497d4df7 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)