From 0302d2fd6efb0c386e521df0134eb2679a9a138f Mon Sep 17 00:00:00 2001 From: Thomas Hellström Date: Wed, 27 Nov 2024 09:54:30 +0100 Subject: locking/ww_mutex: Fix ww_mutex dummy lockdep map selftest warnings MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The below commit introduces a dummy lockdep map, but didn't get the initialization quite right (it should mimic the initialization of the real ww_mutex lockdep maps). It also introduced a separate locking api selftest failure. Fix these. Closes: https://lore.kernel.org/lkml/Zw19sMtnKdyOVQoh@boqun-archlinux/ Fixes: 823a566221a5 ("locking/ww_mutex: Adjust to lockdep nest_lock requirements") Reported-by: Boqun Feng Suggested-by: Boqun Feng Signed-off-by: Thomas Hellström Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241127085430.3045-1-thomas.hellstrom@linux.intel.com --- include/linux/ww_mutex.h | 4 ++-- lib/locking-selftest.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index a401a2f31a77..45ff6f7a872b 100644 --- a/include/linux/ww_mutex.h +++ b/include/linux/ww_mutex.h @@ -156,8 +156,8 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, &ww_class->acquire_key, 0); - lockdep_init_map(&ctx->first_lock_dep_map, ww_class->mutex_name, - &ww_class->mutex_key, 0); + lockdep_init_map_wait(&ctx->first_lock_dep_map, ww_class->mutex_name, + &ww_class->mutex_key, 0, LD_WAIT_SLEEP); mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx->dep_map, _RET_IP_); #endif diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 6e0c019f71b6..ed99344317f5 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -1720,8 +1720,6 @@ static void ww_test_normal(void) { int ret; - WWAI(&t); - /* * None of the ww_mutex codepaths should be taken in the 'normal' * mutex calls. The easiest way to verify this is by using the @@ -1770,6 +1768,8 @@ static void ww_test_normal(void) ww_mutex_base_unlock(&o.base); WARN_ON(o.ctx != (void *)~0UL); + WWAI(&t); + /* nest_lock */ o.ctx = (void *)~0UL; ww_mutex_base_lock_nest_lock(&o.base, &t); -- cgit v1.2.3-70-g09d2 From b4d83c8323b0c4a899a996fed919cfe10720d289 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 6 Dec 2024 10:19:31 +0100 Subject: headers/cleanup.h: Remove the if_not_guard() facility Linus noticed that the new if_not_guard() definition is fragile: "This macro generates actively wrong code if it happens to be inside an if-statement or a loop without a block. IOW, code like this: for (iterate-over-something) if_not_guard(a) return -BUSY; looks like will build fine, but will generate completely incorrect code." The reason is that the __if_not_guard() macro is multi-statement, so while most kernel developers expect macros to be simple or at least compound statements - but for __if_not_guard() it is not so: #define __if_not_guard(_name, _id, args...) \ BUILD_BUG_ON(!__is_cond_ptr(_name)); \ CLASS(_name, _id)(args); \ if (!__guard_ptr(_name)(&_id)) To add insult to injury, the placement of the BUILD_BUG_ON() line makes the macro appear to compile fine, but it will generate incorrect code as Linus reported, for example if used within iteration or conditional statements that will use the first statement of a macro as a loop body or conditional statement body. [ I'd also like to note that the original submission by David Lechner did not contain the BUILD_BUG_ON() line, so it was safer than what we ended up committing. Mea culpa. ] It doesn't appear to be possible to turn this macro into a robust single or compound statement that could be used in single statements, due to the necessity to define an auto scope variable with an open scope and the necessity of it having to expand to a partial 'if' statement with no body. Instead of trying to work around this fragility, just remove the construct before it gets used. Reported-by: Linus Torvalds Signed-off-by: Ingo Molnar Cc: David Lechner Cc: Peter Zijlstra Link: https://lore.kernel.org/r/Z1LBnX9TpZLR5Dkf@gmail.com --- include/linux/cleanup.h | 14 -------------- 1 file changed, 14 deletions(-) diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index 966fcc5ff8ef..ec00e3f7af2b 100644 --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -273,12 +273,6 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ * an anonymous instance of the (guard) class, not recommended for * conditional locks. * - * if_not_guard(name, args...) { }: - * convenience macro for conditional guards that calls the statement that - * follows only if the lock was not acquired (typically an error return). - * - * Only for conditional locks. - * * scoped_guard (name, args...) { }: * similar to CLASS(name, scope)(args), except the variable (with the * explicit name 'scope') is declard in a for-loop such that its scope is @@ -350,14 +344,6 @@ _label: \ #define scoped_cond_guard(_name, _fail, args...) \ __scoped_cond_guard(_name, _fail, __UNIQUE_ID(label), args) -#define __if_not_guard(_name, _id, args...) \ - BUILD_BUG_ON(!__is_cond_ptr(_name)); \ - CLASS(_name, _id)(args); \ - if (!__guard_ptr(_name)(&_id)) - -#define if_not_guard(_name, args...) \ - __if_not_guard(_name, __UNIQUE_ID(guard), args) - /* * Additional helper macros for generating lock guards with types, either for * locks that don't have a native type (eg. RCU, preempt) or those that need a -- cgit v1.2.3-70-g09d2