From e966eaeeb623f09975ef362c2866fae6f86844f9 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 12 Dec 2017 12:31:16 +0100 Subject: locking/lockdep: Remove the cross-release locking checks This code (CONFIG_LOCKDEP_CROSSRELEASE=y and CONFIG_LOCKDEP_COMPLETIONS=y), while it found a number of old bugs initially, was also causing too many false positives that caused people to disable lockdep - which is arguably a worse overall outcome. If we disable cross-release by default but keep the code upstream then in practice the most likely outcome is that we'll allow the situation to degrade gradually, by allowing entropy to introduce more and more false positives, until it overwhelms maintenance capacity. Another bad side effect was that people were trying to work around the false positives by uglifying/complicating unrelated code. There's a marked difference between annotating locking operations and uglifying good code just due to bad lock debugging code ... This gradual decrease in quality happened to a number of debugging facilities in the kernel, and lockdep is pretty complex already, so we cannot risk this outcome. Either cross-release checking can be done right with no false positives, or it should not be included in the upstream kernel. ( Note that it might make sense to maintain it out of tree and go through the false positives every now and then and see whether new bugs were introduced. ) Cc: Byungchul Park Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/completion.h | 45 --------------------------------------------- 1 file changed, 45 deletions(-) (limited to 'include/linux/completion.h') diff --git a/include/linux/completion.h b/include/linux/completion.h index 0662a417febe..94a59ba7d422 100644 --- a/include/linux/completion.h +++ b/include/linux/completion.h @@ -10,9 +10,6 @@ */ #include -#ifdef CONFIG_LOCKDEP_COMPLETIONS -#include -#endif /* * struct completion - structure used to maintain state for a "completion" @@ -29,58 +26,16 @@ struct completion { unsigned int done; wait_queue_head_t wait; -#ifdef CONFIG_LOCKDEP_COMPLETIONS - struct lockdep_map_cross map; -#endif }; -#ifdef CONFIG_LOCKDEP_COMPLETIONS -static inline void complete_acquire(struct completion *x) -{ - lock_acquire_exclusive((struct lockdep_map *)&x->map, 0, 0, NULL, _RET_IP_); -} - -static inline void complete_release(struct completion *x) -{ - lock_release((struct lockdep_map *)&x->map, 0, _RET_IP_); -} - -static inline void complete_release_commit(struct completion *x) -{ - lock_commit_crosslock((struct lockdep_map *)&x->map); -} - -#define init_completion_map(x, m) \ -do { \ - lockdep_init_map_crosslock((struct lockdep_map *)&(x)->map, \ - (m)->name, (m)->key, 0); \ - __init_completion(x); \ -} while (0) - -#define init_completion(x) \ -do { \ - static struct lock_class_key __key; \ - lockdep_init_map_crosslock((struct lockdep_map *)&(x)->map, \ - "(completion)" #x, \ - &__key, 0); \ - __init_completion(x); \ -} while (0) -#else #define init_completion_map(x, m) __init_completion(x) #define init_completion(x) __init_completion(x) static inline void complete_acquire(struct completion *x) {} static inline void complete_release(struct completion *x) {} static inline void complete_release_commit(struct completion *x) {} -#endif -#ifdef CONFIG_LOCKDEP_COMPLETIONS -#define COMPLETION_INITIALIZER(work) \ - { 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait), \ - STATIC_CROSS_LOCKDEP_MAP_INIT("(completion)" #work, &(work)) } -#else #define COMPLETION_INITIALIZER(work) \ { 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) } -#endif #define COMPLETION_INITIALIZER_ONSTACK_MAP(work, map) \ (*({ init_completion_map(&(work), &(map)); &(work); })) -- cgit From 527187d28569e39c5d489d6306d3b79605cf85a6 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Mon, 8 Jan 2018 17:27:19 +0100 Subject: locking/lockdep: Remove cross-release leftovers There's two cross-release leftover facilities: - the crossrelease_hist_*() irq-tracing callbacks (NOPs currently) - the complete_release_commit() callback (NOP as well) Remove them. Cc: David Sterba Cc: Byungchul Park Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- include/linux/completion.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/completion.h') diff --git a/include/linux/completion.h b/include/linux/completion.h index 94a59ba7d422..519e94915d18 100644 --- a/include/linux/completion.h +++ b/include/linux/completion.h @@ -32,7 +32,6 @@ struct completion { #define init_completion(x) __init_completion(x) static inline void complete_acquire(struct completion *x) {} static inline void complete_release(struct completion *x) {} -static inline void complete_release_commit(struct completion *x) {} #define COMPLETION_INITIALIZER(work) \ { 0, __WAIT_QUEUE_HEAD_INITIALIZER((work).wait) } -- cgit