From 3771b0fe9dfc3801eac0142d1af6ba94dee83c6c Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 25 Mar 2019 13:57:57 +0100 Subject: locking/lockdep: Avoid bogus Clang warning When lockdep is enabled, and -Wuninitialized warnings are enabled, Clang produces a silly warning for every file we compile: In file included from kernel/sched/fair.c:23: kernel/sched/sched.h:1094:15: error: variable 'cookie' is uninitialized when used here [-Werror,-Wuninitialized] rf->cookie = lockdep_pin_lock(&rq->lock); ^~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/lockdep.h:474:60: note: expanded from macro 'lockdep_pin_lock' #define lockdep_pin_lock(l) ({ struct pin_cookie cookie; cookie; }) ^~~~~~ kernel/sched/sched.h:1094:15: note: variable 'cookie' is declared here include/linux/lockdep.h:474:34: note: expanded from macro 'lockdep_pin_lock' #define lockdep_pin_lock(l) ({ struct pin_cookie cookie; cookie; }) ^ As the 'struct pin_cookie' structure is empty in this configuration, there is no need to initialize it for correctness, but it also does not hurt to set it to an empty structure, so do that to avoid the warning. Signed-off-by: Arnd Bergmann Acked-by: Will Deacon Cc: Bart Van Assche Cc: Joel Fernandes (Google) Cc: Linus Torvalds Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Steven Rostedt (VMware) Cc: Thomas Gleixner Cc: Waiman Long Cc: clang-built-linux@googlegroups.com Link: http://lkml.kernel.org/r/20190325125807.1437049-1-arnd@arndb.de Signed-off-by: Ingo Molnar --- include/linux/lockdep.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/lockdep.h') diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 79c3873d58ac..21725a91442b 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -471,7 +471,7 @@ struct pin_cookie { }; #define NIL_COOKIE (struct pin_cookie){ } -#define lockdep_pin_lock(l) ({ struct pin_cookie cookie; cookie; }) +#define lockdep_pin_lock(l) ({ struct pin_cookie cookie = { }; cookie; }) #define lockdep_repin_lock(l, c) do { (void)(l); (void)(c); } while (0) #define lockdep_unpin_lock(l, c) do { (void)(l); (void)(c); } while (0) -- cgit v1.2.3 From c120bce78065cbea460a58b1572c215db9c148ba Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 25 Apr 2019 11:45:12 +0200 Subject: lockdep: Simplify stack trace handling Replace the indirection through struct stack_trace by using the storage array based interfaces and storing the information is a small lockdep specific data structure. Signed-off-by: Thomas Gleixner Reviewed-by: Josh Poimboeuf Acked-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Steven Rostedt Cc: Alexander Potapenko Cc: Alexey Dobriyan Cc: Andrew Morton Cc: Christoph Lameter Cc: Pekka Enberg Cc: linux-mm@kvack.org Cc: David Rientjes Cc: Catalin Marinas Cc: Dmitry Vyukov Cc: Andrey Ryabinin Cc: kasan-dev@googlegroups.com Cc: Mike Rapoport Cc: Akinobu Mita Cc: Christoph Hellwig Cc: iommu@lists.linux-foundation.org Cc: Robin Murphy Cc: Marek Szyprowski Cc: Johannes Thumshirn Cc: David Sterba Cc: Chris Mason Cc: Josef Bacik Cc: linux-btrfs@vger.kernel.org Cc: dm-devel@redhat.com Cc: Mike Snitzer Cc: Alasdair Kergon Cc: Daniel Vetter Cc: intel-gfx@lists.freedesktop.org Cc: Joonas Lahtinen Cc: Maarten Lankhorst Cc: dri-devel@lists.freedesktop.org Cc: David Airlie Cc: Jani Nikula Cc: Rodrigo Vivi Cc: Tom Zanussi Cc: Miroslav Benes Cc: linux-arch@vger.kernel.org Link: https://lkml.kernel.org/r/20190425094802.891724020@linutronix.de --- include/linux/lockdep.h | 9 ++++++-- kernel/locking/lockdep.c | 55 ++++++++++++++++++++++++------------------------ 2 files changed, 35 insertions(+), 29 deletions(-) (limited to 'include/linux/lockdep.h') diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 79c3873d58ac..6f165d625320 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -66,6 +66,11 @@ struct lock_class_key { extern struct lock_class_key __lockdep_no_validate__; +struct lock_trace { + unsigned int nr_entries; + unsigned int offset; +}; + #define LOCKSTAT_POINTS 4 /* @@ -100,7 +105,7 @@ struct lock_class { * IRQ/softirq usage tracking bits: */ unsigned long usage_mask; - struct stack_trace usage_traces[XXX_LOCK_USAGE_STATES]; + struct lock_trace usage_traces[XXX_LOCK_USAGE_STATES]; /* * Generation counter, when doing certain classes of graph walking, @@ -188,7 +193,7 @@ struct lock_list { struct list_head entry; struct lock_class *class; struct lock_class *links_to; - struct stack_trace trace; + struct lock_trace trace; int distance; /* diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 3603893d5bbd..45bcaf2e4cb6 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -434,18 +434,14 @@ static void print_lockdep_off(const char *bug_msg) #endif } -static int save_trace(struct stack_trace *trace) +static int save_trace(struct lock_trace *trace) { - trace->nr_entries = 0; - trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries; - trace->entries = stack_trace + nr_stack_trace_entries; - - trace->skip = 3; - - save_stack_trace(trace); - - trace->max_entries = trace->nr_entries; + unsigned long *entries = stack_trace + nr_stack_trace_entries; + unsigned int max_entries; + trace->offset = nr_stack_trace_entries; + max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries; + trace->nr_entries = stack_trace_save(entries, max_entries, 3); nr_stack_trace_entries += trace->nr_entries; if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) { @@ -1196,7 +1192,7 @@ static struct lock_list *alloc_list_entry(void) static int add_lock_to_list(struct lock_class *this, struct lock_class *links_to, struct list_head *head, unsigned long ip, int distance, - struct stack_trace *trace) + struct lock_trace *trace) { struct lock_list *entry; /* @@ -1415,6 +1411,13 @@ static inline int __bfs_backwards(struct lock_list *src_entry, * checking. */ +static void print_lock_trace(struct lock_trace *trace, unsigned int spaces) +{ + unsigned long *entries = stack_trace + trace->offset; + + stack_trace_print(entries, trace->nr_entries, spaces); +} + /* * Print a dependency chain entry (this is only done when a deadlock * has been detected): @@ -1427,8 +1430,7 @@ print_circular_bug_entry(struct lock_list *target, int depth) printk("\n-> #%u", depth); print_lock_name(target->class); printk(KERN_CONT ":\n"); - print_stack_trace(&target->trace, 6); - + print_lock_trace(&target->trace, 6); return 0; } @@ -1740,7 +1742,7 @@ static void print_lock_class_header(struct lock_class *class, int depth) len += printk("%*s %s", depth, "", usage_str[bit]); len += printk(KERN_CONT " at:\n"); - print_stack_trace(class->usage_traces + bit, len); + print_lock_trace(class->usage_traces + bit, len); } } printk("%*s }\n", depth, ""); @@ -1765,7 +1767,7 @@ print_shortest_lock_dependencies(struct lock_list *leaf, do { print_lock_class_header(entry->class, depth); printk("%*s ... acquired at:\n", depth, ""); - print_stack_trace(&entry->trace, 2); + print_lock_trace(&entry->trace, 2); printk("\n"); if (depth == 0 && (entry != root)) { @@ -1878,14 +1880,14 @@ print_bad_irq_dependency(struct task_struct *curr, print_lock_name(backwards_entry->class); pr_warn("\n... which became %s-irq-safe at:\n", irqclass); - print_stack_trace(backwards_entry->class->usage_traces + bit1, 1); + print_lock_trace(backwards_entry->class->usage_traces + bit1, 1); pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass); print_lock_name(forwards_entry->class); pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass); pr_warn("..."); - print_stack_trace(forwards_entry->class->usage_traces + bit2, 1); + print_lock_trace(forwards_entry->class->usage_traces + bit2, 1); pr_warn("\nother info that might help us debug this:\n\n"); print_irq_lock_scenario(backwards_entry, forwards_entry, @@ -2158,7 +2160,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next, */ static int check_prev_add(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, int distance, struct stack_trace *trace) + struct held_lock *next, int distance, struct lock_trace *trace) { struct lock_list *uninitialized_var(target_entry); struct lock_list *entry; @@ -2196,7 +2198,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, this.parent = NULL; ret = check_noncircular(&this, hlock_class(prev), &target_entry); if (unlikely(!ret)) { - if (!trace->entries) { + if (!trace->nr_entries) { /* * If save_trace fails here, the printing might * trigger a WARN but because of the !nr_entries it @@ -2252,7 +2254,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, return print_bfs_bug(ret); - if (!trace->entries && !save_trace(trace)) + if (!trace->nr_entries && !save_trace(trace)) return 0; /* @@ -2284,14 +2286,9 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev, static int check_prevs_add(struct task_struct *curr, struct held_lock *next) { + struct lock_trace trace = { .nr_entries = 0 }; int depth = curr->lockdep_depth; struct held_lock *hlock; - struct stack_trace trace = { - .nr_entries = 0, - .max_entries = 0, - .entries = NULL, - .skip = 0, - }; /* * Debugging checks. @@ -2719,6 +2716,10 @@ static inline int validate_chain(struct task_struct *curr, { return 1; } + +static void print_lock_trace(struct lock_trace *trace, unsigned int spaces) +{ +} #endif /* @@ -2815,7 +2816,7 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this, print_lock(this); pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]); - print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1); + print_lock_trace(hlock_class(this)->usage_traces + prev_bit, 1); print_irqtrace_events(curr); pr_warn("\nother info that might help us debug this:\n"); -- cgit v1.2.3