From 9a4b99fce659c03699f1cb5003ebe7c57c084d49 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Fri, 26 Feb 2021 09:50:26 -0800 Subject: kernel/futex: Kill rt_mutex_next_owner() Update wake_futex_pi() and kill the call altogether. This is possible because: (i) The case of fixup_owner() in which the pi_mutex was stolen from the signaled enqueued top-waiter which fails to trylock and doesn't see a current owner of the rtmutex but needs to acknowledge an non-enqueued higher priority waiter, which is the other alternative. This used to be handled by rt_mutex_next_owner(), which guaranteed fixup_pi_state_owner('newowner') never to be nil. Nowadays the logic is handled by an EAGAIN loop, without the need of rt_mutex_next_owner(). Specifically: c1e2f0eaf015 (futex: Avoid violating the 10th rule of futex) 9f5d1c336a10 (futex: Handle transient "ownerless" rtmutex state correctly) (ii) rt_mutex_next_owner() and rt_mutex_top_waiter() are semantically equivalent, as of: c28d62cf52d7 (locking/rtmutex: Handle non enqueued waiters gracefully in remove_waiter()) So instead of keeping the call around, just use the good ole rt_mutex_top_waiter(). No change in semantics. Signed-off-by: Davidlohr Bueso Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210226175029.50335-1-dave@stgolabs.net --- kernel/locking/rtmutex_common.h | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index ca6fb489007b..a5007f00c1b7 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -130,7 +130,6 @@ enum rtmutex_chainwalk { /* * PI-futex support (proxy locking functions, etc.): */ -extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock); extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock, struct task_struct *proxy_owner); extern void rt_mutex_proxy_unlock(struct rt_mutex *lock); -- cgit From 2d445c3e4a8216cfa9703998124c13250cc13e5e Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Fri, 26 Mar 2021 16:29:31 +0100 Subject: locking/rtmutex: Remove rtmutex deadlock tester leftovers The following debug members of 'struct rtmutex' are unused: - save_state: No users - file,line: Printed if ::name is NULL. This is only used for non-futex locks so ::name is never NULL - magic: Assigned to NULL by rt_mutex_destroy(), no further usage Remove them along with unused inline and macro leftovers related to the long gone deadlock tester. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210326153943.195064296@linutronix.de --- kernel/locking/rtmutex_common.h | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index a5007f00c1b7..aa047436dadf 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -30,7 +30,6 @@ struct rt_mutex_waiter { struct task_struct *task; struct rt_mutex *lock; #ifdef CONFIG_DEBUG_RT_MUTEXES - unsigned long ip; struct pid *deadlock_task_pid; struct rt_mutex *deadlock_lock; #endif -- cgit From 6d41c675a5394057f6fb1dc97cc0a0e360f2c2f8 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Fri, 26 Mar 2021 16:29:32 +0100 Subject: locking/rtmutex: Remove output from deadlock detector The rtmutex specific deadlock detector predates lockdep coverage of rtmutex and since commit f5694788ad8da ("rt_mutex: Add lockdep annotations") it contains a lot of redundant functionality: - lockdep will detect an potential deadlock before rtmutex-debug has a chance to do so - the deadlock debugging is restricted to rtmutexes which are not associated to futexes and have an active waiter, which is covered by lockdep already Remove the redundant functionality and move actual deadlock WARN() into the deadlock code path. The latter needs a seperate cleanup. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210326153943.320398604@linutronix.de --- kernel/locking/rtmutex_common.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index aa047436dadf..badb2a2803aa 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -29,10 +29,6 @@ struct rt_mutex_waiter { struct rb_node pi_tree_entry; struct task_struct *task; struct rt_mutex *lock; -#ifdef CONFIG_DEBUG_RT_MUTEXES - struct pid *deadlock_task_pid; - struct rt_mutex *deadlock_lock; -#endif int prio; u64 deadline; }; -- cgit From 37350e3b2655eb0fce4e0e6ce8ce631c781136fe Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 26 Mar 2021 16:29:37 +0100 Subject: locking/rtmutex: Remove pointless CONFIG_RT_MUTEXES=n stubs None of these functions are used when CONFIG_RT_MUTEXES=n. Remove the gunk. Remove pointless comments and clean up the coding style mess while at it. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210326153943.863379182@linutronix.de --- kernel/locking/rtmutex_common.h | 62 +++++++++++++---------------------------- 1 file changed, 20 insertions(+), 42 deletions(-) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index badb2a2803aa..8596a71774e0 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -23,29 +23,30 @@ * @tree_entry: pi node to enqueue into the mutex waiters tree * @pi_tree_entry: pi node to enqueue into the mutex owner waiters tree * @task: task reference to the blocked task + * @lock: Pointer to the rt_mutex on which the waiter blocks + * @prio: Priority of the waiter + * @deadline: Deadline of the waiter if applicable */ struct rt_mutex_waiter { - struct rb_node tree_entry; - struct rb_node pi_tree_entry; + struct rb_node tree_entry; + struct rb_node pi_tree_entry; struct task_struct *task; struct rt_mutex *lock; - int prio; - u64 deadline; + int prio; + u64 deadline; }; /* - * Various helpers to access the waiters-tree: + * Must be guarded because this header is included from rcu/tree_plugin.h + * unconditionally. */ - #ifdef CONFIG_RT_MUTEXES - static inline int rt_mutex_has_waiters(struct rt_mutex *lock) { return !RB_EMPTY_ROOT(&lock->waiters.rb_root); } -static inline struct rt_mutex_waiter * -rt_mutex_top_waiter(struct rt_mutex *lock) +static inline struct rt_mutex_waiter *rt_mutex_top_waiter(struct rt_mutex *lock) { struct rb_node *leftmost = rb_first_cached(&lock->waiters); struct rt_mutex_waiter *w = NULL; @@ -62,42 +63,12 @@ static inline int task_has_pi_waiters(struct task_struct *p) return !RB_EMPTY_ROOT(&p->pi_waiters.rb_root); } -static inline struct rt_mutex_waiter * -task_top_pi_waiter(struct task_struct *p) -{ - return rb_entry(p->pi_waiters.rb_leftmost, - struct rt_mutex_waiter, pi_tree_entry); -} - -#else - -static inline int rt_mutex_has_waiters(struct rt_mutex *lock) -{ - return false; -} - -static inline struct rt_mutex_waiter * -rt_mutex_top_waiter(struct rt_mutex *lock) -{ - return NULL; -} - -static inline int task_has_pi_waiters(struct task_struct *p) +static inline struct rt_mutex_waiter *task_top_pi_waiter(struct task_struct *p) { - return false; + return rb_entry(p->pi_waiters.rb_leftmost, struct rt_mutex_waiter, + pi_tree_entry); } -static inline struct rt_mutex_waiter * -task_top_pi_waiter(struct task_struct *p) -{ - return NULL; -} - -#endif - -/* - * lock->owner state tracking: - */ #define RT_MUTEX_HAS_WAITERS 1UL static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) @@ -106,6 +77,13 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) return (struct task_struct *) (owner & ~RT_MUTEX_HAS_WAITERS); } +#else /* CONFIG_RT_MUTEXES */ +/* Used in rcu/tree_plugin.h */ +static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) +{ + return NULL; +} +#endif /* !CONFIG_RT_MUTEXES */ /* * Constants for rt mutex functions which have a selectable deadlock -- cgit From f5a98866e506a816f6a855df1e7ed41e1891ec66 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 26 Mar 2021 16:29:38 +0100 Subject: locking/rtmutex: Decrapify __rt_mutex_init() The conditional debug handling is just another layer of obfuscation. Split the function so rt_mutex_init_proxy_locked() can invoke the inner init and __rt_mutex_init() gets the full treatment. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210326153943.955697588@linutronix.de --- kernel/locking/rtmutex_common.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 8596a71774e0..41adf8be991b 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -100,6 +100,13 @@ enum rtmutex_chainwalk { RT_MUTEX_FULL_CHAINWALK, }; +static inline void __rt_mutex_basic_init(struct rt_mutex *lock) +{ + lock->owner = NULL; + raw_spin_lock_init(&lock->wait_lock); + lock->waiters = RB_ROOT_CACHED; +} + /* * PI-futex support (proxy locking functions, etc.): */ -- cgit From f41dcc18698e660668a33cde8ab965e0298ac341 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 26 Mar 2021 16:29:39 +0100 Subject: locking/rtmutex: Move debug functions as inlines into common header There is no value in having two header files providing just empty stubs and a C file which implements trivial debug functions which can just be inlined. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20210326153944.052454464@linutronix.de --- kernel/locking/rtmutex_common.h | 30 +++++++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) (limited to 'kernel/locking/rtmutex_common.h') diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 41adf8be991b..a90c22abdbca 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -13,6 +13,7 @@ #ifndef __KERNEL_RTMUTEX_COMMON_H #define __KERNEL_RTMUTEX_COMMON_H +#include #include #include @@ -135,10 +136,29 @@ extern bool __rt_mutex_futex_unlock(struct rt_mutex *lock, extern void rt_mutex_postunlock(struct wake_q_head *wake_q); -#ifdef CONFIG_DEBUG_RT_MUTEXES -# include "rtmutex-debug.h" -#else -# include "rtmutex.h" -#endif +/* Debug functions */ +static inline void debug_rt_mutex_unlock(struct rt_mutex *lock) +{ + if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) + DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current); +} + +static inline void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock) +{ + if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) + DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock)); +} + +static inline void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter) +{ + if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) + memset(waiter, 0x11, sizeof(*waiter)); +} + +static inline void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter) +{ + if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES)) + memset(waiter, 0x22, sizeof(*waiter)); +} #endif -- cgit