From fc7a7e2064b153bb5033a68872f5744029540b41 Mon Sep 17 00:00:00 2001 From: Todd Kjos Date: Mon, 29 May 2017 16:44:24 -0700 Subject: [PATCH] FROMLIST: binder: introduce locking helper functions (from https://patchwork.kernel.org/patch/9817791/) There are 3 main spinlocks which must be acquired in this order: 1) proc->outer_lock : protects most fields of binder_proc, binder_thread, and binder_ref structures. binder_proc_lock() and binder_proc_unlock() are used to acq/rel. 2) node->lock : protects most fields of binder_node. binder_node_lock() and binder_node_unlock() are used to acq/rel 3) proc->inner_lock : protects the thread and node lists (proc->threads, proc->nodes) and all todo lists associated with the binder_proc (proc->todo, thread->todo, proc->delivered_death and node->async_todo). binder_inner_proc_lock() and binder_inner_proc_unlock() are used to acq/rel Any lock under procA must never be nested under any lock at the same level or below on procB. Functions that require a lock held on entry indicate which lock in the suffix of the function name: foo_olocked() : requires node->outer_lock foo_nlocked() : requires node->lock foo_ilocked() : requires proc->inner_lock foo_iolocked(): requires proc->outer_lock and proc->inner_lock foo_nilocked(): requires node->lock and proc->inner_lock Change-Id: Ic11bf3bf988e0a901ce0484e2fd9323b176994c3 Signed-off-by: Todd Kjos --- drivers/android/binder.c | 238 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 238 insertions(+) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 9db9f4acad9a..448442f375e0 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -15,6 +15,39 @@ * */ +/* + * Locking overview + * + * There are 3 main spinlocks which must be acquired in the + * order shown: + * + * 1) proc->outer_lock : protects binder_ref + * binder_proc_lock() and binder_proc_unlock() are + * used to acq/rel. + * 2) node->lock : protects most fields of binder_node. + * binder_node_lock() and binder_node_unlock() are + * used to acq/rel + * 3) proc->inner_lock : protects the thread and node lists + * (proc->threads, proc->nodes) and all todo lists associated + * with the binder_proc (proc->todo, thread->todo, + * proc->delivered_death and node->async_todo). + * binder_inner_proc_lock() and binder_inner_proc_unlock() + * are used to acq/rel + * + * Any lock under procA must never be nested under any lock at the same + * level or below on procB. + * + * Functions that require a lock held on entry indicate which lock + * in the suffix of the function name: + * + * foo_olocked() : requires node->outer_lock + * foo_nlocked() : requires node->lock + * foo_ilocked() : requires proc->inner_lock + * foo_oilocked(): requires proc->outer_lock and proc->inner_lock + * foo_nilocked(): requires node->lock and proc->inner_lock + * ... + */ + #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include @@ -35,6 +68,7 @@ #include #include #include +#include #ifdef CONFIG_ANDROID_BINDER_IPC_32BIT #define BINDER_IPC_32BIT 1 @@ -105,6 +139,7 @@ enum { BINDER_DEBUG_FREE_BUFFER = 1U << 11, BINDER_DEBUG_INTERNAL_REFS = 1U << 12, BINDER_DEBUG_PRIORITY_CAP = 1U << 13, + BINDER_DEBUG_SPINLOCKS = 1U << 14, }; static uint32_t binder_debug_mask = BINDER_DEBUG_USER_ERROR | BINDER_DEBUG_FAILED_TRANSACTION | BINDER_DEBUG_DEAD_TRANSACTION; @@ -261,8 +296,43 @@ struct binder_error { uint32_t cmd; }; +/** + * struct binder_node - binder node bookkeeping + * @debug_id: unique ID for debugging + * (invariant after initialized) + * @lock: lock for node fields + * @work: worklist element for node work + * @rb_node: element for proc->nodes tree + * @dead_node: element for binder_dead_nodes list + * (protected by binder_dead_nodes_lock) + * @proc: binder_proc that owns this node + * (invariant after initialized) + * @refs: list of references on this node + * @internal_strong_refs: used to take strong references when + * initiating a transaction + * @local_weak_refs: weak user refs from local process + * @local_strong_refs: strong user refs from local process + * @tmp_refs: temporary kernel refs + * @ptr: userspace pointer for node + * (invariant, no lock needed) + * @cookie: userspace cookie for node + * (invariant, no lock needed) + * @has_strong_ref: userspace notified of strong ref + * @pending_strong_ref: userspace has acked notification of strong ref + * @has_weak_ref: userspace notified of weak ref + * @pending_weak_ref: userspace has acked notification of weak ref + * @has_async_transaction: async transaction to node in progress + * @accept_fds: file descriptor operations supported for node + * (invariant after initialized) + * @min_priority: minimum scheduling priority + * (invariant after initialized) + * @async_todo: list of async work items + * + * Bookkeeping structure for binder nodes. + */ struct binder_node { int debug_id; + spinlock_t lock; struct binder_work work; union { struct rb_node rb_node; @@ -345,6 +415,51 @@ enum binder_deferred_state { BINDER_DEFERRED_RELEASE = 0x04, }; +/** + * struct binder_proc - binder process bookkeeping + * @proc_node: element for binder_procs list + * @threads: rbtree of binder_threads in this proc + * @nodes: rbtree of binder nodes associated with + * this proc ordered by node->ptr + * @refs_by_desc: rbtree of refs ordered by ref->desc + * @refs_by_node: rbtree of refs ordered by ref->node + * @pid PID of group_leader of process + * (invariant after initialized) + * @tsk task_struct for group_leader of process + * (invariant after initialized) + * @files files_struct for process + * (invariant after initialized) + * @deferred_work_node: element for binder_deferred_list + * (protected by binder_deferred_lock) + * @deferred_work: bitmap of deferred work to perform + * (protected by binder_deferred_lock) + * @is_dead: process is dead and awaiting free + * when outstanding transactions are cleaned up + * @todo: list of work for this process + * @wait: wait queue head to wait for proc work + * (invariant after initialized) + * @stats: per-process binder statistics + * (atomics, no lock needed) + * @delivered_death: list of delivered death notification + * @max_threads: cap on number of binder threads + * @requested_threads: number of binder threads requested but not + * yet started. In current implementation, can + * only be 0 or 1. + * @requested_threads_started: number binder threads started + * @ready_threads: number of threads waiting for proc work + * @tmp_ref: temporary reference to indicate proc is in use + * @default_priority: default scheduler priority + * (invariant after initialized) + * @debugfs_entry: debugfs node + * @alloc: binder allocator bookkeeping + * @context: binder_context for this proc + * (invariant after initialized) + * @inner_lock: can nest under outer_lock and/or node lock + * @outer_lock: no nesting under innor or node lock + * Lock order: 1) outer, 2) node, 3) inner + * + * Bookkeeping structure for binder processes + */ struct binder_proc { struct hlist_node proc_node; struct rb_root threads; @@ -371,6 +486,8 @@ struct binder_proc { struct dentry *debugfs_entry; struct binder_alloc alloc; struct binder_context *context; + spinlock_t inner_lock; + spinlock_t outer_lock; }; enum { @@ -381,6 +498,33 @@ enum { BINDER_LOOPER_STATE_WAITING = 0x10, }; +/** + * struct binder_thread - binder thread bookkeeping + * @proc: binder process for this thread + * (invariant after initialization) + * @rb_node: element for proc->threads rbtree + * @pid: PID for this thread + * (invariant after initialization) + * @looper: bitmap of looping state + * (only accessed by this thread) + * @looper_needs_return: looping thread needs to exit driver + * (no lock needed) + * @transaction_stack: stack of in-progress transactions for this thread + * @todo: list of work to do for this thread + * @return_error: transaction errors reported by this thread + * (only accessed by this thread) + * @reply_error: transaction errors reported by target thread + * @wait: wait queue for thread work + * @stats: per-thread statistics + * (atomics, no lock needed) + * @tmp_ref: temporary reference to indicate thread is in use + * (atomic since @proc->inner_lock cannot + * always be acquired) + * @is_dead: thread is dead and awaiting free + * when outstanding transactions are cleaned up + * + * Bookkeeping structure for binder threads. + */ struct binder_thread { struct binder_proc *proc; struct rb_node rb_node; @@ -423,6 +567,97 @@ struct binder_transaction { spinlock_t lock; }; +/** + * binder_proc_lock() - Acquire outer lock for given binder_proc + * @proc: struct binder_proc to acquire + * + * Acquires proc->outer_lock. Used to protect binder_ref + * structures associated with the given proc. + */ +#define binder_proc_lock(proc) _binder_proc_lock(proc, __LINE__) +static void +_binder_proc_lock(struct binder_proc *proc, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_lock(&proc->outer_lock); +} + +/** + * binder_proc_unlock() - Release spinlock for given binder_proc + * @proc: struct binder_proc to acquire + * + * Release lock acquired via binder_proc_lock() + */ +#define binder_proc_unlock(_proc) _binder_proc_unlock(_proc, __LINE__) +static void +_binder_proc_unlock(struct binder_proc *proc, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_unlock(&proc->outer_lock); +} + +/** + * binder_inner_proc_lock() - Acquire inner lock for given binder_proc + * @proc: struct binder_proc to acquire + * + * Acquires proc->inner_lock. Used to protect todo lists + */ +#define binder_inner_proc_lock(proc) _binder_inner_proc_lock(proc, __LINE__) +static void +_binder_inner_proc_lock(struct binder_proc *proc, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_lock(&proc->inner_lock); +} + +/** + * binder_inner_proc_unlock() - Release inner lock for given binder_proc + * @proc: struct binder_proc to acquire + * + * Release lock acquired via binder_inner_proc_lock() + */ +#define binder_inner_proc_unlock(proc) _binder_inner_proc_unlock(proc, __LINE__) +static void +_binder_inner_proc_unlock(struct binder_proc *proc, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_unlock(&proc->inner_lock); +} + +/** + * binder_node_lock() - Acquire spinlock for given binder_node + * @node: struct binder_node to acquire + * + * Acquires node->lock. Used to protect binder_node fields + */ +#define binder_node_lock(node) _binder_node_lock(node, __LINE__) +static void +_binder_node_lock(struct binder_node *node, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_lock(&node->lock); +} + +/** + * binder_node_unlock() - Release spinlock for given binder_proc + * @node: struct binder_node to acquire + * + * Release lock acquired via binder_node_lock() + */ +#define binder_node_unlock(node) _binder_node_unlock(node, __LINE__) +static void +_binder_node_unlock(struct binder_node *node, int line) +{ + binder_debug(BINDER_DEBUG_SPINLOCKS, + "%s: line=%d\n", __func__, line); + spin_unlock(&node->lock); +} + static void binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer); static void binder_free_thread(struct binder_thread *thread); @@ -567,6 +802,7 @@ static struct binder_node *binder_new_node(struct binder_proc *proc, node->ptr = ptr; node->cookie = cookie; node->work.type = BINDER_WORK_NODE; + spin_lock_init(&node->lock); INIT_LIST_HEAD(&node->work.entry); INIT_LIST_HEAD(&node->async_todo); binder_debug(BINDER_DEBUG_INTERNAL_REFS, @@ -3599,6 +3835,8 @@ static int binder_open(struct inode *nodp, struct file *filp) proc = kzalloc(sizeof(*proc), GFP_KERNEL); if (proc == NULL) return -ENOMEM; + spin_lock_init(&proc->inner_lock); + spin_lock_init(&proc->outer_lock); get_task_struct(current->group_leader); proc->tsk = current->group_leader; INIT_LIST_HEAD(&proc->todo); -- 2.20.1