]> git.ipfire.org Git - thirdparty/kernel/linux.git/commitdiff
locking/local_lock: Support Clang's context analysis
authorMarco Elver <elver@google.com>
Fri, 19 Dec 2025 15:40:08 +0000 (16:40 +0100)
committerPeter Zijlstra <peterz@infradead.org>
Mon, 5 Jan 2026 15:43:31 +0000 (16:43 +0100)
Add support for Clang's context analysis for local_lock_t and
local_trylock_t.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-20-elver@google.com
Documentation/dev-tools/context-analysis.rst
include/linux/local_lock.h
include/linux/local_lock_internal.h
lib/test_context-analysis.c

index 7b660c3003a0b3a67716df80e299370ff9a58a54..a48b75f45e7994ebed189308d19df65b499c3b09 100644 (file)
@@ -80,7 +80,7 @@ Supported Kernel Primitives
 
 Currently the following synchronization primitives are supported:
 `raw_spinlock_t`, `spinlock_t`, `rwlock_t`, `mutex`, `seqlock_t`,
-`bit_spinlock`, RCU, SRCU (`srcu_struct`), `rw_semaphore`.
+`bit_spinlock`, RCU, SRCU (`srcu_struct`), `rw_semaphore`, `local_lock_t`.
 
 For context locks with an initialization function (e.g., `spin_lock_init()`),
 calling this function before initializing any guarded members or globals
index b0e6ab329b0083070457a74c472bb1e899691e63..99c06e49937598f094cfd136fe8d45528d01e385 100644 (file)
  * local_lock - Acquire a per CPU local lock
  * @lock:      The lock variable
  */
-#define local_lock(lock)               __local_lock(this_cpu_ptr(lock))
+#define local_lock(lock)               __local_lock(__this_cpu_local_lock(lock))
 
 /**
  * local_lock_irq - Acquire a per CPU local lock and disable interrupts
  * @lock:      The lock variable
  */
-#define local_lock_irq(lock)           __local_lock_irq(this_cpu_ptr(lock))
+#define local_lock_irq(lock)           __local_lock_irq(__this_cpu_local_lock(lock))
 
 /**
  * local_lock_irqsave - Acquire a per CPU local lock, save and disable
  * @flags:     Storage for interrupt flags
  */
 #define local_lock_irqsave(lock, flags)                                \
-       __local_lock_irqsave(this_cpu_ptr(lock), flags)
+       __local_lock_irqsave(__this_cpu_local_lock(lock), flags)
 
 /**
  * local_unlock - Release a per CPU local lock
  * @lock:      The lock variable
  */
-#define local_unlock(lock)             __local_unlock(this_cpu_ptr(lock))
+#define local_unlock(lock)             __local_unlock(__this_cpu_local_lock(lock))
 
 /**
  * local_unlock_irq - Release a per CPU local lock and enable interrupts
  * @lock:      The lock variable
  */
-#define local_unlock_irq(lock)         __local_unlock_irq(this_cpu_ptr(lock))
+#define local_unlock_irq(lock)         __local_unlock_irq(__this_cpu_local_lock(lock))
 
 /**
  * local_unlock_irqrestore - Release a per CPU local lock and restore
@@ -50,7 +50,7 @@
  * @flags:      Interrupt flags to restore
  */
 #define local_unlock_irqrestore(lock, flags)                   \
-       __local_unlock_irqrestore(this_cpu_ptr(lock), flags)
+       __local_unlock_irqrestore(__this_cpu_local_lock(lock), flags)
 
 /**
  * local_trylock_init - Runtime initialize a lock instance
@@ -66,7 +66,7 @@
  * locking constrains it will _always_ fail to acquire the lock in NMI or
  * HARDIRQ context on PREEMPT_RT.
  */
-#define local_trylock(lock)            __local_trylock(this_cpu_ptr(lock))
+#define local_trylock(lock)            __local_trylock(__this_cpu_local_lock(lock))
 
 #define local_lock_is_locked(lock)     __local_lock_is_locked(lock)
 
  * HARDIRQ context on PREEMPT_RT.
  */
 #define local_trylock_irqsave(lock, flags)                     \
-       __local_trylock_irqsave(this_cpu_ptr(lock), flags)
-
-DEFINE_GUARD(local_lock, local_lock_t __percpu*,
-            local_lock(_T),
-            local_unlock(_T))
-DEFINE_GUARD(local_lock_irq, local_lock_t __percpu*,
-            local_lock_irq(_T),
-            local_unlock_irq(_T))
+       __local_trylock_irqsave(__this_cpu_local_lock(lock), flags)
+
+DEFINE_LOCK_GUARD_1(local_lock, local_lock_t __percpu,
+                   local_lock(_T->lock),
+                   local_unlock(_T->lock))
+DEFINE_LOCK_GUARD_1(local_lock_irq, local_lock_t __percpu,
+                   local_lock_irq(_T->lock),
+                   local_unlock_irq(_T->lock))
 DEFINE_LOCK_GUARD_1(local_lock_irqsave, local_lock_t __percpu,
                    local_lock_irqsave(_T->lock, _T->flags),
                    local_unlock_irqrestore(_T->lock, _T->flags),
                    unsigned long flags)
 
 #define local_lock_nested_bh(_lock)                            \
-       __local_lock_nested_bh(this_cpu_ptr(_lock))
+       __local_lock_nested_bh(__this_cpu_local_lock(_lock))
 
 #define local_unlock_nested_bh(_lock)                          \
-       __local_unlock_nested_bh(this_cpu_ptr(_lock))
-
-DEFINE_GUARD(local_lock_nested_bh, local_lock_t __percpu*,
-            local_lock_nested_bh(_T),
-            local_unlock_nested_bh(_T))
+       __local_unlock_nested_bh(__this_cpu_local_lock(_lock))
+
+DEFINE_LOCK_GUARD_1(local_lock_nested_bh, local_lock_t __percpu,
+                   local_lock_nested_bh(_T->lock),
+                   local_unlock_nested_bh(_T->lock))
+
+DECLARE_LOCK_GUARD_1_ATTRS(local_lock, __acquires(_T), __releases(*(local_lock_t __percpu **)_T))
+#define class_local_lock_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock, _T)
+DECLARE_LOCK_GUARD_1_ATTRS(local_lock_irq, __acquires(_T), __releases(*(local_lock_t __percpu **)_T))
+#define class_local_lock_irq_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_irq, _T)
+DECLARE_LOCK_GUARD_1_ATTRS(local_lock_irqsave, __acquires(_T), __releases(*(local_lock_t __percpu **)_T))
+#define class_local_lock_irqsave_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_irqsave, _T)
+DECLARE_LOCK_GUARD_1_ATTRS(local_lock_nested_bh, __acquires(_T), __releases(*(local_lock_t __percpu **)_T))
+#define class_local_lock_nested_bh_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(local_lock_nested_bh, _T)
 
 #endif
index 1a1ea1232addbdd675b46a9da32d664e19e30967..e8c4803d8db48b2074169e9b654fa80d3eeb837d 100644 (file)
 
 #ifndef CONFIG_PREEMPT_RT
 
-typedef struct {
+context_lock_struct(local_lock) {
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
        struct lockdep_map      dep_map;
        struct task_struct      *owner;
 #endif
-} local_lock_t;
+};
+typedef struct local_lock local_lock_t;
 
 /* local_trylock() and local_trylock_irqsave() only work with local_trylock_t */
-typedef struct {
+context_lock_struct(local_trylock) {
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
        struct lockdep_map      dep_map;
        struct task_struct      *owner;
 #endif
        u8              acquired;
-} local_trylock_t;
+};
+typedef struct local_trylock local_trylock_t;
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define LOCAL_LOCK_DEBUG_INIT(lockname)               \
@@ -84,9 +86,14 @@ do {                                                         \
                              0, LD_WAIT_CONFIG, LD_WAIT_INV,   \
                              LD_LOCK_PERCPU);                  \
        local_lock_debug_init(lock);                            \
+       __assume_ctx_lock(lock);                                \
 } while (0)
 
-#define __local_trylock_init(lock) __local_lock_init((local_lock_t *)lock)
+#define __local_trylock_init(lock)                             \
+do {                                                           \
+       __local_lock_init((local_lock_t *)lock);                \
+       __assume_ctx_lock(lock);                                \
+} while (0)
 
 #define __spinlock_nested_bh_init(lock)                                \
 do {                                                           \
@@ -97,6 +104,7 @@ do {                                                         \
                              0, LD_WAIT_CONFIG, LD_WAIT_INV,   \
                              LD_LOCK_NORMAL);                  \
        local_lock_debug_init(lock);                            \
+       __assume_ctx_lock(lock);                                \
 } while (0)
 
 #define __local_lock_acquire(lock)                                     \
@@ -119,22 +127,25 @@ do {                                                              \
        do {                                                    \
                preempt_disable();                              \
                __local_lock_acquire(lock);                     \
+               __acquire(lock);                                \
        } while (0)
 
 #define __local_lock_irq(lock)                                 \
        do {                                                    \
                local_irq_disable();                            \
                __local_lock_acquire(lock);                     \
+               __acquire(lock);                                \
        } while (0)
 
 #define __local_lock_irqsave(lock, flags)                      \
        do {                                                    \
                local_irq_save(flags);                          \
                __local_lock_acquire(lock);                     \
+               __acquire(lock);                                \
        } while (0)
 
 #define __local_trylock(lock)                                  \
-       ({                                                      \
+       __try_acquire_ctx_lock(lock, ({                         \
                local_trylock_t *__tl;                          \
                                                                \
                preempt_disable();                              \
@@ -148,10 +159,10 @@ do {                                                              \
                                (local_lock_t *)__tl);          \
                }                                               \
                !!__tl;                                         \
-       })
+       }))
 
 #define __local_trylock_irqsave(lock, flags)                   \
-       ({                                                      \
+       __try_acquire_ctx_lock(lock, ({                         \
                local_trylock_t *__tl;                          \
                                                                \
                local_irq_save(flags);                          \
@@ -165,7 +176,7 @@ do {                                                                \
                                (local_lock_t *)__tl);          \
                }                                               \
                !!__tl;                                         \
-       })
+       }))
 
 /* preemption or migration must be disabled before calling __local_lock_is_locked */
 #define __local_lock_is_locked(lock) READ_ONCE(this_cpu_ptr(lock)->acquired)
@@ -188,18 +199,21 @@ do {                                                              \
 
 #define __local_unlock(lock)                                   \
        do {                                                    \
+               __release(lock);                                \
                __local_lock_release(lock);                     \
                preempt_enable();                               \
        } while (0)
 
 #define __local_unlock_irq(lock)                               \
        do {                                                    \
+               __release(lock);                                \
                __local_lock_release(lock);                     \
                local_irq_enable();                             \
        } while (0)
 
 #define __local_unlock_irqrestore(lock, flags)                 \
        do {                                                    \
+               __release(lock);                                \
                __local_lock_release(lock);                     \
                local_irq_restore(flags);                       \
        } while (0)
@@ -208,13 +222,19 @@ do {                                                              \
        do {                                                    \
                lockdep_assert_in_softirq();                    \
                local_lock_acquire((lock));                     \
+               __acquire(lock);                                \
        } while (0)
 
 #define __local_unlock_nested_bh(lock)                         \
-       local_lock_release((lock))
+       do {                                                    \
+               __release(lock);                                \
+               local_lock_release((lock));                     \
+       } while (0)
 
 #else /* !CONFIG_PREEMPT_RT */
 
+#include <linux/spinlock.h>
+
 /*
  * On PREEMPT_RT local_lock maps to a per CPU spinlock, which protects the
  * critical section while staying preemptible.
@@ -269,7 +289,7 @@ do {                                                                \
 } while (0)
 
 #define __local_trylock(lock)                                  \
-       ({                                                      \
+       __try_acquire_ctx_lock(lock, context_unsafe(({          \
                int __locked;                                   \
                                                                \
                if (in_nmi() | in_hardirq()) {                  \
@@ -281,17 +301,40 @@ do {                                                              \
                                migrate_enable();               \
                }                                               \
                __locked;                                       \
-       })
+       })))
 
 #define __local_trylock_irqsave(lock, flags)                   \
-       ({                                                      \
+       __try_acquire_ctx_lock(lock, ({                         \
                typecheck(unsigned long, flags);                \
                flags = 0;                                      \
                __local_trylock(lock);                          \
-       })
+       }))
 
 /* migration must be disabled before calling __local_lock_is_locked */
 #define __local_lock_is_locked(__lock)                                 \
        (rt_mutex_owner(&this_cpu_ptr(__lock)->lock) == current)
 
 #endif /* CONFIG_PREEMPT_RT */
+
+#if defined(WARN_CONTEXT_ANALYSIS)
+/*
+ * Because the compiler only knows about the base per-CPU variable, use this
+ * helper function to make the compiler think we lock/unlock the @base variable,
+ * and hide the fact we actually pass the per-CPU instance to lock/unlock
+ * functions.
+ */
+static __always_inline local_lock_t *__this_cpu_local_lock(local_lock_t __percpu *base)
+       __returns_ctx_lock(base) __attribute__((overloadable))
+{
+       return this_cpu_ptr(base);
+}
+#ifndef CONFIG_PREEMPT_RT
+static __always_inline local_trylock_t *__this_cpu_local_lock(local_trylock_t __percpu *base)
+       __returns_ctx_lock(base) __attribute__((overloadable))
+{
+       return this_cpu_ptr(base);
+}
+#endif /* CONFIG_PREEMPT_RT */
+#else  /* WARN_CONTEXT_ANALYSIS */
+#define __this_cpu_local_lock(base) this_cpu_ptr(base)
+#endif /* WARN_CONTEXT_ANALYSIS */
index 1c96c56cf87369730068f328122389e5443dc4c1..003e64cac540a8fe264989d5b381c14657634abe 100644 (file)
@@ -6,7 +6,9 @@
 
 #include <linux/bit_spinlock.h>
 #include <linux/build_bug.h>
+#include <linux/local_lock.h>
 #include <linux/mutex.h>
+#include <linux/percpu.h>
 #include <linux/rcupdate.h>
 #include <linux/rwsem.h>
 #include <linux/seqlock.h>
@@ -458,3 +460,74 @@ static void __used test_srcu_guard(struct test_srcu_data *d)
        { guard(srcu_fast)(&d->srcu); (void)srcu_dereference(d->data, &d->srcu); }
        { guard(srcu_fast_notrace)(&d->srcu); (void)srcu_dereference(d->data, &d->srcu); }
 }
+
+struct test_local_lock_data {
+       local_lock_t lock;
+       int counter __guarded_by(&lock);
+};
+
+static DEFINE_PER_CPU(struct test_local_lock_data, test_local_lock_data) = {
+       .lock = INIT_LOCAL_LOCK(lock),
+};
+
+static void __used test_local_lock_init(struct test_local_lock_data *d)
+{
+       local_lock_init(&d->lock);
+       d->counter = 0;
+}
+
+static void __used test_local_lock(void)
+{
+       unsigned long flags;
+
+       local_lock(&test_local_lock_data.lock);
+       this_cpu_add(test_local_lock_data.counter, 1);
+       local_unlock(&test_local_lock_data.lock);
+
+       local_lock_irq(&test_local_lock_data.lock);
+       this_cpu_add(test_local_lock_data.counter, 1);
+       local_unlock_irq(&test_local_lock_data.lock);
+
+       local_lock_irqsave(&test_local_lock_data.lock, flags);
+       this_cpu_add(test_local_lock_data.counter, 1);
+       local_unlock_irqrestore(&test_local_lock_data.lock, flags);
+
+       local_lock_nested_bh(&test_local_lock_data.lock);
+       this_cpu_add(test_local_lock_data.counter, 1);
+       local_unlock_nested_bh(&test_local_lock_data.lock);
+}
+
+static void __used test_local_lock_guard(void)
+{
+       { guard(local_lock)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
+       { guard(local_lock_irq)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
+       { guard(local_lock_irqsave)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
+       { guard(local_lock_nested_bh)(&test_local_lock_data.lock); this_cpu_add(test_local_lock_data.counter, 1); }
+}
+
+struct test_local_trylock_data {
+       local_trylock_t lock;
+       int counter __guarded_by(&lock);
+};
+
+static DEFINE_PER_CPU(struct test_local_trylock_data, test_local_trylock_data) = {
+       .lock = INIT_LOCAL_TRYLOCK(lock),
+};
+
+static void __used test_local_trylock_init(struct test_local_trylock_data *d)
+{
+       local_trylock_init(&d->lock);
+       d->counter = 0;
+}
+
+static void __used test_local_trylock(void)
+{
+       local_lock(&test_local_trylock_data.lock);
+       this_cpu_add(test_local_trylock_data.counter, 1);
+       local_unlock(&test_local_trylock_data.lock);
+
+       if (local_trylock(&test_local_trylock_data.lock)) {
+               this_cpu_add(test_local_trylock_data.counter, 1);
+               local_unlock(&test_local_trylock_data.lock);
+       }
+}