Add support for Clang's capability analysis for SRCU. Signed-off-by: Marco Elver --- v3: * Switch to DECLARE_LOCK_GUARD_1_ATTRS() (suggested by Peter) * Support SRCU being reentrant. --- .../dev-tools/capability-analysis.rst | 2 +- include/linux/srcu.h | 60 +++++++++++++------ include/linux/srcutiny.h | 4 ++ include/linux/srcutree.h | 6 +- lib/test_capability-analysis.c | 24 ++++++++ 5 files changed, 75 insertions(+), 21 deletions(-) diff --git a/Documentation/dev-tools/capability-analysis.rst b/Documentation/dev-tools/capability-analysis.rst index fdacc7f73da8..779ecb5ec17a 100644 --- a/Documentation/dev-tools/capability-analysis.rst +++ b/Documentation/dev-tools/capability-analysis.rst @@ -82,7 +82,7 @@ Supported Kernel Primitives Currently the following synchronization primitives are supported: `raw_spinlock_t`, `spinlock_t`, `rwlock_t`, `mutex`, `seqlock_t`, -`bit_spinlock`, RCU. +`bit_spinlock`, RCU, SRCU (`srcu_struct`). For capabilities with an initialization function (e.g., `spin_lock_init()`), calling this function on the capability instance before initializing any diff --git a/include/linux/srcu.h b/include/linux/srcu.h index f179700fecaf..6cafaf6dde71 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -21,7 +21,7 @@ #include #include -struct srcu_struct; +struct_with_capability(srcu_struct, __reentrant_cap); #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -53,7 +53,7 @@ int init_srcu_struct(struct srcu_struct *ssp); #define SRCU_READ_FLAVOR_SLOWGP SRCU_READ_FLAVOR_FAST // Flavors requiring synchronize_rcu() // instead of smp_mb(). -void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); +void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases_shared(ssp); #ifdef CONFIG_TINY_SRCU #include @@ -107,14 +107,16 @@ static inline bool same_state_synchronize_srcu(unsigned long oldstate1, unsigned } #ifdef CONFIG_NEED_SRCU_NMI_SAFE -int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); -void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); +int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires_shared(ssp); +void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases_shared(ssp); #else static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) + __acquires_shared(ssp) { return __srcu_read_lock(ssp); } static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) + __releases_shared(ssp) { __srcu_read_unlock(ssp, idx); } @@ -186,6 +188,14 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +/* + * No-op helper to denote that ssp must be held. Because SRCU-protected pointers + * should still be marked with __rcu_guarded, and we do not want to mark them + * with __guarded_by(ssp) as it would complicate annotations for writers, we + * choose the following strategy: srcu_dereference_check() calls this helper + * that checks that the passed ssp is held, and then fake-acquires 'RCU'. + */ +static inline void __srcu_read_lock_must_hold(const struct srcu_struct *ssp) __must_hold_shared(ssp) { } /** * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing @@ -199,9 +209,15 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) * to 1. The @c argument will normally be a logical expression containing * lockdep_is_held() calls. */ -#define srcu_dereference_check(p, ssp, c) \ - __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ - (c) || srcu_read_lock_held(ssp), __rcu) +#define srcu_dereference_check(p, ssp, c) \ +({ \ + __srcu_read_lock_must_hold(ssp); \ + __acquire_shared_cap(RCU); \ + __auto_type __v = __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ + (c) || srcu_read_lock_held(ssp), __rcu); \ + __release_shared_cap(RCU); \ + __v; \ +}) /** * srcu_dereference - fetch SRCU-protected pointer for later dereferencing @@ -244,7 +260,8 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) * invoke srcu_read_unlock() from one task and the matching srcu_read_lock() * from another. */ -static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) +static inline int srcu_read_lock(struct srcu_struct *ssp) + __acquires_shared(ssp) { int retval; @@ -271,7 +288,8 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) * where RCU is watching, that is, from contexts where it would be legal * to invoke rcu_read_lock(). Otherwise, lockdep will complain. */ -static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct *ssp) __acquires(ssp) +static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct *ssp) __acquires_shared(ssp) + __acquires_shared(ssp) { struct srcu_ctr __percpu *retval; @@ -292,7 +310,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct * * The same srcu_struct may be used concurrently by srcu_down_read_fast() * and srcu_read_lock_fast(). */ -static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *ssp) __acquires(ssp) +static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *ssp) __acquires_shared(ssp) { WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); @@ -310,7 +328,8 @@ static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct * * then none of the other flavors may be used, whether before, during, * or after. */ -static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) +static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) + __acquires_shared(ssp) { int retval; @@ -322,7 +341,8 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp /* Used by tracing, cannot be traced and cannot invoke lockdep. */ static inline notrace int -srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) +srcu_read_lock_notrace(struct srcu_struct *ssp) + __acquires_shared(ssp) { int retval; @@ -353,7 +373,8 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) * which calls to down_read() may be nested. The same srcu_struct may be * used concurrently by srcu_down_read() and srcu_read_lock(). */ -static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) +static inline int srcu_down_read(struct srcu_struct *ssp) + __acquires_shared(ssp) { WARN_ON_ONCE(in_nmi()); srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); @@ -368,7 +389,7 @@ static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) * Exit an SRCU read-side critical section. */ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) - __releases(ssp) + __releases_shared(ssp) { WARN_ON_ONCE(idx & ~0x1); srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); @@ -384,7 +405,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) * Exit a light-weight SRCU read-side critical section. */ static inline void srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) - __releases(ssp) + __releases_shared(ssp) { srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); srcu_lock_release(&ssp->dep_map); @@ -400,7 +421,7 @@ static inline void srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ct * the same context as the maching srcu_down_read_fast(). */ static inline void srcu_up_read_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) - __releases(ssp) + __releases_shared(ssp) { WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); @@ -415,7 +436,7 @@ static inline void srcu_up_read_fast(struct srcu_struct *ssp, struct srcu_ctr __ * Exit an SRCU read-side critical section, but in an NMI-safe manner. */ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) - __releases(ssp) + __releases_shared(ssp) { WARN_ON_ONCE(idx & ~0x1); srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); @@ -425,7 +446,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) /* Used by tracing, cannot be traced and cannot call lockdep. */ static inline notrace void -srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) +srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases_shared(ssp) { srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); __srcu_read_unlock(ssp, idx); @@ -440,7 +461,7 @@ srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) * the same context as the maching srcu_down_read(). */ static inline void srcu_up_read(struct srcu_struct *ssp, int idx) - __releases(ssp) + __releases_shared(ssp) { WARN_ON_ONCE(idx & ~0x1); WARN_ON_ONCE(in_nmi()); @@ -480,6 +501,7 @@ DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct, _T->idx = srcu_read_lock(_T->lock), srcu_read_unlock(_T->lock, _T->idx), int idx) +DECLARE_LOCK_GUARD_1_ATTRS(srcu, __assumes_cap(_T), /* */) DEFINE_LOCK_GUARD_1(srcu_fast, struct srcu_struct, _T->scp = srcu_read_lock_fast(_T->lock), diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 51ce25f07930..c194b3c7c43b 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -61,6 +61,7 @@ void synchronize_srcu(struct srcu_struct *ssp); * index that must be passed to the matching srcu_read_unlock(). */ static inline int __srcu_read_lock(struct srcu_struct *ssp) + __acquires_shared(ssp) { int idx; @@ -68,6 +69,7 @@ static inline int __srcu_read_lock(struct srcu_struct *ssp) idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); preempt_enable(); + __acquire_shared(ssp); return idx; } @@ -84,11 +86,13 @@ static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ss } static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp) + __acquires_shared(ssp) { return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp)); } static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) + __releases_shared(ssp) { __srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp)); } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index bf44d8d1e69e..43754472e07a 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -207,7 +207,7 @@ struct srcu_struct { #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) -int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); +int __srcu_read_lock(struct srcu_struct *ssp) __acquires_shared(ssp); void synchronize_srcu_expedited(struct srcu_struct *ssp); void srcu_barrier(struct srcu_struct *ssp); void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); @@ -241,6 +241,7 @@ static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ss * implementations of this_cpu_inc(). */ static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp) + __acquires_shared(ssp) { struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp); @@ -250,6 +251,7 @@ static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct else atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); /* Z */ barrier(); /* Avoid leaking the critical section. */ + __acquire_shared(ssp); return scp; } @@ -269,7 +271,9 @@ static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct * implementations of this_cpu_inc(). */ static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) + __releases_shared(ssp) { + __release_shared(ssp); barrier(); /* Avoid leaking the critical section. */ if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) this_cpu_inc(scp->srcu_unlocks.counter); /* Z */ diff --git a/lib/test_capability-analysis.c b/lib/test_capability-analysis.c index 31c9bc1e2405..5b17fd94f31e 100644 --- a/lib/test_capability-analysis.c +++ b/lib/test_capability-analysis.c @@ -10,6 +10,7 @@ #include #include #include +#include /* * Test that helper macros work as expected. @@ -362,3 +363,26 @@ static void __used test_rcu_assert_variants(void) lockdep_assert_in_rcu_read_lock_sched(); wants_rcu_held_sched(); } + +struct test_srcu_data { + struct srcu_struct srcu; + long __rcu_guarded *data; +}; + +static void __used test_srcu(struct test_srcu_data *d) +{ + init_srcu_struct(&d->srcu); + + int idx = srcu_read_lock(&d->srcu); + long *data = srcu_dereference(d->data, &d->srcu); + (void)data; + srcu_read_unlock(&d->srcu, idx); + + rcu_assign_pointer(d->data, NULL); +} + +static void __used test_srcu_guard(struct test_srcu_data *d) +{ + guard(srcu)(&d->srcu); + (void)srcu_dereference(d->data, &d->srcu); +} -- 2.51.0.384.g4c02a37b29-goog