diff options
| -rw-r--r-- | arch/Kconfig | 3 | ||||
| -rw-r--r-- | include/linux/srcu.h | 51 | ||||
| -rw-r--r-- | kernel/rcu/Kconfig | 3 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 11 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 43 |
5 files changed, 105 insertions, 6 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 8f138e580d1a..6b95244c3057 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -468,6 +468,9 @@ config ARCH_WANT_IRQS_OFF_ACTIVATE_MM config ARCH_HAVE_NMI_SAFE_CMPXCHG bool +config ARCH_HAS_NMI_SAFE_THIS_CPU_OPS + bool + config HAVE_ALIGNED_STRUCT_PAGE bool help diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 01226e4d960a..4fac088072c3 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -64,6 +64,20 @@ unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); +#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); +#else +static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) +{ + return __srcu_read_lock(ssp); +} +static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) +{ + __srcu_read_unlock(ssp, idx); +} +#endif /* CONFIG_NEED_SRCU_NMI_SAFE */ + #ifdef CONFIG_SRCU void srcu_init(void); #else /* #ifdef CONFIG_SRCU */ @@ -166,6 +180,25 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) return retval; } +/** + * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section, but in an NMI-safe manner. + * See srcu_read_lock() for more information. + */ +static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) +{ + int retval; + + if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) + retval = __srcu_read_lock_nmisafe(ssp); + else + retval = __srcu_read_lock(ssp); + rcu_lock_acquire(&(ssp)->dep_map); + return retval; +} + /* Used by tracing, cannot be traced and cannot invoke lockdep. */ static inline notrace int srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) @@ -191,6 +224,24 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) __srcu_read_unlock(ssp, idx); } +/** + * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * 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) +{ + WARN_ON_ONCE(idx & ~0x1); + rcu_lock_release(&(ssp)->dep_map); + if (IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) + __srcu_read_unlock_nmisafe(ssp, idx); + else + __srcu_read_unlock(ssp, 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) diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index d471d22a5e21..f53ad63b2bc6 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -72,6 +72,9 @@ config TREE_SRCU help This option selects the full-fledged version of SRCU. +config NEED_SRCU_NMI_SAFE + def_bool HAVE_NMI && !ARCH_HAS_NMI_SAFE_THIS_CPU_OPS && !TINY_SRCU + config TASKS_RCU_GENERIC def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU select SRCU diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 503c2aa845a4..b4c74ce10225 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -615,10 +615,14 @@ static struct rcu_torture_ops rcu_busted_ops = { DEFINE_STATIC_SRCU(srcu_ctl); static struct srcu_struct srcu_ctld; static struct srcu_struct *srcu_ctlp = &srcu_ctl; +static struct rcu_torture_ops srcud_ops; static int srcu_torture_read_lock(void) __acquires(srcu_ctlp) { - return srcu_read_lock(srcu_ctlp); + if (cur_ops == &srcud_ops) + return srcu_read_lock_nmisafe(srcu_ctlp); + else + return srcu_read_lock(srcu_ctlp); } static void @@ -642,7 +646,10 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp) { - srcu_read_unlock(srcu_ctlp, idx); + if (cur_ops == &srcud_ops) + srcu_read_unlock_nmisafe(srcu_ctlp, idx); + else + srcu_read_unlock(srcu_ctlp, idx); } static int torture_srcu_read_lock_held(void) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 25e9458da6a2..32a94b254d29 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -654,6 +654,41 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx) } EXPORT_SYMBOL_GPL(__srcu_read_unlock); +#ifdef CONFIG_NEED_SRCU_NMI_SAFE + +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct, but in an NMI-safe manner using RMW atomics. + * Returns an index that must be passed to the matching srcu_read_unlock(). + */ +int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) +{ + int idx; + struct srcu_data *sdp = raw_cpu_ptr(ssp->sda); + + idx = READ_ONCE(ssp->srcu_idx) & 0x1; + atomic_long_inc(&sdp->srcu_lock_count[idx]); + smp_mb__after_atomic(); /* B */ /* Avoid leaking the critical section. */ + return idx; +} +EXPORT_SYMBOL_GPL(__srcu_read_lock_nmisafe); + +/* + * Removes the count for the old reader from the appropriate per-CPU + * element of the srcu_struct. Note that this may well be a different + * CPU than that which was incremented by the corresponding srcu_read_lock(). + */ +void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) +{ + struct srcu_data *sdp = raw_cpu_ptr(ssp->sda); + + smp_mb__before_atomic(); /* C */ /* Avoid leaking the critical section. */ + atomic_long_inc(&sdp->srcu_unlock_count[idx]); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock_nmisafe); + +#endif // CONFIG_NEED_SRCU_NMI_SAFE + /* * Start an SRCU grace period. */ @@ -1090,7 +1125,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp, int ss_state; check_init_srcu_struct(ssp); - idx = srcu_read_lock(ssp); + idx = __srcu_read_lock_nmisafe(ssp); ss_state = smp_load_acquire(&ssp->srcu_size_state); if (ss_state < SRCU_SIZE_WAIT_CALL) sdp = per_cpu_ptr(ssp->sda, 0); @@ -1123,7 +1158,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp, srcu_funnel_gp_start(ssp, sdp, s, do_norm); else if (needexp) srcu_funnel_exp_start(ssp, sdp_mynode, s); - srcu_read_unlock(ssp, idx); + __srcu_read_unlock_nmisafe(ssp, idx); return s; } @@ -1427,13 +1462,13 @@ void srcu_barrier(struct srcu_struct *ssp) /* Initial count prevents reaching zero until all CBs are posted. */ atomic_set(&ssp->srcu_barrier_cpu_cnt, 1); - idx = srcu_read_lock(ssp); + idx = __srcu_read_lock_nmisafe(ssp); if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER) srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, 0)); else for_each_possible_cpu(cpu) srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu)); - srcu_read_unlock(ssp, idx); + __srcu_read_unlock_nmisafe(ssp, idx); /* Remove the initial count, at which point reaching zero can happen. */ if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt)) |