diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/rcu.h | 7 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 2 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 12 | ||||
| -rw-r--r-- | kernel/rcu/refscale.c | 250 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 98 | ||||
| -rw-r--r-- | kernel/rcu/tasks.h | 85 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 9 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 639 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 43 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 47 |
11 files changed, 842 insertions, 352 deletions
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index c5aa934de59b..95a0038c9218 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -224,6 +224,7 @@ extern int rcu_cpu_stall_ftrace_dump; extern int rcu_cpu_stall_suppress; extern int rcu_cpu_stall_timeout; extern int rcu_exp_cpu_stall_timeout; +extern bool rcu_exp_stall_task_details __read_mostly; int rcu_jiffies_till_stall_check(void); int rcu_exp_jiffies_till_stall_check(void); @@ -447,14 +448,20 @@ do { \ /* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */ static inline bool rcu_gp_is_normal(void) { return true; } static inline bool rcu_gp_is_expedited(void) { return false; } +static inline bool rcu_async_should_hurry(void) { return false; } static inline void rcu_expedite_gp(void) { } static inline void rcu_unexpedite_gp(void) { } +static inline void rcu_async_hurry(void) { } +static inline void rcu_async_relax(void) { } static inline void rcu_request_urgent_qs_task(struct task_struct *t) { } #else /* #ifdef CONFIG_TINY_RCU */ bool rcu_gp_is_normal(void); /* Internal RCU use. */ bool rcu_gp_is_expedited(void); /* Internal RCU use. */ +bool rcu_async_should_hurry(void); /* Internal RCU use. */ void rcu_expedite_gp(void); void rcu_unexpedite_gp(void); +void rcu_async_hurry(void); +void rcu_async_relax(void); void rcupdate_announce_bootup_oddness(void); #ifdef CONFIG_TASKS_RCU_GENERIC void show_rcu_tasks_gp_kthreads(void); diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index c54ea2b6a36b..f71fac422c8f 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -89,7 +89,7 @@ static void rcu_segcblist_set_len(struct rcu_segcblist *rsclp, long v) } /* Get the length of a segment of the rcu_segcblist structure. */ -static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg) +long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg) { return READ_ONCE(rsclp->seglen[seg]); } diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index 431cee212467..4fe877f5f654 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -15,6 +15,8 @@ static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp) return READ_ONCE(rclp->len); } +long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg); + /* Return number of callbacks in segmented callback list by summing seglen. */ long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp); diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 634df26a2c27..8e6c023212cb 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -399,7 +399,7 @@ static int torture_readlock_not_held(void) return rcu_read_lock_bh_held() || rcu_read_lock_sched_held(); } -static int rcu_torture_read_lock(void) __acquires(RCU) +static int rcu_torture_read_lock(void) { rcu_read_lock(); return 0; @@ -441,7 +441,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) } } -static void rcu_torture_read_unlock(int idx) __releases(RCU) +static void rcu_torture_read_unlock(int idx) { rcu_read_unlock(); } @@ -625,7 +625,7 @@ 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) +static int srcu_torture_read_lock(void) { if (cur_ops == &srcud_ops) return srcu_read_lock_nmisafe(srcu_ctlp); @@ -652,7 +652,7 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) } } -static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp) +static void srcu_torture_read_unlock(int idx) { if (cur_ops == &srcud_ops) srcu_read_unlock_nmisafe(srcu_ctlp, idx); @@ -814,13 +814,13 @@ static void synchronize_rcu_trivial(void) } } -static int rcu_torture_read_lock_trivial(void) __acquires(RCU) +static int rcu_torture_read_lock_trivial(void) { preempt_disable(); return 0; } -static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU) +static void rcu_torture_read_unlock_trivial(int idx) { preempt_enable(); } diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 435c884c02b5..afa3e1a2f690 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -76,6 +76,8 @@ torture_param(int, verbose_batched, 0, "Batch verbose debugging printk()s"); // Wait until there are multiple CPUs before starting test. torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_SCALE_TEST) ? 10 : 0, "Holdoff time before test start (s)"); +// Number of typesafe_lookup structures, that is, the degree of concurrency. +torture_param(long, lookup_instances, 0, "Number of typesafe_lookup structures."); // Number of loops per experiment, all readers execute operations concurrently. torture_param(long, loops, 10000, "Number of loops per experiment."); // Number of readers, with -1 defaulting to about 75% of the CPUs. @@ -124,7 +126,7 @@ static int exp_idx; // Operations vector for selecting different types of tests. struct ref_scale_ops { - void (*init)(void); + bool (*init)(void); void (*cleanup)(void); void (*readsection)(const int nloops); void (*delaysection)(const int nloops, const int udl, const int ndl); @@ -162,8 +164,9 @@ static void ref_rcu_delay_section(const int nloops, const int udl, const int ndl } } -static void rcu_sync_scale_init(void) +static bool rcu_sync_scale_init(void) { + return true; } static struct ref_scale_ops rcu_ops = { @@ -315,9 +318,10 @@ static struct ref_scale_ops refcnt_ops = { // Definitions for rwlock static rwlock_t test_rwlock; -static void ref_rwlock_init(void) +static bool ref_rwlock_init(void) { rwlock_init(&test_rwlock); + return true; } static void ref_rwlock_section(const int nloops) @@ -351,9 +355,10 @@ static struct ref_scale_ops rwlock_ops = { // Definitions for rwsem static struct rw_semaphore test_rwsem; -static void ref_rwsem_init(void) +static bool ref_rwsem_init(void) { init_rwsem(&test_rwsem); + return true; } static void ref_rwsem_section(const int nloops) @@ -523,6 +528,237 @@ static struct ref_scale_ops clock_ops = { .name = "clock" }; +//////////////////////////////////////////////////////////////////////// +// +// Methods leveraging SLAB_TYPESAFE_BY_RCU. +// + +// Item to look up in a typesafe manner. Array of pointers to these. +struct refscale_typesafe { + atomic_t rts_refctr; // Used by all flavors + spinlock_t rts_lock; + seqlock_t rts_seqlock; + unsigned int a; + unsigned int b; +}; + +static struct kmem_cache *typesafe_kmem_cachep; +static struct refscale_typesafe **rtsarray; +static long rtsarray_size; +static DEFINE_TORTURE_RANDOM_PERCPU(refscale_rand); +static bool (*rts_acquire)(struct refscale_typesafe *rtsp, unsigned int *start); +static bool (*rts_release)(struct refscale_typesafe *rtsp, unsigned int start); + +// Conditionally acquire an explicit in-structure reference count. +static bool typesafe_ref_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + return atomic_inc_not_zero(&rtsp->rts_refctr); +} + +// Unconditionally release an explicit in-structure reference count. +static bool typesafe_ref_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + if (!atomic_dec_return(&rtsp->rts_refctr)) { + WRITE_ONCE(rtsp->a, rtsp->a + 1); + kmem_cache_free(typesafe_kmem_cachep, rtsp); + } + return true; +} + +// Unconditionally acquire an explicit in-structure spinlock. +static bool typesafe_lock_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + spin_lock(&rtsp->rts_lock); + return true; +} + +// Unconditionally release an explicit in-structure spinlock. +static bool typesafe_lock_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + spin_unlock(&rtsp->rts_lock); + return true; +} + +// Unconditionally acquire an explicit in-structure sequence lock. +static bool typesafe_seqlock_acquire(struct refscale_typesafe *rtsp, unsigned int *start) +{ + *start = read_seqbegin(&rtsp->rts_seqlock); + return true; +} + +// Conditionally release an explicit in-structure sequence lock. Return +// true if this release was successful, that is, if no retry is required. +static bool typesafe_seqlock_release(struct refscale_typesafe *rtsp, unsigned int start) +{ + return !read_seqretry(&rtsp->rts_seqlock, start); +} + +// Do a read-side critical section with the specified delay in +// microseconds and nanoseconds inserted so as to increase probability +// of failure. +static void typesafe_delay_section(const int nloops, const int udl, const int ndl) +{ + unsigned int a; + unsigned int b; + int i; + long idx; + struct refscale_typesafe *rtsp; + unsigned int start; + + for (i = nloops; i >= 0; i--) { + preempt_disable(); + idx = torture_random(this_cpu_ptr(&refscale_rand)) % rtsarray_size; + preempt_enable(); +retry: + rcu_read_lock(); + rtsp = rcu_dereference(rtsarray[idx]); + a = READ_ONCE(rtsp->a); + if (!rts_acquire(rtsp, &start)) { + rcu_read_unlock(); + goto retry; + } + if (a != READ_ONCE(rtsp->a)) { + (void)rts_release(rtsp, start); + rcu_read_unlock(); + goto retry; + } + un_delay(udl, ndl); + // Remember, seqlock read-side release can fail. + if (!rts_release(rtsp, start)) { + rcu_read_unlock(); + goto retry; + } + b = READ_ONCE(rtsp->a); + WARN_ONCE(a != b, "Re-read of ->a changed from %u to %u.\n", a, b); + b = rtsp->b; + rcu_read_unlock(); + WARN_ON_ONCE(a * a != b); + } +} + +// Because the acquisition and release methods are expensive, there +// is no point in optimizing away the un_delay() function's two checks. +// Thus simply define typesafe_read_section() as a simple wrapper around +// typesafe_delay_section(). +static void typesafe_read_section(const int nloops) +{ + typesafe_delay_section(nloops, 0, 0); +} + +// Allocate and initialize one refscale_typesafe structure. +static struct refscale_typesafe *typesafe_alloc_one(void) +{ + struct refscale_typesafe *rtsp; + + rtsp = kmem_cache_alloc(typesafe_kmem_cachep, GFP_KERNEL); + if (!rtsp) + return NULL; + atomic_set(&rtsp->rts_refctr, 1); + WRITE_ONCE(rtsp->a, rtsp->a + 1); + WRITE_ONCE(rtsp->b, rtsp->a * rtsp->a); + return rtsp; +} + +// Slab-allocator constructor for refscale_typesafe structures created +// out of a new slab of system memory. +static void refscale_typesafe_ctor(void *rtsp_in) +{ + struct refscale_typesafe *rtsp = rtsp_in; + + spin_lock_init(&rtsp->rts_lock); + seqlock_init(&rtsp->rts_seqlock); + preempt_disable(); + rtsp->a = torture_random(this_cpu_ptr(&refscale_rand)); + preempt_enable(); +} + +static struct ref_scale_ops typesafe_ref_ops; +static struct ref_scale_ops typesafe_lock_ops; +static struct ref_scale_ops typesafe_seqlock_ops; + +// Initialize for a typesafe test. +static bool typesafe_init(void) +{ + long idx; + long si = lookup_instances; + + typesafe_kmem_cachep = kmem_cache_create("refscale_typesafe", + sizeof(struct refscale_typesafe), sizeof(void *), + SLAB_TYPESAFE_BY_RCU, refscale_typesafe_ctor); + if (!typesafe_kmem_cachep) + return false; + if (si < 0) + si = -si * nr_cpu_ids; + else if (si == 0) + si = nr_cpu_ids; + rtsarray_size = si; + rtsarray = kcalloc(si, sizeof(*rtsarray), GFP_KERNEL); + if (!rtsarray) + return false; + for (idx = 0; idx < rtsarray_size; idx++) { + rtsarray[idx] = typesafe_alloc_one(); + if (!rtsarray[idx]) + return false; + } + if (cur_ops == &typesafe_ref_ops) { + rts_acquire = typesafe_ref_acquire; + rts_release = typesafe_ref_release; + } else if (cur_ops == &typesafe_lock_ops) { + rts_acquire = typesafe_lock_acquire; + rts_release = typesafe_lock_release; + } else if (cur_ops == &typesafe_seqlock_ops) { + rts_acquire = typesafe_seqlock_acquire; + rts_release = typesafe_seqlock_release; + } else { + WARN_ON_ONCE(1); + return false; + } + return true; +} + +// Clean up after a typesafe test. +static void typesafe_cleanup(void) +{ + long idx; + + if (rtsarray) { + for (idx = 0; idx < rtsarray_size; idx++) + kmem_cache_free(typesafe_kmem_cachep, rtsarray[idx]); + kfree(rtsarray); + rtsarray = NULL; + rtsarray_size = 0; + } + kmem_cache_destroy(typesafe_kmem_cachep); + typesafe_kmem_cachep = NULL; + rts_acquire = NULL; + rts_release = NULL; +} + +// The typesafe_init() function distinguishes these structures by address. +static struct ref_scale_ops typesafe_ref_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_ref" +}; + +static struct ref_scale_ops typesafe_lock_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_lock" +}; + +static struct ref_scale_ops typesafe_seqlock_ops = { + .init = typesafe_init, + .cleanup = typesafe_cleanup, + .readsection = typesafe_read_section, + .delaysection = typesafe_delay_section, + .name = "typesafe_seqlock" +}; + static void rcu_scale_one_reader(void) { if (readdelay <= 0) @@ -812,6 +1048,7 @@ ref_scale_init(void) static struct ref_scale_ops *scale_ops[] = { &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, + &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops, }; if (!torture_init_begin(scale_type, verbose)) @@ -833,7 +1070,10 @@ ref_scale_init(void) goto unwind; } if (cur_ops->init) - cur_ops->init(); + if (!cur_ops->init()) { + firsterr = -EUCLEAN; + goto unwind; + } ref_scale_print_module_parms(cur_ops, "Start of test"); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index ca4b5dcec675..ab4ee58af84b 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -154,7 +154,7 @@ static void init_srcu_struct_data(struct srcu_struct *ssp) */ static inline bool srcu_invl_snp_seq(unsigned long s) { - return rcu_seq_state(s) == SRCU_SNP_INIT_SEQ; + return s == SRCU_SNP_INIT_SEQ; } /* @@ -469,24 +469,59 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) /* * If the locks are the same as the unlocks, then there must have - * been no readers on this index at some time in between. This does - * not mean that there are no more readers, as one could have read - * the current index but not have incremented the lock counter yet. + * been no readers on this index at some point in this function. + * But there might be more readers, as a task might have read + * the current ->srcu_idx but not yet have incremented its CPU's + * ->srcu_lock_count[idx] counter. In fact, it is possible + * that most of the tasks have been preempted between fetching + * ->srcu_idx and incrementing ->srcu_lock_count[idx]. And there + * could be almost (ULONG_MAX / sizeof(struct task_struct)) tasks + * in a system whose address space was fully populated with memory. + * Call this quantity Nt. * - * So suppose that the updater is preempted here for so long - * that more than ULONG_MAX non-nested readers come and go in - * the meantime. It turns out that this cannot result in overflow - * because if a reader modifies its unlock count after we read it - * above, then that reader's next load of ->srcu_idx is guaranteed - * to get the new value, which will cause it to operate on the - * other bank of counters, where it cannot contribute to the - * overflow of these counters. This means that there is a maximum - * of 2*NR_CPUS increments, which cannot overflow given current - * systems, especially not on 64-bit systems. + * So suppose that the updater is preempted at this point in the + * code for a long time. That now-preempted updater has already + * flipped ->srcu_idx (possibly during the preceding grace period), + * done an smp_mb() (again, possibly during the preceding grace + * period), and summed up the ->srcu_unlock_count[idx] counters. + * How many times can a given one of the aforementioned Nt tasks + * increment the old ->srcu_idx value's ->srcu_lock_count[idx] + * counter, in the absence of nesting? * - * OK, how about nesting? This does impose a limit on nesting - * of floor(ULONG_MAX/NR_CPUS/2), which should be sufficient, - * especially on 64-bit systems. + * It can clearly do so once, given that it has already fetched + * the old value of ->srcu_idx and is just about to use that value + * to index its increment of ->srcu_lock_count[idx]. But as soon as + * it leaves that SRCU read-side critical section, it will increment + * ->srcu_unlock_count[idx], which must follow the updater's above + * read from that same value. Thus, as soon the reading task does + * an smp_mb() and a later fetch from ->srcu_idx, that task will be + * guaranteed to get the new index. Except that the increment of + * ->srcu_unlock_count[idx] in __srcu_read_unlock() is after the + * smp_mb(), and the fetch from ->srcu_idx in __srcu_read_lock() + * is before the smp_mb(). Thus, that task might not see the new + * value of ->srcu_idx until the -second- __srcu_read_lock(), + * which in turn means that this task might well increment + * ->srcu_lock_count[idx] for the old value of ->srcu_idx twice, + * not just once. + * + * However, it is important to note that a given smp_mb() takes + * effect not just for the task executing it, but also for any + * later task running on that same CPU. + * + * That is, there can be almost Nt + Nc further increments of + * ->srcu_lock_count[idx] for the old index, where Nc is the number + * of CPUs. But this is OK because the size of the task_struct + * structure limits the value of Nt and current systems limit Nc + * to a few thousand. + * + * OK, but what about nesting? This does impose a limit on + * nesting of half of the size of the task_struct structure + * (measured in bytes), which should be sufficient. A late 2022 + * TREE01 rcutorture run reported this size to be no less than + * 9408 bytes, allowing up to 4704 levels of nesting, which is + * comfortably beyond excessive. Especially on 64-bit systems, + * which are unlikely to be configured with an address space fully + * populated with memory, at least not anytime soon. */ return srcu_readers_lock_idx(ssp, idx) == unlocks; } @@ -726,7 +761,7 @@ static void srcu_gp_start(struct srcu_struct *ssp) int state; if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER) - sdp = per_cpu_ptr(ssp->sda, 0); + sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id()); else sdp = this_cpu_ptr(ssp->sda); lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock)); @@ -837,7 +872,8 @@ static void srcu_gp_end(struct srcu_struct *ssp) /* Initiate callback invocation as needed. */ ss_state = smp_load_acquire(&ssp->srcu_size_state); if (ss_state < SRCU_SIZE_WAIT_BARRIER) { - srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, 0), cbdelay); + srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, get_boot_cpu_id()), + cbdelay); } else { idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); srcu_for_each_node_breadth_first(ssp, snp) { @@ -914,7 +950,7 @@ static void srcu_funnel_exp_start(struct srcu_struct *ssp, struct srcu_node *snp if (snp) for (; snp != NULL; snp = snp->srcu_parent) { sgsne = READ_ONCE(snp->srcu_gp_seq_needed_exp); - if (rcu_seq_done(&ssp->srcu_gp_seq, s) || + if (WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) || (!srcu_invl_snp_seq(sgsne) && ULONG_CMP_GE(sgsne, s))) return; spin_lock_irqsave_rcu_node(snp, flags); @@ -941,6 +977,9 @@ static void srcu_funnel_exp_start(struct srcu_struct *ssp, struct srcu_node *snp * * Note that this function also does the work of srcu_funnel_exp_start(), * in some cases by directly invoking it. + * + * The srcu read lock should be hold around this function. And s is a seq snap + * after holding that lock. */ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, unsigned long s, bool do_norm) @@ -961,7 +1000,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, if (snp_leaf) /* Each pass through the loop does one level of the srcu_node tree. */ for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) { - if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != snp_leaf) + if (WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) && snp != snp_leaf) return; /* GP already done and CBs recorded. */ spin_lock_irqsave_rcu_node(snp, flags); snp_seq = snp->srcu_have_cbs[idx]; @@ -998,8 +1037,8 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, if (!do_norm && ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s)) WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s); - /* If grace period not already done and none in progress, start it. */ - if (!rcu_seq_done(&ssp->srcu_gp_seq, s) && + /* If grace period not already in progress, start it. */ + if (!WARN_ON_ONCE(rcu_seq_done(&ssp->srcu_gp_seq, s)) && rcu_seq_state(ssp->srcu_gp_seq) == SRCU_STATE_IDLE) { WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)); srcu_gp_start(ssp); @@ -1059,10 +1098,11 @@ static void srcu_flip(struct srcu_struct *ssp) /* * Ensure that if the updater misses an __srcu_read_unlock() - * increment, that task's next __srcu_read_lock() will see the - * above counter update. Note that both this memory barrier - * and the one in srcu_readers_active_idx_check() provide the - * guarantee for __srcu_read_lock(). + * increment, that task's __srcu_read_lock() following its next + * __srcu_read_lock() or __srcu_read_unlock() will see the above + * counter update. Note that both this memory barrier and the + * one in srcu_readers_active_idx_check() provide the guarantee + * for __srcu_read_lock(). */ smp_mb(); /* D */ /* Pairs with C. */ } @@ -1161,7 +1201,7 @@ static unsigned long srcu_gp_start_if_needed(struct srcu_struct *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); + sdp = per_cpu_ptr(ssp->sda, get_boot_cpu_id()); else sdp = raw_cpu_ptr(ssp->sda); spin_lock_irqsave_sdp_contention(sdp, &flags); @@ -1497,7 +1537,7 @@ void srcu_barrier(struct srcu_struct *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)); + srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, get_boot_cpu_id())); else for_each_possible_cpu(cpu) srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu)); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fe9840d90e96..bfb5e1549f2b 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -384,6 +384,7 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) { int cpu; unsigned long flags; + bool gpdone = poll_state_synchronize_rcu(rtp->percpu_dequeue_gpseq); long n; long ncbs = 0; long ncbsnz = 0; @@ -425,21 +426,23 @@ static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp) WRITE_ONCE(rtp->percpu_enqueue_shift, order_base_2(nr_cpu_ids)); smp_store_release(&rtp->percpu_enqueue_lim, 1); rtp->percpu_dequeue_gpseq = get_state_synchronize_rcu(); + gpdone = false; pr_info("Starting switch %s to CPU-0 callback queuing.\n", rtp->name); } raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags); } - if (rcu_task_cb_adjust && !ncbsnz && - poll_state_synchronize_rcu(rtp->percpu_dequeue_gpseq)) { + if (rcu_task_cb_adjust && !ncbsnz && gpdone) { raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags); if (rtp->percpu_enqueue_lim < rtp->percpu_dequeue_lim) { WRITE_ONCE(rtp->percpu_dequeue_lim, 1); pr_info("Completing switch %s to CPU-0 callback queuing.\n", rtp->name); } - for (cpu = rtp->percpu_dequeue_lim; cpu < nr_cpu_ids; cpu++) { - struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); + if (rtp->percpu_dequeue_lim == 1) { + for (cpu = rtp->percpu_dequeue_lim; cpu < nr_cpu_ids; cpu++) { + struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu); - WARN_ON_ONCE(rcu_segcblist_n_cbs(&rtpcp->cblist)); + WARN_ON_ONCE(rcu_segcblist_n_cbs(&rtpcp->cblist)); + } } raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags); } @@ -560,8 +563,9 @@ static int __noreturn rcu_tasks_kthread(void *arg) static void synchronize_rcu_tasks_generic(struct rcu_tasks *rtp) { /* Complain if the scheduler has not started. */ - WARN_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE, - "synchronize_rcu_tasks called too soon"); + if (WARN_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE, + "synchronize_%s() called too soon", rtp->name)) + return; // If the grace-period kthread is running, use it. if (READ_ONCE(rtp->kthread_ptr)) { @@ -827,11 +831,21 @@ static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop) static void rcu_tasks_postscan(struct list_head *hop) { /* - * Wait for tasks that are in the process of exiting. This - * does only part of the job, ensuring that all tasks that were - * previously exiting reach the point where they have disabled - * preemption, allowing the later synchronize_rcu() to finish - * the job. + * Exiting tasks may escape the tasklist scan. Those are vulnerable + * until their final schedule() with TASK_DEAD state. To cope with + * this, divide the fragile exit path part in two intersecting + * read side critical sections: + * + * 1) An _SRCU_ read side starting before calling exit_notify(), + * which may remove the task from the tasklist, and ending after + * the final preempt_disable() call in do_exit(). + * + * 2) An _RCU_ read side starting with the final preempt_disable() + * call in do_exit() and ending with the final call to schedule() + * with TASK_DEAD state. + * + * This handles the part 1). And postgp will handle part 2) with a + * call to synchronize_rcu(). */ synchronize_srcu(&tasks_rcu_exit_srcu); } @@ -898,7 +912,10 @@ static void rcu_tasks_postgp(struct rcu_tasks *rtp) * * In addition, this synchronize_rcu() waits for exiting tasks * to complete their final preempt_disable() region of execution, - * cleaning up after the synchronize_srcu() above. + * cleaning up after synchronize_srcu(&tasks_rcu_exit_srcu), + * enforcing the whole region before tasklist removal until + * the final schedule() with TASK_DEAD state to be an RCU TASKS + * read side critical section. */ synchronize_rcu(); } @@ -988,27 +1005,42 @@ void show_rcu_tasks_classic_gp_kthread(void) EXPORT_SYMBOL_GPL(show_rcu_tasks_classic_gp_kthread); #endif // !defined(CONFIG_TINY_RCU) -/* Do the srcu_read_lock() for the above synchronize_srcu(). */ +/* + * Contribute to protect against tasklist scan blind spot while the + * task is exiting and may be removed from the tasklist. See + * corresponding synchronize_srcu() for further details. + */ void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu) { - preempt_disable(); current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu); - preempt_enable(); } -/* Do the srcu_read_unlock() for the above synchronize_srcu(). */ -void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu) +/* + * Contribute to protect against tasklist scan blind spot while the + * task is exiting and may be removed from the tasklist. See + * corresponding synchronize_srcu() for further details. + */ +void exit_tasks_rcu_stop(void) __releases(&tasks_rcu_exit_srcu) { struct task_struct *t = current; - preempt_disable(); __srcu_read_unlock(&tasks_rcu_exit_srcu, t->rcu_tasks_idx); - preempt_enable(); - exit_tasks_rcu_finish_trace(t); +} + +/* + * Contribute to protect against tasklist scan blind spot while the + * task is exiting and may be removed from the tasklist. See + * corresponding synchronize_srcu() for further details. + */ +void exit_tasks_rcu_finish(void) +{ + exit_tasks_rcu_stop(); + exit_tasks_rcu_finish_trace(current); } #else /* #ifdef CONFIG_TASKS_RCU */ void exit_tasks_rcu_start(void) { } +void exit_tasks_rcu_stop(void) { } void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); } #endif /* #else #ifdef CONFIG_TASKS_RCU */ @@ -1036,9 +1068,6 @@ static void rcu_tasks_be_rude(struct work_struct *work) // Wait for one rude RCU-tasks grace period. static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp) { - if (num_online_cpus() <= 1) - return; // Fastpath for only one CPU. - rtp->n_ipis += cpumask_weight(cpu_online_mask); schedule_on_each_cpu(rcu_tasks_be_rude); } @@ -1815,23 +1844,21 @@ static void test_rcu_tasks_callback(struct rcu_head *rhp) static void rcu_tasks_initiate_self_tests(void) { - unsigned long j = jiffies; - pr_info("Running RCU-tasks wait API self tests\n"); #ifdef CONFIG_TASKS_RCU - tests[0].runstart = j; + tests[0].runstart = jiffies; synchronize_rcu_tasks(); call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback); #endif #ifdef CONFIG_TASKS_RUDE_RCU - tests[1].runstart = j; + tests[1].runstart = jiffies; synchronize_rcu_tasks_rude(); call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback); #endif #ifdef CONFIG_TASKS_TRACE_RCU - tests[2].runstart = j; + tests[2].runstart = jiffies; synchronize_rcu_tasks_trace(); call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback); #endif diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 72913ce21258..42f7589e51e0 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -246,15 +246,12 @@ bool poll_state_synchronize_rcu(unsigned long oldstate) EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu); #ifdef CONFIG_KASAN_GENERIC -void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) +void kvfree_call_rcu(struct rcu_head *head, void *ptr) { - if (head) { - void *ptr = (void *) head - (unsigned long) func; - + if (head) kasan_record_aux_stack_noalloc(ptr); - } - __kvfree_call_rcu(head, func); + __kvfree_call_rcu(head, ptr); } EXPORT_SYMBOL_GPL(kvfree_call_rcu); #endif diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index cf34a961821a..739219a78b84 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -144,14 +144,16 @@ static int rcu_scheduler_fully_active __read_mostly; static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, unsigned long gps, unsigned long flags); -static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); -static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); static void invoke_rcu_core(void); static void rcu_report_exp_rdp(struct rcu_data *rdp); static void sync_sched_exp_online_cleanup(int cpu); static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp); static bool rcu_rdp_is_offloaded(struct rcu_data *rdp); +static bool rcu_rdp_cpu_online(struct rcu_data *rdp); +static bool rcu_init_invoked(void); +static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); +static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); /* * rcuc/rcub/rcuop kthread realtime priority. The "rcuop" @@ -215,27 +217,6 @@ EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio); #define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays for debugging. */ /* - * Compute the mask of online CPUs for the specified rcu_node structure. - * This will not be stable unless the rcu_node structure's ->lock is - * held, but the bit corresponding to the current CPU will be stable - * in most contexts. - */ -static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) -{ - return READ_ONCE(rnp->qsmaskinitnext); -} - -/* - * Is the CPU corresponding to the specified rcu_data structure online - * from RCU's perspective? This perspective is given by that structure's - * ->qsmaskinitnext field rather than by the global cpu_online_mask. - */ -static bool rcu_rdp_cpu_online(struct rcu_data *rdp) -{ - return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode)); -} - -/* * Return true if an RCU grace period is in progress. The READ_ONCE()s * permit this function to be invoked without holding the root rcu_node * structure's ->lock, but of course results can be subject to change. @@ -734,46 +715,6 @@ void rcu_request_urgent_qs_task(struct task_struct *t) smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true); } -#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) - -/* - * Is the current CPU online as far as RCU is concerned? - * - * Disable preemption to avoid false positives that could otherwise - * happen due to the current CPU number being sampled, this task being - * preempted, its old CPU being taken offline, resuming on some other CPU, - * then determining that its old CPU is now offline. - * - * Disable checking if in an NMI handler because we cannot safely - * report errors from NMI handlers anyway. In addition, it is OK to use</ |