X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=kernel%2Ftrace%2Fring_buffer.c;h=6260717c18e3c6fb8eefa4cfcc185ab8322a6929;hb=d5fb82137b6cd39e67c4321f4f5ce9b03d4d04e6;hp=0315d43176d80d264c37f22ba403a5089a124c48;hpb=1d82b0baf9abd59ae6f53f3102f4e442043763a4;p=karo-tx-linux.git diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 0315d43176d8..6260717c18e3 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3,7 +3,7 @@ * * Copyright (C) 2008 Steven Rostedt */ -#include +#include #include #include #include @@ -115,63 +115,11 @@ int ring_buffer_print_entry_header(struct trace_seq *s) * */ -/* - * A fast way to enable or disable all ring buffers is to - * call tracing_on or tracing_off. Turning off the ring buffers - * prevents all ring buffers from being recorded to. - * Turning this switch on, makes it OK to write to the - * ring buffer, if the ring buffer is enabled itself. - * - * There's three layers that must be on in order to write - * to the ring buffer. - * - * 1) This global flag must be set. - * 2) The ring buffer must be enabled for recording. - * 3) The per cpu buffer must be enabled for recording. - * - * In case of an anomaly, this global flag has a bit set that - * will permantly disable all ring buffers. - */ - -/* - * Global flag to disable all recording to ring buffers - * This has two bits: ON, DISABLED - * - * ON DISABLED - * ---- ---------- - * 0 0 : ring buffers are off - * 1 0 : ring buffers are on - * X 1 : ring buffers are permanently disabled - */ - -enum { - RB_BUFFERS_ON_BIT = 0, - RB_BUFFERS_DISABLED_BIT = 1, -}; - -enum { - RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT, - RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT, -}; - -static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; - /* Used for individual buffers (after the counter) */ #define RB_BUFFER_OFF (1 << 20) #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) -/** - * tracing_off_permanent - permanently disable ring buffers - * - * This function, once called, will disable all ring buffers - * permanently. - */ -void tracing_off_permanent(void) -{ - set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags); -} - #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) #define RB_ALIGNMENT 4U #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) @@ -451,6 +399,23 @@ struct rb_irq_work { bool wakeup_full; }; +/* + * Used for which event context the event is in. + * NMI = 0 + * IRQ = 1 + * SOFTIRQ = 2 + * NORMAL = 3 + * + * See trace_recursive_lock() comment below for more details. + */ +enum { + RB_CTX_NMI, + RB_CTX_IRQ, + RB_CTX_SOFTIRQ, + RB_CTX_NORMAL, + RB_CTX_MAX +}; + /* * head_page == tail_page && head == tail then buffer is empty. */ @@ -462,6 +427,7 @@ struct ring_buffer_per_cpu { arch_spinlock_t lock; struct lock_class_key lock_key; unsigned int nr_pages; + unsigned int current_context; struct list_head *pages; struct buffer_page *head_page; /* read from head */ struct buffer_page *tail_page; /* write to tail */ @@ -2224,7 +2190,7 @@ static unsigned rb_calculate_event_length(unsigned length) /* zero length can cause confusions */ if (!length) - length = 1; + length++; if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) length += sizeof(event.array[0]); @@ -2636,8 +2602,6 @@ rb_reserve_next_event(struct ring_buffer *buffer, return NULL; } -#ifdef CONFIG_TRACING - /* * The lock and unlock are done within a preempt disable section. * The current_context per_cpu variable can only be modified @@ -2675,44 +2639,38 @@ rb_reserve_next_event(struct ring_buffer *buffer, * just so happens that it is the same bit corresponding to * the current context. */ -static DEFINE_PER_CPU(unsigned int, current_context); -static __always_inline int trace_recursive_lock(void) +static __always_inline int +trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) { - unsigned int val = __this_cpu_read(current_context); + unsigned int val = cpu_buffer->current_context; int bit; if (in_interrupt()) { if (in_nmi()) - bit = 0; + bit = RB_CTX_NMI; else if (in_irq()) - bit = 1; + bit = RB_CTX_IRQ; else - bit = 2; + bit = RB_CTX_SOFTIRQ; } else - bit = 3; + bit = RB_CTX_NORMAL; if (unlikely(val & (1 << bit))) return 1; val |= (1 << bit); - __this_cpu_write(current_context, val); + cpu_buffer->current_context = val; return 0; } -static __always_inline void trace_recursive_unlock(void) +static __always_inline void +trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) { - __this_cpu_and(current_context, __this_cpu_read(current_context) - 1); + cpu_buffer->current_context &= cpu_buffer->current_context - 1; } -#else - -#define trace_recursive_lock() (0) -#define trace_recursive_unlock() do { } while (0) - -#endif - /** * ring_buffer_lock_reserve - reserve a part of the buffer * @buffer: the ring buffer to reserve from @@ -2735,41 +2693,37 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) struct ring_buffer_event *event; int cpu; - if (ring_buffer_flags != RB_BUFFERS_ON) - return NULL; - /* If we are tracing schedule, we don't want to recurse */ preempt_disable_notrace(); - if (atomic_read(&buffer->record_disabled)) - goto out_nocheck; - - if (trace_recursive_lock()) - goto out_nocheck; + if (unlikely(atomic_read(&buffer->record_disabled))) + goto out; cpu = raw_smp_processor_id(); - if (!cpumask_test_cpu(cpu, buffer->cpumask)) + if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) goto out; cpu_buffer = buffer->buffers[cpu]; - if (atomic_read(&cpu_buffer->record_disabled)) + if (unlikely(atomic_read(&cpu_buffer->record_disabled))) goto out; - if (length > BUF_MAX_DATA_SIZE) + if (unlikely(length > BUF_MAX_DATA_SIZE)) + goto out; + + if (unlikely(trace_recursive_lock(cpu_buffer))) goto out; event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) - goto out; + goto out_unlock; return event; + out_unlock: + trace_recursive_unlock(cpu_buffer); out: - trace_recursive_unlock(); - - out_nocheck: preempt_enable_notrace(); return NULL; } @@ -2859,7 +2813,7 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer, rb_wakeups(buffer, cpu_buffer); - trace_recursive_unlock(); + trace_recursive_unlock(cpu_buffer); preempt_enable_notrace(); @@ -2970,7 +2924,7 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer, out: rb_end_commit(cpu_buffer); - trace_recursive_unlock(); + trace_recursive_unlock(cpu_buffer); preempt_enable_notrace(); @@ -3000,9 +2954,6 @@ int ring_buffer_write(struct ring_buffer *buffer, int ret = -EBUSY; int cpu; - if (ring_buffer_flags != RB_BUFFERS_ON) - return -EBUSY; - preempt_disable_notrace(); if (atomic_read(&buffer->record_disabled)) @@ -3021,9 +2972,12 @@ int ring_buffer_write(struct ring_buffer *buffer, if (length > BUF_MAX_DATA_SIZE) goto out; + if (unlikely(trace_recursive_lock(cpu_buffer))) + goto out; + event = rb_reserve_next_event(buffer, cpu_buffer, length); if (!event) - goto out; + goto out_unlock; body = rb_event_data(event); @@ -3034,6 +2988,10 @@ int ring_buffer_write(struct ring_buffer *buffer, rb_wakeups(buffer, cpu_buffer); ret = 0; + + out_unlock: + trace_recursive_unlock(cpu_buffer); + out: preempt_enable_notrace(); @@ -3860,19 +3818,36 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) } EXPORT_SYMBOL_GPL(ring_buffer_iter_peek); -static inline int rb_ok_to_lock(void) +static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer) { + if (likely(!in_nmi())) { + raw_spin_lock(&cpu_buffer->reader_lock); + return true; + } + /* * If an NMI die dumps out the content of the ring buffer - * do not grab locks. We also permanently disable the ring - * buffer too. A one time deal is all you get from reading - * the ring buffer from an NMI. + * trylock must be used to prevent a deadlock if the NMI + * preempted a task that holds the ring buffer locks. If + * we get the lock then all is fine, if not, then continue + * to do the read, but this can corrupt the ring buffer, + * so it must be permanently disabled from future writes. + * Reading from NMI is a oneshot deal. */ - if (likely(!in_nmi())) - return 1; + if (raw_spin_trylock(&cpu_buffer->reader_lock)) + return true; - tracing_off_permanent(); - return 0; + /* Continue without locking, but disable the ring buffer */ + atomic_inc(&cpu_buffer->record_disabled); + return false; +} + +static inline void +rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked) +{ + if (likely(locked)) + raw_spin_unlock(&cpu_buffer->reader_lock); + return; } /** @@ -3892,21 +3867,18 @@ ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts, struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; struct ring_buffer_event *event; unsigned long flags; - int dolock; + bool dolock; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return NULL; - dolock = rb_ok_to_lock(); again: local_irq_save(flags); - if (dolock) - raw_spin_lock(&cpu_buffer->reader_lock); + dolock = rb_reader_lock(cpu_buffer); event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event && event->type_len == RINGBUF_TYPE_PADDING) rb_advance_reader(cpu_buffer); - if (dolock) - raw_spin_unlock(&cpu_buffer->reader_lock); + rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); if (event && event->type_len == RINGBUF_TYPE_PADDING) @@ -3959,9 +3931,7 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, struct ring_buffer_per_cpu *cpu_buffer; struct ring_buffer_event *event = NULL; unsigned long flags; - int dolock; - - dolock = rb_ok_to_lock(); + bool dolock; again: /* might be called in atomic */ @@ -3972,8 +3942,7 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); - if (dolock) - raw_spin_lock(&cpu_buffer->reader_lock); + dolock = rb_reader_lock(cpu_buffer); event = rb_buffer_peek(cpu_buffer, ts, lost_events); if (event) { @@ -3981,8 +3950,7 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts, rb_advance_reader(cpu_buffer); } - if (dolock) - raw_spin_unlock(&cpu_buffer->reader_lock); + rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); out: @@ -4263,21 +4231,17 @@ int ring_buffer_empty(struct ring_buffer *buffer) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; - int dolock; + bool dolock; int cpu; int ret; - dolock = rb_ok_to_lock(); - /* yes this is racy, but if you don't like the race, lock the buffer */ for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); - if (dolock) - raw_spin_lock(&cpu_buffer->reader_lock); + dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); - if (dolock) - raw_spin_unlock(&cpu_buffer->reader_lock); + rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); if (!ret) @@ -4297,21 +4261,17 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu) { struct ring_buffer_per_cpu *cpu_buffer; unsigned long flags; - int dolock; + bool dolock; int ret; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 1; - dolock = rb_ok_to_lock(); - cpu_buffer = buffer->buffers[cpu]; local_irq_save(flags); - if (dolock) - raw_spin_lock(&cpu_buffer->reader_lock); + dolock = rb_reader_lock(cpu_buffer); ret = rb_per_cpu_empty(cpu_buffer); - if (dolock) - raw_spin_unlock(&cpu_buffer->reader_lock); + rb_reader_unlock(cpu_buffer, dolock); local_irq_restore(flags); return ret; @@ -4349,9 +4309,6 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, ret = -EAGAIN; - if (ring_buffer_flags != RB_BUFFERS_ON) - goto out; - if (atomic_read(&buffer_a->record_disabled)) goto out;