*
*/
-/*
- * 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)
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.
*/
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 */
/* 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]);
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
* 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
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;
}
rb_wakeups(buffer, cpu_buffer);
- trace_recursive_unlock();
+ trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
out:
rb_end_commit(cpu_buffer);
- trace_recursive_unlock();
+ trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
int ret = -EBUSY;
int cpu;
- if (ring_buffer_flags != RB_BUFFERS_ON)
- return -EBUSY;
-
preempt_disable_notrace();
if (atomic_read(&buffer->record_disabled))
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);
rb_wakeups(buffer, cpu_buffer);
ret = 0;
+
+ out_unlock:
+ trace_recursive_unlock(cpu_buffer);
+
out:
preempt_enable_notrace();
}
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;
}
/**
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)
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 */
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) {
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:
{
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)
{
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;
ret = -EAGAIN;
- if (ring_buffer_flags != RB_BUFFERS_ON)
- goto out;
-
if (atomic_read(&buffer_a->record_disabled))
goto out;
projects / karo-tx-linux.git / blobdiff