struct buffer_page *bpage, *tmp;
long i;
+ /* Check if the available memory is there first */
+ i = si_mem_available();
+ if (i < nr_pages)
+ return -ENOMEM;
+
for (i = 0; i < nr_pages; i++) {
struct page *page;
/*
tmp_iter_page = first_page;
do {
+ cond_resched();
+
to_remove_page = tmp_iter_page;
rb_inc_page(cpu_buffer, &tmp_iter_page);
* The lock and unlock are done within a preempt disable section.
* The current_context per_cpu variable can only be modified
* by the current task between lock and unlock. But it can
- * be modified more than once via an interrupt. There are four
- * different contexts that we need to consider.
+ * be modified more than once via an interrupt. To pass this
+ * information from the lock to the unlock without having to
+ * access the 'in_interrupt()' functions again (which do show
+ * a bit of overhead in something as critical as function tracing,
+ * we use a bitmask trick.
+ *
+ * bit 0 = NMI context
+ * bit 1 = IRQ context
+ * bit 2 = SoftIRQ context
+ * bit 3 = normal context.
+ *
+ * This works because this is the order of contexts that can
+ * preempt other contexts. A SoftIRQ never preempts an IRQ
+ * context.
*
- * Normal context.
- * SoftIRQ context
- * IRQ context
- * NMI context
+ * When the context is determined, the corresponding bit is
+ * checked and set (if it was set, then a recursion of that context
+ * happened).
*
- * If for some reason the ring buffer starts to recurse, we
- * only allow that to happen at most 4 times (one for each
- * context). If it happens 5 times, then we consider this a
- * recusive loop and do not let it go further.
+ * On unlock, we need to clear this bit. To do so, just subtract
+ * 1 from the current_context and AND it to itself.
+ *
+ * (binary)
+ * 101 - 1 = 100
+ * 101 & 100 = 100 (clearing bit zero)
+ *
+ * 1010 - 1 = 1001
+ * 1010 & 1001 = 1000 (clearing bit 1)
+ *
+ * The least significant bit can be cleared this way, and it
+ * just so happens that it is the same bit corresponding to
+ * the current context.
*/
static __always_inline int
trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
{
- if (cpu_buffer->current_context >= 4)
+ unsigned int val = cpu_buffer->current_context;
+ unsigned long pc = preempt_count();
+ int bit;
+
+ if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET)))
+ bit = RB_CTX_NORMAL;
+ else
+ bit = pc & NMI_MASK ? RB_CTX_NMI :
+ pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ;
+
+ if (unlikely(val & (1 << bit)))
return 1;
- cpu_buffer->current_context++;
- /* Interrupts must see this update */
- barrier();
+ val |= (1 << bit);
+ cpu_buffer->current_context = val;
return 0;
}
static __always_inline void
trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
{
- /* Don't let the dec leak out */
- barrier();
- cpu_buffer->current_context--;
+ cpu_buffer->current_context &= cpu_buffer->current_context - 1;
}
/**
return !atomic_read(&buffer->record_disabled);
}
+/**
+ * ring_buffer_record_is_set_on - return true if the ring buffer is set writable
+ * @buffer: The ring buffer to see if write is set enabled
+ *
+ * Returns true if the ring buffer is set writable by ring_buffer_record_on().
+ * Note that this does NOT mean it is in a writable state.
+ *
+ * It may return true when the ring buffer has been disabled by
+ * ring_buffer_record_disable(), as that is a temporary disabling of
+ * the ring buffer.
+ */
+int ring_buffer_record_is_set_on(struct ring_buffer *buffer)
+{
+ return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
+}
+
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
* @buffer: The ring buffer to read from
* @cpu: The cpu buffer to iterate over
+ * @flags: gfp flags to use for memory allocation
*
* This performs the initial preparations necessary to iterate
* through the buffer. Memory is allocated, buffer recording
* This overall must be paired with ring_buffer_read_finish.
*/
struct ring_buffer_iter *
-ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
+ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu, gfp_t flags)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_iter *iter;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return NULL;
- iter = kmalloc(sizeof(*iter), GFP_KERNEL);
+ iter = kmalloc(sizeof(*iter), flags);
if (!iter)
return NULL;