19 files changed, 332 insertions, 186 deletions

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 1b12696cca06..ce1f3e44c24f 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -586,7 +586,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
                 return;
         }
 
-        if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
+        if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) {
                 *parent = old;
                 return;
         }
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 82ddfd3a75af..3e298e64f0db 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -190,7 +190,7 @@ unsigned long prepare_ftrace_return(unsigned long ip, unsigned long parent)
                 goto out;
         if (unlikely(atomic_read(&current->tracing_graph_pause)))
                 goto out;
-        if (ftrace_push_return_trace(parent, ip, &trace.depth) == -EBUSY)
+        if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
                 goto out;
         trace.func = ftrace_mcount_call_adjust(ip) & PSW_ADDR_INSN;
         /* Only trace if the calling function expects to. */
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 73c0bda73fcd..d1430ef6b4f9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -34,6 +34,7 @@ config X86
         select HAVE_DYNAMIC_FTRACE
         select HAVE_FUNCTION_TRACER
         select HAVE_FUNCTION_GRAPH_TRACER
+        select HAVE_FUNCTION_GRAPH_FP_TEST
         select HAVE_FUNCTION_TRACE_MCOUNT_TEST
         select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
         select HAVE_FTRACE_SYSCALLS
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 9f8ce77dbc64..c097e7d607c6 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1174,6 +1174,7 @@ ENTRY(ftrace_graph_caller)
         pushl %edx
         movl 0xc(%esp), %edx
         lea 0x4(%ebp), %eax
+        movl (%ebp), %ecx
         subl $MCOUNT_INSN_SIZE, %edx
         call prepare_ftrace_return
         popl %edx
@@ -1188,6 +1189,7 @@ return_to_handler:
         pushl %eax
         pushl %ecx
         pushl %edx
+        movl %ebp, %eax
         call ftrace_return_to_handler
         movl %eax, 0xc(%esp)
         popl %edx
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index de74f0a3e0ed..c251be745107 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -135,6 +135,7 @@ ENTRY(ftrace_graph_caller)
 
         leaq 8(%rbp), %rdi
         movq 0x38(%rsp), %rsi
+        movq (%rbp), %rdx
         subq $MCOUNT_INSN_SIZE, %rsi
 
         call    prepare_ftrace_return
@@ -150,6 +151,7 @@ GLOBAL(return_to_handler)
         /* Save the return values */
         movq %rax, (%rsp)
         movq %rdx, 8(%rsp)
+        movq %rbp, %rdi
 
         call ftrace_return_to_handler
 
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index b79c5533c421..d94e1ea3b9fe 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -408,7 +408,8 @@ int ftrace_disable_ftrace_graph_caller(void)
  * Hook the return address and push it in the stack of return addrs
  * in current thread info.
  */
-void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+                           unsigned long frame_pointer)
 {
         unsigned long old;
         int faulted;
@@ -453,7 +454,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
                 return;
         }
 
-        if (ftrace_push_return_trace(old, self_addr, &trace.depth) == -EBUSY) {
+        if (ftrace_push_return_trace(old, self_addr, &trace.depth,
+                    frame_pointer) == -EBUSY) {
                 *parent = old;
                 return;
         }
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 39b95c56587e..dc3b1328aaeb 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -362,6 +362,7 @@ struct ftrace_ret_stack {
         unsigned long func;
         unsigned long long calltime;
         unsigned long long subtime;
+        unsigned long fp;
 };
 
 /*
@@ -372,7 +373,8 @@ struct ftrace_ret_stack {
 extern void return_to_handler(void);
 
 extern int
-ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth);
+ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
+                         unsigned long frame_pointer);
 
 /*
  * Sometimes we don't want to trace a function with the function
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index c68bccba2074..c134dd1fe6b6 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -3,6 +3,8 @@
 
 #include <linux/fs.h>
 
+#include <asm/page.h>
+
 /*
  * Trace sequences are used to allow a function to call several other functions
  * to create a string of data to use (up to a max of PAGE_SIZE.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 61071fecc82e..1551f47e7669 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -18,6 +18,13 @@ config HAVE_FUNCTION_TRACER
 config HAVE_FUNCTION_GRAPH_TRACER
         bool
 
+config HAVE_FUNCTION_GRAPH_FP_TEST
+        bool
+        help
+         An arch may pass in a unique value (frame pointer) to both the
+         entering and exiting of a function. On exit, the value is compared
+         and if it does not match, then it will panic the kernel.
+
 config HAVE_FUNCTION_TRACE_MCOUNT_TEST
         bool
         help
@@ -121,6 +128,7 @@ config FUNCTION_GRAPH_TRACER
         bool "Kernel Function Graph Tracer"
         depends on HAVE_FUNCTION_GRAPH_TRACER
         depends on FUNCTION_TRACER
+        depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
         default y
         help
           Enable the kernel to trace a function at both its return
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index bb60732ade0c..3718d55fb4c3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1224,6 +1224,13 @@ static void ftrace_shutdown(int command)
                 return;
 
         ftrace_start_up--;
+        /*
+         * Just warn in case of unbalance, no need to kill ftrace, it's not
+         * critical but the ftrace_call callers may be never nopped again after
+         * further ftrace uses.
+         */
+        WARN_ON_ONCE(ftrace_start_up < 0);
+
         if (!ftrace_start_up)
                 command |= FTRACE_DISABLE_CALLS;
 
diff --git a/kernel/trace/kmemtrace.c b/kernel/trace/kmemtrace.c
index 86cdf671d7e2..1edaa9516e81 100644
--- a/kernel/trace/kmemtrace.c
+++ b/kernel/trace/kmemtrace.c
@@ -186,7 +186,7 @@ static int kmem_trace_init(struct trace_array *tr)
         int cpu;
         kmemtrace_array = tr;
 
-        for_each_cpu_mask(cpu, cpu_possible_map)
+        for_each_cpu(cpu, cpu_possible_mask)
                 tracing_reset(tr, cpu);
 
         kmemtrace_start_probes();
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index dc4dc70171ce..04dac2638258 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -206,6 +206,7 @@ EXPORT_SYMBOL_GPL(tracing_is_on);
 #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)
+#define RB_EVNT_MIN_SIZE        8U      /* two 32bit words */
 
 /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
 #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
@@ -415,6 +416,8 @@ struct ring_buffer_per_cpu {
         unsigned long                   overrun;
         unsigned long                   read;
         local_t                         entries;
+        local_t                         committing;
+        local_t                         commits;
         u64                             write_stamp;
         u64                             read_stamp;
         atomic_t                        record_disabled;
@@ -618,12 +621,6 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
         kfree(cpu_buffer);
 }
 
-/*
- * Causes compile errors if the struct buffer_page gets bigger
- * than the struct page.
- */
-extern int ring_buffer_page_too_big(void);
-
 #ifdef CONFIG_HOTPLUG_CPU
 static int rb_cpu_notify(struct notifier_block *self,
                          unsigned long action, void *hcpu);
@@ -646,11 +643,6 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         int bsize;
         int cpu;
 
-        /* Paranoid! Optimizes out when all is well */
-        if (sizeof(struct buffer_page) > sizeof(struct page))
-                ring_buffer_page_too_big();
-
-
         /* keep it in its own cache line */
         buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
                          GFP_KERNEL);
@@ -666,8 +658,8 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
         buffer->reader_lock_key = key;
 
         /* need at least two pages */
-        if (buffer->pages == 1)
-                buffer->pages++;
+        if (buffer->pages < 2)
+                buffer->pages = 2;
 
         /*
          * In case of non-hotplug cpu, if the ring-buffer is allocated
@@ -1011,12 +1003,12 @@ rb_event_index(struct ring_buffer_event *event)
 {
         unsigned long addr = (unsigned long)event;
 
-        return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
+        return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
 }
 
 static inline int
-rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
-             struct ring_buffer_event *event)
+rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
+                   struct ring_buffer_event *event)
 {
         unsigned long addr = (unsigned long)event;
         unsigned long index;
@@ -1029,31 +1021,6 @@ rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
 }
 
 static void
-rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
-                    struct ring_buffer_event *event)
-{
-        unsigned long addr = (unsigned long)event;
-        unsigned long index;
-
-        index = rb_event_index(event);
-        addr &= PAGE_MASK;
-
-        while (cpu_buffer->commit_page->page != (void *)addr) {
-                if (RB_WARN_ON(cpu_buffer,
-                          cpu_buffer->commit_page == cpu_buffer->tail_page))
-                        return;
-                cpu_buffer->commit_page->page->commit =
-                        cpu_buffer->commit_page->write;
-                rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
-                cpu_buffer->write_stamp =
-                        cpu_buffer->commit_page->page->time_stamp;
-        }
-
-        /* Now set the commit to the event's index */
-        local_set(&cpu_buffer->commit_page->page->commit, index);
-}
-
-static void
 rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
 {
         /*
@@ -1171,6 +1138,60 @@ static unsigned rb_calculate_event_length(unsigned length)
         return length;
 }
 
+static inline void
+rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
+              struct buffer_page *tail_page,
+              unsigned long tail, unsigned long length)
+{
+        struct ring_buffer_event *event;
+
+        /*
+         * Only the event that crossed the page boundary
+         * must fill the old tail_page with padding.
+         */
+        if (tail >= BUF_PAGE_SIZE) {
+                local_sub(length, &tail_page->write);
+                return;
+        }
+
+        event = __rb_page_index(tail_page, tail);
+        kmemcheck_annotate_bitfield(event, bitfield);
+
+        /*
+         * If this event is bigger than the minimum size, then
+         * we need to be careful that we don't subtract the
+         * write counter enough to allow another writer to slip
+         * in on this page.
+         * We put in a discarded commit instead, to make sure
+         * that this space is not used again.
+         *
+         * If we are less than the minimum size, we don't need to
+         * worry about it.
+         */
+        if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
+                /* No room for any events */
+
+                /* Mark the rest of the page with padding */
+                rb_event_set_padding(event);
+
+                /* Set the write back to the previous setting */
+                local_sub(length, &tail_page->write);
+                return;
+        }
+
+        /* Put in a discarded event */
+        event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
+        event->type_len = RINGBUF_TYPE_PADDING;
+        /* time delta must be non zero */
+        event->time_delta = 1;
+        /* Account for this as an entry */
+        local_inc(&tail_page->entries);
+        local_inc(&cpu_buffer->entries);
+
+        /* Set write to end of buffer */
+        length = (tail + length) - BUF_PAGE_SIZE;
+        local_sub(length, &tail_page->write);
+}
 
 static struct ring_buffer_event *
 rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
@@ -1180,7 +1201,6 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 {
         struct buffer_page *next_page, *head_page, *reader_page;
         struct ring_buffer *buffer = cpu_buffer->buffer;
-        struct ring_buffer_event *event;
         bool lock_taken = false;
         unsigned long flags;
 
@@ -1265,27 +1285,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
                 cpu_buffer->tail_page->page->time_stamp = *ts;
         }
 
-        /*
-         * The actual tail page has moved forward.
-         */
-        if (tail < BUF_PAGE_SIZE) {
-                /* Mark the rest of the page with padding */
-                event = __rb_page_index(tail_page, tail);
-                kmemcheck_annotate_bitfield(event, bitfield);
-                rb_event_set_padding(event);
-        }
-
-        /* Set the write back to the previous setting */
-        local_sub(length, &tail_page->write);
-
-        /*
-         * If this was a commit entry that failed,
-         * increment that too
-         */
-        if (tail_page == cpu_buffer->commit_page &&
-            tail == rb_commit_index(cpu_buffer)) {
-                rb_set_commit_to_write(cpu_buffer);
-        }
+        rb_reset_tail(cpu_buffer, tail_page, tail, length);
 
         __raw_spin_unlock(&cpu_buffer->lock);
         local_irq_restore(flags);
@@ -1295,7 +1295,7 @@ rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
 
  out_reset:
         /* reset write */
-        local_sub(length, &tail_page->write);
+        rb_reset_tail(cpu_buffer, tail_page, tail, length);
 
         if (likely(lock_taken))
                 __raw_spin_unlock(&cpu_buffer->lock);
@@ -1325,9 +1325,6 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 
         /* We reserved something on the buffer */
 
-        if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
-                return NULL;
-
         event = __rb_page_index(tail_page, tail);
         kmemcheck_annotate_bitfield(event, bitfield);
         rb_update_event(event, type, length);
@@ -1337,11 +1334,11 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
                 local_inc(&tail_page->entries);
 
         /*
-         * If this is a commit and the tail is zero, then update
-         * this page's time stamp.
+         * If this is the first commit on the page, then update
+         * its timestamp.
          */
-        if (!tail && rb_is_commit(cpu_buffer, event))
-                cpu_buffer->commit_page->page->time_stamp = *ts;
+        if (!tail)
+                tail_page->page->time_stamp = *ts;
 
         return event;
 }
@@ -1410,16 +1407,16 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
                 return -EAGAIN;
 
         /* Only a commited time event can update the write stamp */
-        if (rb_is_commit(cpu_buffer, event)) {
+        if (rb_event_is_commit(cpu_buffer, event)) {
                 /*
-                 * If this is the first on the page, then we need to
-                 * update the page itself, and just put in a zero.
+                 * If this is the first on the page, then it was
+                 * updated with the page itself. Try to discard it
+                 * and if we can't just make it zero.
                  */
                 if (rb_event_index(event)) {
                         event->time_delta = *delta & TS_MASK;
                         event->array[0] = *delta >> TS_SHIFT;
                 } else {
-                        cpu_buffer->commit_page->page->time_stamp = *ts;
                         /* try to discard, since we do not need this */
                         if (!rb_try_to_discard(cpu_buffer, event)) {
                                 /* nope, just zero it */
@@ -1445,6 +1442,44 @@ rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
         return ret;
 }
 
+static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+        local_inc(&cpu_buffer->committing);
+        local_inc(&cpu_buffer->commits);
+}
+
+static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+        unsigned long commits;
+
+        if (RB_WARN_ON(cpu_buffer,
+                       !local_read(&cpu_buffer->committing)))
+                return;
+
+ again:
+        commits = local_read(&cpu_buffer->commits);
+        /* synchronize with interrupts */
+        barrier();
+        if (local_read(&cpu_buffer->committing) == 1)
+                rb_set_commit_to_write(cpu_buffer);
+
+        local_dec(&cpu_buffer->committing);
+
+        /* synchronize with interrupts */
+        barrier();
+
+        /*
+         * Need to account for interrupts coming in between the
+         * updating of the commit page and the clearing of the
+         * committing counter.
+         */
+        if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
+            !local_read(&cpu_buffer->committing)) {
+                local_inc(&cpu_buffer->committing);
+                goto again;
+        }
+}
+
 static struct ring_buffer_event *
 rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
                       unsigned long length)
@@ -1454,6 +1489,8 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
         int commit = 0;
         int nr_loops = 0;
 
+        rb_start_commit(cpu_buffer);
+
         length = rb_calculate_event_length(length);
  again:
         /*
@@ -1466,7 +1503,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
          * Bail!
          */
         if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
-                return NULL;
+                goto out_fail;
 
         ts = rb_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
 
@@ -1497,7 +1534,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
 
                         commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
                         if (commit == -EBUSY)
-                                return NULL;
+                                goto out_fail;
 
                         if (commit == -EAGAIN)
                                 goto again;
@@ -1511,28 +1548,19 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
         if (unlikely(PTR_ERR(event) == -EAGAIN))
                 goto again;
 
-        if (!event) {
-                if (unlikely(commit))
-                        /*
-                         * Ouch! We needed a timestamp and it was commited. But
-                         * we didn't get our event reserved.
-                         */
-                        rb_set_commit_to_write(cpu_buffer);
-                return NULL;
-        }
+        if (!event)
+                goto out_fail;
 
-        /*
-         * If the timestamp was commited, make the commit our entry
-         * now so that we will update it when needed.
-         */
-        if (unlikely(commit))
-                rb_set_commit_event(cpu_buffer, event);
-        else if (!rb_is_commit(cpu_buffer, event))
+        if (!rb_event_is_commit(cpu_buffer, event))
                 delta = 0;
 
         event->time_delta = delta;
 
         return event;
+
+ out_fail:
+        rb_end_commit(cpu_buffer);
+        return NULL;
 }
 
 #define TRACE_RECURSIVE_DEPTH 16
@@ -1642,13 +1670,14 @@ static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
 {
         local_inc(&cpu_buffer->entries);
 
-        /* Only process further if we own the commit */
-        if (!rb_is_commit(cpu_buffer, event))
-                return;
-
-        cpu_buffer->write_stamp += event->time_delta;
+        /*
+         * The event first in the commit queue updates the
+         * time stamp.
+         */
+        if (rb_event_is_commit(cpu_buffer, event))
+                cpu_buffer->write_stamp += event->time_delta;
 
-        rb_set_commit_to_write(cpu_buffer);
+        rb_end_commit(cpu_buffer);
 }
 
 /**
@@ -1737,15 +1766,15 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
         /* The event is discarded regardless */
         rb_event_discard(event);
 
+        cpu = smp_processor_id();
+        cpu_buffer = buffer->buffers[cpu];
+
         /*
          * This must only be called if the event has not been
          * committed yet. Thus we can assume that preemption
          * is still disabled.
          */
-        RB_WARN_ON(buffer, preemptible());
-
-        cpu = smp_processor_id();
-        cpu_buffer = buffer->buffers[cpu];
+        RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
 
         if (!rb_try_to_discard(cpu_buffer, event))
                 goto out;
@@ -1756,13 +1785,7 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
          */
         local_inc(&cpu_buffer->entries);
  out:
-        /*
-         * If a write came in and pushed the tail page
-         * we still need to update the commit pointer
-         * if we were the commit.
-         */
-        if (rb_is_commit(cpu_buffer, event))
-                rb_set_commit_to_write(cpu_buffer);
+        rb_end_commit(cpu_buffer);
 
         trace_recursive_unlock();
 
@@ -2446,6 +2469,21 @@ 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)
+{
+        /*
+         * 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.
+         */
+        if (likely(!in_nmi() && !oops_in_progress))
+                return 1;
+
+        tracing_off_permanent();
+        return 0;
+}
+
 /**
  * ring_buffer_peek - peek at the next event to be read
  * @buffer: The ring buffer to read
@@ -2461,14 +2499,20 @@ 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;
 
         if (!cpumask_test_cpu(cpu, buffer->cpumask))
                 return NULL;
 
+        dolock = rb_ok_to_lock();
  again:
-        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        local_irq_save(flags);
+        if (dolock)
+                spin_lock(&cpu_buffer->reader_lock);
         event = rb_buffer_peek(buffer, cpu, ts);
-        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+        if (dolock)
+                spin_unlock(&cpu_buffer->reader_lock);
+        local_irq_restore(flags);
 
         if (event && event->type_len == RINGBUF_TYPE_PADDING) {
                 cpu_relax();
@@ -2520,6 +2564,9 @@ 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();
 
  again:
         /* might be called in atomic */
@@ -2529,7 +2576,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
                 goto out;
 
         cpu_buffer = buffer->buffers[cpu];
-        spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+        local_irq_save(flags);
+        if (dolock)
+                spin_lock(&cpu_buffer->reader_lock);
 
         event = rb_buffer_peek(buffer, cpu, ts);
         if (!event)
@@ -2538,7 +2587,9 @@ ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
         rb_advance_reader(cpu_buffer);
 
  out_unlock:
-        spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+        if (dolock)
+                spin_unlock(&cpu_buffer->reader_lock);
+        local_irq_restore(flags);
 
  out:
         preempt_enable();
@@ -2680,6 +2731,8 @@ rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
         cpu_buffer->overrun = 0;
         cpu_buffer->read = 0;
         local_set(&cpu_buffer->entries, 0);
+        local_set(&cpu_buffer->committing, 0);
+        local_set(&cpu_buffer->commits, 0);
 
         cpu_buffer->write_stamp = 0;
         cpu_buffer->read_stamp = 0;
@@ -2734,12 +2787,25 @@ EXPORT_SYMBOL_GPL(ring_buffer_reset);
 int ring_buffer_empty(struct ring_buffer *buffer)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
+        unsigned long flags;
+        int 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];
-                if (!rb_per_cpu_empty(cpu_buffer))
+                local_irq_save(flags);
+                if (dolock)
+                        spin_lock(&cpu_buffer->reader_lock);
+                ret = rb_per_cpu_empty(cpu_buffer);
+                if (dolock)
+                        spin_unlock(&cpu_buffer->reader_lock);
+                local_irq_restore(flags);
+
+                if (!ret)
                         return 0;
         }
 
@@ -2755,14 +2821,23 @@ EXPORT_SYMBOL_GPL(ring_buffer_empty);
 int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
 {
         struct ring_buffer_per_cpu *cpu_buffer;
+        unsigned long flags;
+        int 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)
+                spin_lock(&cpu_buffer->reader_lock);
         ret = rb_per_cpu_empty(cpu_buffer);
-
+        if (dolock)
+                spin_unlock(&cpu_buffer->reader_lock);
+        local_irq_restore(flags);
 
         return ret;
 }
@@ -3108,7 +3183,7 @@ static int rb_cpu_notify(struct notifier_block *self,
         switch (action) {
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
-                if (cpu_isset(cpu, *buffer->cpumask))
+                if (cpumask_test_cpu(cpu, buffer->cpumask))
                         return NOTIFY_OK;
 
                 buffer->buffers[cpu] =
@@ -3119,7 +3194,7 @@ static int rb_cpu_notify(struct notifier_block *self,
                         return NOTIFY_OK;
                 }
                 smp_wmb();
-                cpu_set(cpu, *buffer->cpumask);
+                cpumask_set_cpu(cpu, buffer->cpumask);
                 break;
         case CPU_DOWN_PREPARE:
         case CPU_DOWN_PREPARE_FROZEN:
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 8d68e149a8b3..573d3cc762c3 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -102,8 +102,10 @@ static enum event_status read_page(int cpu)
                         event = (void *)&rpage->data[i];
                         switch (event->type_len) {
                         case RINGBUF_TYPE_PADDING:
-                                /* We don't expect any padding */
-                                KILL_TEST();
+                                /* failed writes may be discarded events */
+                                if (!event->time_delta)
+                                        KILL_TEST();
+                                inc = event->array[0] + 4;
                                 break;
                         case RINGBUF_TYPE_TIME_EXTEND:
                                 inc = 8;
@@ -119,7 +121,7 @@ static enum event_status read_page(int cpu)
                                         KILL_TEST();
                                         break;
                                 }
-                                inc = event->array[0];
+                                inc = event->array[0] + 4;
                                 break;
                         default:
                                 entry = ring_buffer_event_data(event);
@@ -201,7 +203,7 @@ static void ring_buffer_producer(void)
          * Hammer the buffer for 10 secs (this may
          * make the system stall)
          */
-        pr_info("Starting ring buffer hammer\n");
+        trace_printk("Starting ring buffer hammer\n");
         do_gettimeofday(&start_tv);
         do {
                 struct ring_buffer_event *event;
@@ -237,7 +239,7 @@ static void ring_buffer_producer(void)
 #endif
 
         } while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);
-        pr_info("End ring buffer hammer\n");
+        trace_printk("End ring buffer hammer\n");
 
         if (consumer) {
                 /* Init both completions here to avoid races */
@@ -260,49 +262,50 @@ static void ring_buffer_producer(void)
         overruns = ring_buffer_overruns(buffer);
 
         if (kill_test)
-                pr_info("ERROR!\n");
-        pr_info("Time:     %lld (usecs)\n", time);
-        pr_info("Overruns: %lld\n", overruns);
+                trace_printk("ERROR!\n");
+        trace_printk("Time:     %lld (usecs)\n", time);
+        trace_printk("Overruns: %lld\n", overruns);
         if (disable_reader)
-                pr_info("Read:     (reader disabled)\n");
+                trace_printk("Read:     (reader disabled)\n");
         else
-                pr_info("Read:     %ld  (by %s)\n", read,
+                trace_printk("Read:     %ld  (by %s)\n", read,
                         read_events ? "events" : "pages");
-        pr_info("Entries:  %lld\n", entries);
-        pr_info("Total:    %lld\n", entries + overruns + read);
-        pr_info("Missed:   %ld\n", missed);
-        pr_info("Hit:      %ld\n", hit);
+        trace_printk("Entries:  %lld\n", entries);
+        trace_printk("Total:    %lld\n", entries + overruns + read);
+        trace_printk("Missed:   %ld\n", missed);
+        trace_printk("Hit:      %ld\n", hit);
 
         /* Convert time from usecs to millisecs */
         do_div(time, USEC_PER_MSEC);
         if (time)
                 hit /= (long)time;
         else
-                pr_info("TIME IS ZERO??\n");
+                trace_printk("TIME IS ZERO??\n");
 
-        pr_info("Entries per millisec: %ld\n", hit);
+        trace_printk("Entries per millisec: %ld\n", hit);
 
         if (hit) {
                 /* Calculate the average time in nanosecs */
                 avg = NSEC_PER_MSEC / hit;
-                pr_info("%ld ns per entry\n", avg);
+                trace_printk("%ld ns per entry\n", avg);
         }
 
         if (missed) {
                 if (time)
                         missed /= (long)time;
 
-                pr_info("Total iterations per millisec: %ld\n", hit + missed);
+                trace_printk("Total iterations per millisec: %ld\n",
+                             hit + missed);
 
                 /* it is possible that hit + missed will overflow and be zero */
                 if (!(hit + missed)) {
-                        pr_info("hit + missed overflowed and totalled zero!\n");
+                        trace_printk("hit + missed overflowed and totalled zero!\n");
                         hit--; /* make it non zero */
                 }
 
                 /* Caculate the average time in nanosecs */
                 avg = NSEC_PER_MSEC / (hit + missed);
-                pr_info("%ld ns per entry\n", avg);
+                trace_printk("%ld ns per entry\n", avg);
         }
 }
 
@@ -353,7 +356,7 @@ static int ring_buffer_producer_thread(void *arg)
 
                 ring_buffer_producer();
 
-                pr_info("Sleeping for 10 secs\n");
+                trace_printk("Sleeping for 10 secs\n");
                 set_current_state(TASK_INTERRUPTIBLE);
                 schedule_timeout(HZ * SLEEP_TIME);
                 __set_current_state(TASK_RUNNING);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c1878bfb2e1e..076fa6f0ee48 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2191,11 +2191,12 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
         if (!alloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
                 return -ENOMEM;
 
-        mutex_lock(&tracing_cpumask_update_lock);
         err = cpumask_parse_user(ubuf, count, tracing_cpumask_new);
         if (err)
                 goto err_unlock;
 
+        mutex_lock(&tracing_cpumask_update_lock);
+
         local_irq_disable();
         __raw_spin_lock(&ftrace_max_lock);
         for_each_tracing_cpu(cpu) {
@@ -2223,8 +2224,7 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
         return count;
 
 err_unlock:
-        mutex_unlock(&tracing_cpumask_update_lock);
-        free_cpumask_var(tracing_cpumask);
+        free_cpumask_var(tracing_cpumask_new);
 
         return err;
 }
@@ -3626,7 +3626,7 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
         struct trace_seq *s;
         unsigned long cnt;
 
-        s = kmalloc(sizeof(*s), GFP_ATOMIC);
+        s = kmalloc(sizeof(*s), GFP_KERNEL);
         if (!s)
                 return ENOMEM;
 
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index db6e54bdb596..936c621bbf46 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -27,8 +27,6 @@
 #include "trace.h"
 #include "trace_output.h"
 
-static DEFINE_MUTEX(filter_mutex);
-
 enum filter_op_ids
 {
         OP_OR,
@@ -178,7 +176,7 @@ static int filter_pred_string(struct filter_pred *pred, void *event,
 static int filter_pred_strloc(struct filter_pred *pred, void *event,
                               int val1, int val2)
 {
-        int str_loc = *(int *)(event + pred->offset);
+        unsigned short str_loc = *(unsigned short *)(event + pred->offset);
         char *addr = (char *)(event + str_loc);
         int cmp, match;
 
@@ -294,12 +292,12 @@ void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s)
 {
         struct event_filter *filter = call->filter;
 
-        mutex_lock(&filter_mutex);
+        mutex_lock(&event_mutex);
         if (filter->filter_string)
                 trace_seq_printf(s, "%s\n", filter->filter_string);
         else
                 trace_seq_printf(s, "none\n");
-        mutex_unlock(&filter_mutex);
+        mutex_unlock(&event_mutex);
 }
 
 void print_subsystem_event_filter(struct event_subsystem *system,
@@ -307,12 +305,12 @@ void print_subsystem_event_filter(struct event_subsystem *system,
 {
         struct event_filter *filter = system->filter;
 
-        mutex_lock(&filter_mutex);
+        mutex_lock(&event_mutex);
         if (filter->filter_string)
                 trace_seq_printf(s, "%s\n", filter->filter_string);
         else
                 trace_seq_printf(s, "none\n");
-        mutex_unlock(&filter_mutex);
+        mutex_unlock(&event_mutex);
 }
 
 static struct ftrace_event_field *
@@ -381,6 +379,7 @@ void destroy_preds(struct ftrace_event_call *call)
                         filter_free_pred(filter->preds[i]);
         }
         kfree(filter->preds);
+        kfree(filter->filter_string);
         kfree(filter);
         call->filter = NULL;
 }
@@ -433,7 +432,6 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
                 filter->n_preds = 0;
         }
 
-        mutex_lock(&event_mutex);
         list_for_each_entry(call, &ftrace_events, list) {
                 if (!call->define_fields)
                         continue;
@@ -443,7 +441,6 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
                         remove_filter_string(call->filter);
                 }
         }
-        mutex_unlock(&event_mutex);
 }
 
 static int filter_add_pred_fn(struct filter_parse_state *ps,
@@ -546,6 +543,7 @@ static int filter_add_pred(struct filter_parse_state *ps,
         filter_pred_fn_t fn;
         unsigned long long val;
         int string_type;
+        int ret;
 
         pred->fn = filter_pred_none;
 
@@ -581,7 +579,11 @@ static int filter_add_pred(struct filter_parse_state *ps,
                         pred->not = 1;
                 return filter_add_pred_fn(ps, call, pred, fn);
         } else {
-                if (strict_strtoull(pred->str_val, 0, &val)) {
+                if (field->is_signed)
+                        ret = strict_strtoll(pred->str_val, 0, &val);
+                else
+                        ret = strict_strtoull(pred->str_val, 0, &val);
+                if (ret) {
                         parse_error(ps, FILT_ERR_ILLEGAL_INTVAL, 0);
                         return -EINVAL;
                 }
@@ -625,7 +627,6 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
         filter->preds[filter->n_preds] = pred;
         filter->n_preds++;
 
-        mutex_lock(&event_mutex);
         list_for_each_entry(call, &ftrace_events, list) {
 
                 if (!call->define_fields)
@@ -636,14 +637,12 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
 
                 err = filter_add_pred(ps, call, pred);
                 if (err) {
-                        mutex_unlock(&event_mutex);
                         filter_free_subsystem_preds(system);
                         parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
                         goto out;
                 }
                 replace_filter_string(call->filter, filter_string);
         }
-        mutex_unlock(&event_mutex);
 out:
         return err;
 }
@@ -1070,12 +1069,12 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
 
         struct filter_parse_state *ps;
 
-        mutex_lock(&filter_mutex);
+        mutex_lock(&event_mutex);
 
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_disable_preds(call);
                 remove_filter_string(call->filter);
-                mutex_unlock(&filter_mutex);
+                mutex_unlock(&event_mutex);
                 return 0;
         }
 
@@ -1103,7 +1102,7 @@ out:
         postfix_clear(ps);
         kfree(ps);
 out_unlock:
-        mutex_unlock(&filter_mutex);
+        mutex_unlock(&event_mutex);
 
         return err;
 }
@@ -1115,12 +1114,12 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
 
         struct filter_parse_state *ps;
 
-        mutex_lock(&filter_mutex);
+        mutex_lock(&event_mutex);
 
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_free_subsystem_preds(system);
                 remove_filter_string(system->filter);
-                mutex_unlock(&filter_mutex);
+                mutex_unlock(&event_mutex);
                 return 0;
         }
 
@@ -1148,7 +1147,7 @@ out:
         postfix_clear(ps);
         kfree(ps);
 out_unlock:
-        mutex_unlock(&filter_mutex);
+        mutex_unlock(&event_mutex);
 
         return err;
 }
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index c9a0b7df44ff..90f134764837 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -193,9 +193,11 @@ static void tracing_start_function_trace(void)
 static void tracing_stop_function_trace(void)
 {
         ftrace_function_enabled = 0;
-        /* OK if they are not registered */
-        unregister_ftrace_function(&trace_stack_ops);
-        unregister_ftrace_function(&trace_ops);
+
+        if (func_flags.val & TRACE_FUNC_OPT_STACK)
+                unregister_ftrace_function(&trace_stack_ops);
+        else
+                unregister_ftrace_function(&trace_ops);
 }
 
 static int func_set_flag(u32 old_flags, u32 bit, int set)
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 8b592418d8b2..d2249abafb53 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -57,7 +57,8 @@ static struct tracer_flags tracer_flags = {
 
 /* Add a function return address to the trace stack on thread info.*/
 int
-ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
+ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
+                         unsigned long frame_pointer)
 {
         unsigned long long calltime;
         int index;
@@ -85,6 +86,7 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
         current->ret_stack[index].func = func;
         current->ret_stack[index].calltime = calltime;
         current->ret_stack[index].subtime = 0;
+        current->ret_stack[index].fp = frame_pointer;
         *depth = index;
 
         return 0;
@@ -92,7 +94,8 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
 
 /* Retrieve a function return address to the trace stack on thread info.*/
 static void
-ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
+ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
+                        unsigned long frame_pointer)
 {
         int index;
 
@@ -106,6 +109,31 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
                 return;
         }
 
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+        /*
+         * The arch may choose to record the frame pointer used
+         * and check it here to make sure that it is what we expect it
+         * to be. If gcc does not set the place holder of the return
+         * address in the frame pointer, and does a copy instead, then
+         * the function graph trace will fail. This test detects this
+         * case.
+         *
+         * Currently, x86_32 with optimize for size (-Os) makes the latest
+         * gcc do the above.
+         */
+        if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
+                ftrace_graph_stop();
+                WARN(1, "Bad frame pointer: expected %lx, received %lx\n"
+                     "  from func %pF return to %lx\n",
+                     current->ret_stack[index].fp,
+                     frame_pointer,
+                     (void *)current->ret_stack[index].func,
+                     current->ret_stack[index].ret);
+                *ret = (unsigned long)panic;
+                return;
+        }
+#endif
+
         *ret = current->ret_stack[index].ret;
         trace->func = current->ret_stack[index].func;
         trace->calltime = current->ret_stack[index].calltime;
@@ -117,12 +145,12 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
  * Send the trace to the ring-buffer.
  * @return the original return address.
  */
-unsigned long ftrace_return_to_handler(void)
+unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 {
         struct ftrace_graph_ret trace;
         unsigned long ret;
 
-        ftrace_pop_return_trace(&trace, &ret);
+        ftrace_pop_return_trace(&trace, &ret, frame_pointer);
         trace.rettime = trace_clock_local();
         ftrace_graph_return(&trace);
         barrier();
diff --git a/samples/trace_events/Makefile b/samples/trace_events/Makefile
index 0d428dc67283..0f8d92120c4e 100644
--- a/samples/trace_events/Makefile
+++ b/samples/trace_events/Makefile
@@ -1,6 +1,14 @@
 # builds the trace events example kernel modules;
 # then to use one (as root):  insmod <module_name.ko>
 
+# If you include a trace header outside of include/trace/events
+# then the file that does the #define CREATE_TRACE_POINTS must
+# have that tracer file in its main search path. This is because
+# define_trace.h will include it, and must be able to find it from
+# the include/trace directory.
+#
+# Here trace-events-sample.c does the CREATE_TRACE_POINTS.
+#
 CFLAGS_trace-events-sample.o := -I$(src)
 
 obj-$(CONFIG_SAMPLE_TRACE_EVENTS) += trace-events-sample.o
diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index 128a897687c5..9977a756fb32 100644
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -19,16 +19,21 @@
  * If TRACE_SYSTEM is defined, that will be the directory created
  * in the ftrace directory under /debugfs/tracing/events/<system>
  *
- * The define_trace.h belowe will also look for a file name of
+ * The define_trace.h below will also look for a file name of
  * TRACE_SYSTEM.h where TRACE_SYSTEM is what is defined here.
+ * In this case, it would look for sample.h
  *
- * If you want a different system than file name, you can override
- * the header name by defining TRACE_INCLUDE_FILE
+ * If the header name will be different than the system name
+ * (as in this case), then you can override the header name that
+ * define_trace.h will look up by defining TRACE_INCLUDE_FILE
  *
- * If this file was called, goofy.h, then we would define:
+ * This file is called trace-events-sample.h but we want the system
+ * to be called "sample". Therefore we must define the name of this
+ * file:
  *
- * #define TRACE_INCLUDE_FILE goofy
+ * #define TRACE_INCLUDE_FILE trace-events-sample
  *
+ * As we do an the bottom of this file.
  */
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM sample
@@ -99,13 +104,13 @@ TRACE_EVENT(foo_bar,
  *
  * #define TRACE_INCLUDE_PATH ../../samples/trace_events
  *
- * But I chose to simply make it use the current directory and then in
- * the Makefile I added:
+ * But the safest and easiest way to simply make it use the directory
+ * that the file is in is to add in the Makefile:
  *
- * CFLAGS_trace-events-sample.o := -I$(PWD)/samples/trace_events/
+ * CFLAGS_trace-events-sample.o := -I$(src)
  *
  * This will make sure the current path is part of the include
- * structure for our file so that we can find it.
+ * structure for our file so that define_trace.h can find it.
  *
  * I could have made only the top level directory the include:
  *
@@ -115,8 +120,8 @@ TRACE_EVENT(foo_bar,
  *
  * #define TRACE_INCLUDE_PATH samples/trace_events
  *
- * But then if something defines "samples" or "trace_events" then we
- * could risk that being converted too, and give us an unexpected
+ * But then if something defines "samples" or "trace_events" as a macro
+ * then we could risk that being converted too, and give us an unexpected
  * result.
  */
 #undef TRACE_INCLUDE_PATH