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Merge tag 'trace-v4.7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

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Pull motr tracing updates from Steven Rostedt:
 "Three more changes.

   - I forgot that I had another selftest to stress test the ftrace
     instance creation.  It was actually suppose to go into the 4.6
     merge window, but I never committed it.  I almost forgot about it
     again, but noticed it was missing from your tree.

   - Soumya PN sent me a clean up patch to not disable interrupts when
     taking the tasklist_lock for read, as it's unnecessary because that
     lock is never taken for write in irq context.

   - Newer gcc's can cause the jump in the function_graph code to the
     global ftrace_stub label to be a short jump instead of a long one.
     As that jump is dynamically converted to jump to the trace code to
     do function graph tracing, and that conversion expects a long jump
     it can corrupt the ftrace_stub itself (it's directly after that
     call).  One way to prevent gcc from using a short jump is to
     declare the ftrace_stub as a weak function, which we do here to
     keep gcc from optimizing too much"

* tag 'trace-v4.7-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  ftrace/x86: Set ftrace_stub to weak to prevent gcc from using short jumps to it
  ftrace: Don't disable irqs when taking the tasklist_lock read_lock
  ftracetest: Add instance created, delete, read and enable event test
This commit is contained in:
Linus Torvalds
2016-05-22 19:40:39 -07:00
parent 77ed402b7f 8329e818f1
commit 7639dad93a
3 changed files with 147 additions and 4 deletions
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5
kernel/trace/ftrace.c
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@@ -5737,7 +5737,6 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
{
int i;
int ret = 0;
unsigned long flags;
int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
struct task_struct *g, *t;
@@ -5753,7 +5752,7 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
}
}
read_lock_irqsave(&tasklist_lock, flags);
read_lock(&tasklist_lock);
do_each_thread(g, t) {
if (start == end) {
ret = -EAGAIN;
@@ -5771,7 +5770,7 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
} while_each_thread(g, t);
unlock:
read_unlock_irqrestore(&tasklist_lock, flags);
read_unlock(&tasklist_lock);
free:
for (i = start; i < end; i++)
kfree(ret_stack_list[i]);