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Commit 30379440 authored by Gerald Britton's avatar Gerald Britton Committed by Linus Torvalds
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[PATCH] x86: fix oprofile kernel callgraph regression 



Fix x86 oprofile regression introduced by:
  commit c34d1b4d
  [PATCH] mm: kill check_user_page_readable

That commit reorganized tests for the userspace stack walking moving all
those tests into dump_backtrace(), however, dump_backtrace() was used for
both userspace and kernel stalk walking.  The result is typically no
recorded callgraph information for kernel samples.

Revive the original function as dump_kernel_backtrace() and rename the
other to dump_user_backtrace() to avoid future confusion.

Signed-off-by: default avatarGerald Britton <gbritton@alum.mit.edu>
Apology-from: Hugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b739db79

arch/i386/oprofile/backtrace.c

+16 −3
Original line number Diff line number Diff line
@@ -20,7 +20,20 @@ struct frame_head { 
} __attribute__((packed));



static struct frame_head *

dump_backtrace(struct frame_head * head)

dump_kernel_backtrace(struct frame_head * head)

{

	oprofile_add_trace(head->ret);



	/* frame pointers should strictly progress back up the stack

	 * (towards higher addresses) */

	if (head >= head->ebp)

		return NULL;



	return head->ebp;

}



static struct frame_head *

dump_user_backtrace(struct frame_head * head)

{

	struct frame_head bufhead[2];
@@ -105,10 +118,10 @@ x86_backtrace(struct pt_regs * const regs, unsigned int depth) 


	if (!user_mode_vm(regs)) {

		while (depth-- && valid_kernel_stack(head, regs))

			head = dump_backtrace(head);

			head = dump_kernel_backtrace(head);

		return;

	}



	while (depth-- && head)

		head = dump_backtrace(head);

		head = dump_user_backtrace(head);

}