linux-kernel - [PATCH][GIT PULL] ring-buffer: only warn on wrap if buffer is bigger than two pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.00.0904210954090.10097@gandalf.stny.rr.com>
Date:	Tue, 21 Apr 2009 09:55:40 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH][GIT PULL] ring-buffer: only warn on wrap if buffer is bigger
 than two pages


Ingo,

Please pull the latest tip/tracing/ftrace tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
tip/tracing/ftrace


Steven Rostedt (1):
      ring-buffer: only warn on wrap if buffer is bigger than two pages

----
 kernel/trace/ring_buffer.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---------------------------
commit b76929b6d87e98e49a0988b863debb1a12bcf42b
Author: Steven Rostedt <srostedt@...hat.com>
Date:   Tue Apr 21 09:41:26 2009 -0400

    ring-buffer: only warn on wrap if buffer is bigger than two pages
    
    On boot up, to save memory, ftrace allocates the minimum buffer
    which is two pages. Ftrace also goes through a series of tests
    (when configured) on boot up. These tests can fill up a page within
    a single interrupt.
    
    The ring buffer also has a WARN_ON when it detects that the buffer was
    completely filled within a single commit (other commits are allowed to
    be nested).
    
    Combine the small buffer on start up, with the tests that can fill more
    than a single page within an interrupt, this can trigger the WARN_ON.
    
    This patch makes the WARN_ON only happen when the ring buffer consists
    of more than two pages.
    
    [ Impact: prevent false WARN_ON in ftrace startup tests ]
    
    Reported-by: Ingo Molnar <mingo@...e.hu>
    LKML-Reference: <20090421094616.GA14561@...e.hu>
    Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7bcfd3e..61dbdf2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1241,7 +1241,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
 		 * about it.
 		 */
 		if (unlikely(next_page == commit_page)) {
-			WARN_ON_ONCE(1);
+			/* This can easily happen on small ring buffers */
+			WARN_ON_ONCE(buffer->pages > 2);
 			goto out_reset;
 		}
 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/