linux-kernel - Re: [PATCH printk v1 06/18] printk: nobkl: Add acquire/release logic

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Date:   Mon, 06 Mar 2023 10:45:46 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Dan Carpenter <error27@...il.com>, oe-kbuild@...ts.linux.dev,
        Petr Mladek <pmladek@...e.com>
Cc:     lkp@...el.com, oe-kbuild-all@...ts.linux.dev,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH printk v1 06/18] printk: nobkl: Add acquire/release logic

On 2023-03-06, Dan Carpenter <error27@...il.com> wrote:
> smatch warnings:
> kernel/printk/printk_nobkl.c:391 cons_try_acquire_spin() warn: signedness bug returning '(-16)'

Great catch. That function used to return bool, but recently changed to
int. The consequence of the bug is that a waiter could prematurely abort
the spin.

diff --git a/kernel/printk/printk_nobkl.c b/kernel/printk/printk_nobkl.c
index 78136347a328..bcd75e5bd9c8 100644
--- a/kernel/printk/printk_nobkl.c
+++ b/kernel/printk/printk_nobkl.c
@@ -305,7 +305,7 @@ static bool cons_setup_request(struct cons_context *ctxt, struct cons_state old)
  * handover request setup by cons_setup_handover() is now invalidated and
  * must be performed again).
  */
-static bool cons_try_acquire_spin(struct cons_context *ctxt)
+static int cons_try_acquire_spin(struct cons_context *ctxt)
 {
 	struct console *con = ctxt->console;
 	struct cons_state cur;