Messages in this thread Patch in this message | | | Date | Wed, 23 Apr 2014 13:56:06 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2/8] printk: Release lockbuf_lock before calling console_trylock_for_printk() |
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On Tue, 25 Mar 2014 18:54:55 +0100 Jan Kara <jack@suse.cz> wrote:
> There's no reason to hold lockbuf_lock when entering > console_trylock_for_printk(). The first thing this function does is > calling down_trylock(console_sem) and if that fails it immediately > unlocks lockbuf_lock. So lockbuf_lock isn't needed for that branch. > When down_trylock() succeeds, the rest of console_trylock() is OK > without lockbuf_lock (it is called without it from other places), and > the only remaining thing in console_trylock_for_printk() is > can_use_console() call. For that call console_sem is enough (it > iterates all consoles and checks CON_ANYTIME flag). > > So we drop logbuf_lock before entering console_trylock_for_printk() > which simplifies the code. >
I suppose we should document have_callable_console()'s locking requirements, and I don't think that "early in boot" part is true?
--- a/kernel/printk/printk.c~printk-release-lockbuf_lock-before-calling-console_trylock_for_printk-fix +++ a/kernel/printk/printk.c @@ -1377,7 +1377,9 @@ static void zap_locks(void) sema_init(&console_sem, 1); } -/* Check if we have any console registered that can be called early in boot. */ +/* + * Check if we have any console registered. Requires console_sem. + */ static int have_callable_console(void) { struct console *con; _
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