On Fri 2018-06-15 17:38:04, Sergey Senozhatsky wrote: > On (06/08/18 10:18), Petr Mladek wrote: > [..] > > > Could be. > > > The good thing about printk_safe is that printk_safe sections can nest. > > > I suspect there might be locks/printk_safe sections nesting at some > > > point. In any case, switching to a new flavor of printk_safe will be > > > pretty easy - just replace printk_safe_enter() with printk_foo_enter() > > > and the same for printk_save_exit(). > > > > We could allow nesting. It is just a matter of how many bits we > > reserve for it in printk_context variable. > [..] > > In each case, I would like to keep the printk_safe context usage > > at minimum. It has its own problems caused by limited per-cpu buffers > > and the need to flush them. > > May be. Every new printk_safe flavour comes with increasing memory > usage. This must be a misunderstanding. My intention was to introduce printk_deferred() context. Where any printk() called in this context would behave like printk_deferred(). It does not need any extra buffers. IMHO, this problem is similar to the problems that we solve in scheduler and timer code. The cure might be the same. I just suggest to introduce a context to make our life easier. > > It is basically needed only to prevent deadlocks related to logbuf_lock. > > I wouldn't say that we need printk_safe for logbuf_lock only. > printk_safe helps us to avoid deadlocks on: > > - logbuf_lock spin_lock logbuf_lock is already guarded by printk_safe context everywhere. > - console_sem ->lock spin_lock > - console_owner spin_lock > - scheduler ->pi_lock spin_lock > - and probably something else. printk_deferred should be enough for others. Or do I miss anything? Best Regards, Petr -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
