* Pavel Machek ([EMAIL PROTECTED]) wrote: > Hi! > > > > Hmm, I see this at the beginning of the post-BK era (2.6.12-rc2): > > > > > > spin_lock_irqsave(&logbuf_lock, flags); > > > ... > > > spin_unlock(&logbuf_lock); > > > call_console_drivers(_con_start, _log_end); > > > local_irq_restore(flags); > > > > > > > Well, I need to do some more research. This must be in > > release_console_sem(). I was looking at vprintk, through > > the ages. At 2.6.16, it looked like this: > > > > spin_lock_irqsave(&logbuf_lock, flags); > > ... > > spin_unlock_irqrestore(&logbuf_lock, flags); > > console_may_schedule = 0; > > release_console_sem(); > > > > but the irq restore has been moving around to different places > > in that function over the last few years. I suspect that in the > > common case the irqsave in vprintk is the one that disables > > ints. > > > > It appears that formerly interrupts were enabled in vprintk but > > re-disabled immediately upon entering release_console_sem(). > > As it is now, they're held during formatting, buffering, > > and output, which seems excessive. > > > > It seems draconian to drain the entire buffer with ints disabled. > > Is it possible to break this up and send out smaller chunks > > at a time? Maybe by putting a chunk loop in release_console_sem()? > > Well, I believe someone got > > DDetetccctted ed 113223 HHzz CPUCPU > > in his dmesg, and now we have this 'draconian' locking. How can we > prevent mangled messages without it? > Pavel
The main interest seems to be to protect from mixed printk output between different CPUs in process context. I don't think it would be that bad if interrupts come and output error messages in the middle of a printk, isn't it ? therefore, could we do something like : if (!in_irq()) spin_lock(&logbuf_lock); ... if (!in_irq()) spin_unlock(&logbuf_lock); ? (yes, this is a crazy idea) Mathieu > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) > http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
