On Tuesday 22 February 2005 21:41, Blaisorblade wrote: > On Friday 18 February 2005 16:33, Anton Altaparmakov wrote: > > On Wed, 2005-02-16 at 19:35 +0100, Blaisorblade wrote: > > > On Monday 14 February 2005 12:48, Anton Altaparmakov wrote: > > > > Hi, > > > > > > > > I get a few Debug messages of the form from UML: > > > > > > > > Debug: sleeping function called from invalid context at > > > > include/asm/arch/semaphore.h:107 > > > > in_atomic():0, irqs_disabled():1 > > > > Call Trace: > > > > 087d77b0: [<0809aaa5>] __might_sleep+0x135/0x180 > > > > 087d77d8: [<084d377f>] mcount+0xf/0x20 > > > > 087d77e0: [<0807cc13>] uml_console_write+0x33/0x80 > > > > > > > > Most are coming via uml_console_write. > > > > > > The problem is that the UML tty drivers use a semaphore instead of a > > > spinlock for the locking, which also causes some other problems. > > > > > > The attached patch should fix this, but I've not yet made sure it is > > > not deadlock-prone (I didn't hit any during some very limited testing). > > > > > > So it's not yet ready for 2.6.11. > > > > Trying with the above patch in now only get two "sleeping function > > called from invalid context" warnings during boot and none during > > running. > > I'll look at whether I can produce them... if it's no problem, post their > traces anyway, please. I'm not able... I *did* enable CONFIG_DEBUG_SPINLOCK and CONFIG_DEBUG_SPINLOCK_SLEEP, but still I don't get them.
Maybe I have not an interesting enough test case (or kobject debugging is flooding the dmesg ring buffer, which is doing too). > > However I get a lot of those errors: > > > > arch/um/drivers/line.c:262: spin_lock(arch/um/drivers/line.c:085b5900) > > already locked by arch/um/drivers/line.c/262 > > Ok, I'll be looking into them ASAP (which infortunately means not very > soon, sorry). > At a quick look, I see that line 262 is a "spin_lock" called by > line_write_interrupt. I used spin_lock_irqsave everywhere else... but > actually the interrupt must explicitly disable interrupts (I forgot) so, > the simple answer seems to be using spin_lock_irqsave() would fix it. I've done this in the patch I'm working on. I've various stuff on the press, however it should go in for 2.6.12-rc1, I hope. > I > cannot make a patch now. > > > Also both before and after the patch I see a lot of messages like: > > > > kernel: line_write_room: tty2: no room left in buffer > I've never seen them... Ok, correction, I've seen a lot of these... > Anyway, I'm not sure this is a needed warning: > > in include/linux/tty_driver.h, the .write_room member must tell the > available space... it's reasonable that the TTY layer will call a > flush_buffers function. However, looking at stdio_console, I'm seeing that, > in fact, there is no flush_chars function(!!). I'll provide one ASAP. I've not yet removed the warning in the patch, just to be a bit too careful. I'm providing a flush_chars and flush_buffers method. That said, there must be something else going on... it is easy to get the "repeated chars" problem (cat a file is enough), which I thought linked to this: it's when some data is printed and re-printed many times... , and everybody started noticing it just around 2.6.9 / 2.6.10. I'm not sure, but maybe something else is causing the problem... I'm going to work on the ring-buffer handling too, so that I make sure the unusual code paths are also correct (which code paths are usual and which are unusual could have changed). -- Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729 http://www.user-mode-linux.org/~blaisorblade - 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/
