On Wed, 23 Apr 2014 23:44:47 +0200 (CEST) Jiri Kosina <jkos...@suse.cz> wrote:
> On Wed, 23 Apr 2014, Andrew Morton wrote: > > > > > > Echoing values into /proc/sysrq-trigger seems to be a popular way to > > > > > get information out of the kernel. However, dumping information about > > > > > thousands of processes, or hundreds of CPUs to serial console can > > > > > result in IRQs being blocked for minutes, resulting in various kinds > > > > > of cascade failures. > > > > > > > > > > The most common failure is due to interrupts being blocked for a very > > > > > long time. This can lead to things like failed IO requests, and other > > > > > things the system cannot easily recover from. > > > > > > > > I bet nobody wants that console output anyway. You do the sysrq then > > > > run dmesg or look in /var/log/messages to see what happened. People > > > > who are experiencing problems such as this should run `dmesg -n 1' > > > > before writing to sysrq-trigger. > > > > > > I don't agree. I have used sysrq-t multiple times in situations where > > > userspace was already dead, but sysrq was still able to provide valuable > > > information about the state of the kernel. > > > > > > > I'm talking about /proc/sysrq-trigger, not the magic key combo. > > At the end of the day, that reaches the same __handle_sysrq() codepath, > no? What I'm proposing is that we provide a way in which console output may be suppressed during /proc/sysrq-trigger writes. I'm not suggesting that the implementation be buggy ;) But clueful people can run `dmesg -1' beforehand, so I wonder if the patch really has much value? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
