Linus Torvalds 8f4385d590 This code is a fork from the trace-3.19 pull as it needed the trace_seq ... clean ups from that branch. This code solves the issue of performing stack dumps from NMI context. The issue is that printk() is not safe from NMI context as if the NMI were to trigger when a printk() was being performed, the NMI could deadlock from the printk() internal locks. This has been seen in practice. With lots of review from Petr Mladek, this code went through several iterations, and we feel that it is now at a point of quality to be accepted into mainline. Here's what is contained in this patch set: o Creates a "seq_buf" generic buffer utility that allows a descriptor to be passed around where functions can write their own "printk()" formatted strings into it. The generic version was pulled out of the trace_seq() code that was made specifically for tracing. o The seq_buf code was change to model the seq_file code. I have a patch (not included for 3.19) that converts the seq_file.c code over to use seq_buf.c like the trace_seq.c code does. This was done to make sure that seq_buf.c is compatible with seq_file.c. I may try to get that patch in for 3.20. o The seq_buf.c file was moved to lib/ to remove it from being dependent on CONFIG_TRACING. o The printk() was updated to allow for a per_cpu "override" of the internal calls. That is, instead of writing to the console, a call to printk() may do something else. This made it easier to allow the NMI to change what printk() does in order to call dump_stack() without needing to update that code as well. o Finally, the dump_stack from all CPUs via NMI code was converted to use the seq_buf code. The caller to trigger the NMI code would wait till all the NMIs finished, and then it would print the seq_buf data to the console safely from a non NMI context. [ Updated to remove unnecessary preempt_disable in printk() ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAABAgAGBQJUi8A8AAoJEEjnJuOKh9ldv0sH/A+l9Ewrc3Kd0XuUKX9UO9Mj yrDz5dSWTxD6Pi7ni5Zo2f/MebXhrgS8gF1MBN1HMS5s9/9XdTTQijosOfs75iFd xufiDur7ssl2EOLB/ouqWVn16tu1PrPyw+U76JUZvsYlIMSWQu2FH8DSdo59N6Iz 7RxS8rtxJ2IwehmO7tu2Lq5rB7zGL4SET5oIfQ1+KnjzqB5Z1bfm9nGwAc8nozx8 3MqwsClEnXBTkY4eYZzu9wD7Nl/eknzTrk8KDbQ49oTYmoBuuh/s1FMuxe75cY55 wEtDA6HvvTXYnw6YOAMUB41cGnRg3KVRmmhcH5T9jrBxg2iZjXYa8iZxvcAM6Es= =zDMJ -----END PGP SIGNATURE----- Merge tag 'trace-seq-buf-3.19-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fixlet from Steven Rostedt: "Remove unnecessary preempt_disable in printk()" * tag 'trace-seq-buf-3.19-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: printk: Do not disable preemption for accessing printk_func		2014-12-13 14:04:41 -08:00
..
braille.c
braille.h
console_cmdline.h
Makefile
printk.c