x86/irq, context_tracking: Document how IRQ context tracking works and add an RCU assertion
x86/irq, context_tracking: Document how IRQ context tracking works and add an RCU assertion

Signed-off-by: Andy Lutomirski <2cc0d0d76de2e6f37b92deeb83c85cb306fc5dc1@kernel.org>
Cc: Andy Lutomirski <2cc0d0d76de2e6f37b92deeb83c85cb306fc5dc1@amacapital.net>
Cc: Borislav Petkov <0691a664b24b6f15b20cd5aee64b72271db08be1@alien8.de>
Cc: Brian Gerst <e60badcb99f652a0bcc15460d39f7ea12d6655ee@gmail.com>
Cc: Denys Vlasenko <50fbbd36fe0f9c8261d4a3c762c8c29ffb35e48f@redhat.com>
Cc: Denys Vlasenko <42afb3a19136e88700e8b77002ea6a5a94c16782@googlemail.com>
Cc: Frederic Weisbecker <e8a1bf9163cb25e93cfd6540f223b3872ea7ee55@gmail.com>
Cc: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>
Cc: Kees Cook <50cb10d2be062154b17ab4d66a4eab34f1cf1c84@chromium.org>
Cc: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Cc: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Cc: Paul E. McKenney <1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Rik van Riel <a21938f5d463ddf41aa718934c205ca2cce8ebbc@redhat.com>
Cc: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>
Cc: 1e0ce936bb9b355d257bf5790d2513c3f28be22b@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/e8bdc4ed0193fb2fd130f3d6b7b8023e2ec1ab62.1435952415.git.2cc0d0d76de2e6f37b92deeb83c85cb306fc5dc1@kernel.org
Signed-off-by: Ingo Molnar <9dbbbf0688fedc85ad4da37637f1a64b8c718ee2@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs