As can be reproduced easily:

(setq unread-command-events 1) -- emacs now at 100% CPU
(setq unread-command-events nil) -- emacs OK again


In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.10.8)
 of 2015-12-11 on eyal-XPS13-9333
Windowing system distributor `The X.Org Foundation', version 11.0.11501000
System Description: Linux Mint 17.3 Rosa

Configured using:
 `configure --prefix=/usr/local'

Important settings:
  value of $LC_MONETARY: en_US.UTF-8
  value of $LC_NUMERIC: en_US.UTF-8
  value of $LC_TIME: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Emacs-Lisp

Minor modes in effect:
  column-enforce-mode: t
  global-auto-revert-mode: t
  delete-selection-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  better-registers: t
  show-paren-mode: t
  ido-everywhere: t
  global-git-gutter+-mode: t
  git-gutter+-mode: t
  diff-auto-refine-mode: t
  global-git-commit-mode: t
  shell-dirtrack-mode: t
  helm-autoresize-mode: t
  global-eclim-mode: t
  recentf-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Grep finished (matches found) [2 times]
scroll-up-command: End of buffer [9 times]
Mark set
Mark saved where search started [8 times]
Quit [2 times]
user-error: No further undo information
Mark set
scroll-down-one: Beginning of buffer [16 times]
Mark set [2 times]
scroll-up-command: End of buffer

Load-path shadows:
/usr/local/share/emacs/24.5/lisp/emacs-lisp/cl-lib hides
~/.emacs.d/lisp/cl-lib

Features:
(shadow sort mail-extr emacsbug sendmail helm-command helm-elisp
helm-eval edebug eldoc helm-mode hideshow cc-langs misearch
multi-isearch winner image-file key-bindings git-timemachine init
haskell-simple-indent haskell haskell-completions haskell-load
haskell-commands highlight-uses-mode haskell-modules haskell-sandbox
haskell-repl haskell-debug haskell-interactive-mode
haskell-presentation-mode haskell-collapse haskell-navigate-imports
haskell-compile haskell-process haskell-session haskell-cabal
haskell-utils haskell-mode-autoloads smooth-scrolling
column-enforce-mode autorevert filenotify delsel etags-table
auto-install anything woman man grep-a-lot haskell-font-lock
haskell-mode haskell-string haskell-sort-imports haskell-lexeme
haskell-align-imports haskell-compat haskell-complete-module noutline
outline flymake dabbrev haskell-customize haskell-indentation hl-line
keymaps tags-ext undo-tree diff better-registers c-functions os
mode-hooks settings paren grep-all dired-ext indent-region my-custom ido
whitespace cus-start cus-load git-gutter+ magit-blame magit-stash
magit-bisect magit-remote magit-commit magit-sequence magit magit-apply
magit-wip magit-log magit-diff smerge-mode diff-mode magit-core
magit-process magit-popup magit-mode magit-git crm magit-section
magit-utils git-commit log-edit message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 ietf-drums
mailabbrev mail-utils gmm-utils mailheader pcvs-util add-log with-editor
tramp-sh server ctx-switch-face cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs flycheck-via-make
flycheck help-mode subr-x dash hindent helm-proc proced helm-git-grep
helm-ls-git helm-files image-dired tramp tramp-compat tramp-loaddefs
trampver shell pcomplete format-spec dired-x dired-aux ffap helm-buffers
helm-elscreen helm-tags helm-bookmark helm-adaptive helm-info bookmark
pp helm-locate helm-grep helm-regexp helm-plugin helm-external helm-net
browse-url xml url url-proxy url-privacy url-expand url-methods
url-history url-cookie url-domsuf url-util url-parse auth-source
gnus-util mm-util mail-prsvr password-cache url-vars mailcap helm-utils
helm-help helm-types helm helm-source eieio byte-opt bytecomp
byte-compile cl-extra cconv eieio-core helm-multi-match helm-lib dired
vc-git derived grep vc-dir ewoc vc vc-dispatcher helm-config
helm-autoloads helm-easymenu async-bytecomp find-func async eclimd eclim
eclim-problems eclim-maven compile comint ansi-color eclim-ant
eclim-completion eclim-c advice help-fns json eclim-project easy-mmode
edmacro kmacro s ucs-normalize etags ring multiple-cursors-autoloads
package epg-config recentf tree-widget wid-edit cl-macs cl gv
cl-loaddefs cl-lib goto-last-change momentary-display gitattributes-mode
thingatpt easymenu gitignore-mode gitconfig-mode conf-mode rx time-date
tooltip electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
x-win x-dnd tool-bar dnd fontset image regexp-opt fringe tabulated-list
newcomment lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer nadvice loaddefs button faces cus-face macroexp
files text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 610905 39178)
 (symbols 48 43800 3)
 (miscs 40 456 1223)
 (strings 32 106130 7082)
 (string-bytes 1 2986246)
 (vectors 16 58622)
 (vector-slots 8 953242 40103)
 (floats 8 216 552)
 (intervals 56 8293 188)
 (buffers 960 25)
 (heap 1024 55943 3098))


-- 
Eyal