diff --git a/.clang-format b/.clang-format
new file mode 100644
index 000000000..7b6c459a3
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,17 @@
+AlwaysBreakAfterDefinitionReturnType: All
+BreakBeforeBinaryOperators: NonAssignment
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterControlStatement: true
+  AfterEnum: true
+  AfterFunction: true
+  AfterStruct: true
+  AfterUnion: true
+  BeforeElse: true
+ColumnLimit: 0
+ContinuationIndentWidth: 2
+IndentCaseLabels: true
+MaxEmptyLinesToKeep: 2
+PointerAlignment: Right
+SpaceAfterCStyleCast: false
+SpacesBeforeTrailingComments: 1
diff --git a/.git-hooks/pre_commit/c_cop.rb b/.git-hooks/pre_commit/c_cop.rb
index 787bb0204..d71dcb236 100644
--- a/.git-hooks/pre_commit/c_cop.rb
+++ b/.git-hooks/pre_commit/c_cop.rb
@@ -17,19 +17,18 @@ def run
 
           offenses = 0
           applicable_files.each do |file|
-            res = execute([required_executable, file, '-o', "#{file}_"])
+            res = execute(command, args: [file])
 
-            unchanged = FileUtils.compare_file(file, "#{file}_") if res.success?
+            unchanged = res.success? && File.read(file) == res.stdout
 
             offenses += 1 unless unchanged
-
-            FileUtils.rm_f("#{file}_")
           end
 
           return :pass if offenses.zero?
 
           file_list = applicable_files.join(' ')
-          [:fail, "#{offenses} errors found. Run `indent #{file_list}`"]
+          fixing_command = "#{command.join(' ')} -i #{file_list}"
+          [:fail, "#{offenses} errors found. Run `#{fixing_command}`"]
         end
       end
     end
diff --git a/.indent.pro b/.indent.pro
deleted file mode 100644
index eae1493eb..000000000
--- a/.indent.pro
+++ /dev/null
@@ -1,27 +0,0 @@
---blank-lines-after-declarations
---blank-lines-after-procedures
---brace-indent 0
---braces-after-if-line
---break-before-boolean-operator
---case-brace-indentation 0
---case-indentation 2
---comment-indentation 1
---continuation-indentation 0
---continue-at-parentheses
---declaration-comment-column 1
---ignore-newlines
---indent-level 2
---leave-optional-blank-lines
---dont-left-justify-declarations
---line-comments-indentation 0
---line-length 80
---no-blank-lines-after-commas
---no-parameter-indentation
---no-space-after-casts
---no-space-after-function-call-names
---no-space-after-parentheses
---no-tabs
---remove-preprocessor-space
---space-after-for
---space-after-if
---space-after-while
diff --git a/.overcommit.yml b/.overcommit.yml
index 97c236fe4..dbf341d90 100644
--- a/.overcommit.yml
+++ b/.overcommit.yml
@@ -23,11 +23,11 @@ CommitMsg:
 #
 PreCommit:
   CCop:
-    description: Analyzing C files with indent
+    description: Formatting C files with clang-format
     enabled: true
-    required_executable: indent
-    install_command: sudo apt-get install indent
+    required_executable: clang-format
     include: ext/byebug/*.[ch]
+    flags: ['-style=file']
 
   BundleCheck:
     enabled: true
diff --git a/.travis.yml b/.travis.yml
index d97794ef9..08cdb9d7c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@ cache:
 language: ruby
 
 before_install:
-  - sudo apt-get install indent shellcheck
+  - sudo apt-get install shellcheck
   - if [ "$LIBEDIT" == "true" ]; then
       sudo apt-get install libedit-dev;
     fi
diff --git a/Dockerfile b/Dockerfile
index 8642399d3..c2a5dbc2f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,6 +7,7 @@ USER root
 RUN apt-get update && apt-get install -y \
   autoconf \
   automake \
+  clang-format \
   bison \
   bzip2 \
   curl \
@@ -14,7 +15,6 @@ RUN apt-get update && apt-get install -y \
   g++ \
   gcc \
   git \
-  indent \
   libc6-dev \
   libffi-dev \
   libgdbm-dev \
diff --git a/ext/byebug/breakpoint.c b/ext/byebug/breakpoint.c
index de07625d6..08e036fa9 100644
--- a/ext/byebug/breakpoint.c
+++ b/ext/byebug/breakpoint.c
@@ -239,7 +239,7 @@ brkpt_source(VALUE self)
 }
 
 static void
-mark_breakpoint(breakpoint_t * breakpoint)
+mark_breakpoint(breakpoint_t *breakpoint)
 {
   rb_gc_mark(breakpoint->source);
   rb_gc_mark(breakpoint->expr);
diff --git a/ext/byebug/byebug.c b/ext/byebug/byebug.c
index 21a097910..d24a81e35 100644
--- a/ext/byebug/byebug.c
+++ b/ext/byebug/byebug.c
@@ -1,6 +1,6 @@
 #include "byebug.h"
 
-static VALUE mByebug;   /* Ruby Byebug Module object */
+static VALUE mByebug; /* Ruby Byebug Module object */
 
 static VALUE tracing = Qfalse;
 static VALUE post_mortem = Qfalse;
@@ -75,7 +75,7 @@ check_started()
 }
 
 static void
-trace_print(rb_trace_arg_t * trace_arg, debug_context_t * dc,
+trace_print(rb_trace_arg_t *trace_arg, debug_context_t *dc,
             const char *file_filter, const char *debug_msg)
 {
   char *fullpath = NULL;
@@ -127,7 +127,7 @@ trace_print(rb_trace_arg_t * trace_arg, debug_context_t * dc,
 }
 
 static void
-cleanup(debug_context_t * dc)
+cleanup(debug_context_t *dc)
 {
   dc->stop_reason = CTX_STOP_NONE;
 
@@ -156,11 +156,11 @@ cleanup(debug_context_t * dc)
   if (CTX_FL_TEST(dc, CTX_FL_IGNORE))                   \
     return;                                             \
                                                         \
-  acquire_lock(dc);                                     \
-                                                        \
+  acquire_lock(dc);
+
 
-#define CALL_EVENT_SETUP                                      \
-  dc->calced_stack_size++;                                    \
+#define CALL_EVENT_SETUP   \
+  dc->calced_stack_size++; \
   dc->steps_out = dc->steps_out < 0 ? -1 : dc->steps_out + 1;
 
 #define RETURN_EVENT_SETUP \
@@ -176,7 +176,7 @@ cleanup(debug_context_t * dc)
 /* Functions that return control to byebug after the different events */
 
 static VALUE
-call_at(VALUE ctx, debug_context_t * dc, ID mid, int argc, VALUE arg)
+call_at(VALUE ctx, debug_context_t *dc, ID mid, int argc, VALUE arg)
 {
   struct call_with_inspection_data cwi;
   VALUE argv[1];
@@ -193,19 +193,19 @@ call_at(VALUE ctx, debug_context_t * dc, ID mid, int argc, VALUE arg)
 }
 
 static VALUE
-call_at_line(VALUE ctx, debug_context_t * dc)
+call_at_line(VALUE ctx, debug_context_t *dc)
 {
   return call_at(ctx, dc, rb_intern("at_line"), 0, Qnil);
 }
 
 static VALUE
-call_at_tracing(VALUE ctx, debug_context_t * dc)
+call_at_tracing(VALUE ctx, debug_context_t *dc)
 {
   return call_at(ctx, dc, rb_intern("at_tracing"), 0, Qnil);
 }
 
 static VALUE
-call_at_breakpoint(VALUE ctx, debug_context_t * dc, VALUE breakpoint)
+call_at_breakpoint(VALUE ctx, debug_context_t *dc, VALUE breakpoint)
 {
   dc->stop_reason = CTX_STOP_BREAKPOINT;
 
@@ -213,7 +213,7 @@ call_at_breakpoint(VALUE ctx, debug_context_t * dc, VALUE breakpoint)
 }
 
 static VALUE
-call_at_catchpoint(VALUE ctx, debug_context_t * dc, VALUE exp)
+call_at_catchpoint(VALUE ctx, debug_context_t *dc, VALUE exp)
 {
   dc->stop_reason = CTX_STOP_CATCHPOINT;
 
@@ -221,7 +221,7 @@ call_at_catchpoint(VALUE ctx, debug_context_t * dc, VALUE exp)
 }
 
 static VALUE
-call_at_return(VALUE ctx, debug_context_t * dc, VALUE return_value)
+call_at_return(VALUE ctx, debug_context_t *dc, VALUE return_value)
 {
   dc->stop_reason = CTX_STOP_BREAKPOINT;
 
@@ -229,7 +229,7 @@ call_at_return(VALUE ctx, debug_context_t * dc, VALUE return_value)
 }
 
 static VALUE
-call_at_end(VALUE ctx, debug_context_t * dc)
+call_at_end(VALUE ctx, debug_context_t *dc)
 {
   dc->stop_reason = CTX_STOP_BREAKPOINT;
 
@@ -237,7 +237,7 @@ call_at_end(VALUE ctx, debug_context_t * dc)
 }
 
 static void
-call_at_line_check(VALUE ctx, debug_context_t * dc, VALUE breakpoint)
+call_at_line_check(VALUE ctx, debug_context_t *dc, VALUE breakpoint)
 {
   dc->stop_reason = CTX_STOP_STEP;
 
@@ -721,7 +721,7 @@ Start(VALUE self)
  *  +stop+ parameter forces byebug to stop at the first line of code in +file+
  */
 static VALUE
-Debug_load(int argc, VALUE * argv, VALUE self)
+Debug_load(int argc, VALUE *argv, VALUE self)
 {
   VALUE file, stop, context;
   debug_context_t *dc;
diff --git a/ext/byebug/byebug.h b/ext/byebug/byebug.h
index de60c7e00..d596b1371 100644
--- a/ext/byebug/byebug.h
+++ b/ext/byebug/byebug.h
@@ -8,22 +8,29 @@
 #define UNUSED(x) (void)(x)
 
 /* flags */
-#define CTX_FL_DEAD         (1<<1)      /* this context belonged to a dead thread */
-#define CTX_FL_IGNORE       (1<<2)      /* this context belongs to ignored thread */
-#define CTX_FL_SUSPEND      (1<<3)      /* thread currently suspended             */
-#define CTX_FL_TRACING      (1<<4)      /* call at_tracing method                 */
-#define CTX_FL_WAS_RUNNING  (1<<5)      /* thread was previously running          */
-#define CTX_FL_STOP_ON_RET  (1<<6)      /* can stop on method 'end'               */
-#define CTX_FL_IGNORE_STEPS (1<<7)      /* doesn't countdown steps to break       */
+#define CTX_FL_DEAD (1 << 1)         /* this context belonged to a dead thread */
+#define CTX_FL_IGNORE (1 << 2)       /* this context belongs to ignored thread */
+#define CTX_FL_SUSPEND (1 << 3)      /* thread currently suspended             */
+#define CTX_FL_TRACING (1 << 4)      /* call at_tracing method                 */
+#define CTX_FL_WAS_RUNNING (1 << 5)  /* thread was previously running          */
+#define CTX_FL_STOP_ON_RET (1 << 6)  /* can stop on method 'end'               */
+#define CTX_FL_IGNORE_STEPS (1 << 7) /* doesn't countdown steps to break       */
 
 /* macro functions */
-#define CTX_FL_TEST(c,f) ((c)->flags & (f))
-#define CTX_FL_SET(c,f) do { (c)->flags |= (f); } while (0)
-#define CTX_FL_UNSET(c,f) do { (c)->flags &= ~(f); } while (0)
+#define CTX_FL_TEST(c, f) ((c)->flags & (f))
+#define CTX_FL_SET(c, f) \
+  do                     \
+  {                      \
+    (c)->flags |= (f);   \
+  } while (0)
+#define CTX_FL_UNSET(c, f) \
+  do                       \
+  {                        \
+    (c)->flags &= ~(f);    \
+  } while (0)
 
 /* types */
-typedef enum
-{
+typedef enum {
   CTX_STOP_NONE,
   CTX_STOP_STEP,
   CTX_STOP_BREAKPOINT,
@@ -39,16 +46,15 @@ typedef struct
   VALUE thread;
   int thnum;
 
-  int dest_frame;       /* next stop's frame if stopped by next     */
-  int lines;    /* # of lines in dest_frame before stopping */
-  int steps;    /* # of steps before stopping               */
-  int steps_out;        /* # of returns before stopping             */
+  int dest_frame; /* next stop's frame if stopped by next     */
+  int lines;      /* # of lines in dest_frame before stopping */
+  int steps;      /* # of steps before stopping               */
+  int steps_out;  /* # of returns before stopping             */
 
-  VALUE backtrace;      /* [[loc, self, klass, binding], ...] */
+  VALUE backtrace; /* [[loc, self, klass, binding], ...] */
 } debug_context_t;
 
-typedef enum
-{
+typedef enum {
   LOCATION,
   SELF,
   CLASS,
@@ -70,10 +76,18 @@ typedef struct
 } threads_table_t;
 
 enum bp_type
-{ BP_POS_TYPE, BP_METHOD_TYPE };
+{
+  BP_POS_TYPE,
+  BP_METHOD_TYPE
+};
 
 enum hit_condition
-{ HIT_COND_NONE, HIT_COND_GE, HIT_COND_EQ, HIT_COND_MOD };
+{
+  HIT_COND_NONE,
+  HIT_COND_GE,
+  HIT_COND_EQ,
+  HIT_COND_MOD
+};
 
 typedef struct
 {
@@ -100,9 +114,9 @@ extern void remove_from_locked(VALUE thread);
 /* functions from threads.c */
 extern void Init_threads_table(VALUE mByebug);
 extern VALUE create_threads_table(void);
-extern void thread_context_lookup(VALUE thread, VALUE * context);
+extern void thread_context_lookup(VALUE thread, VALUE *context);
 extern int is_living_thread(VALUE thread);
-extern void acquire_lock(debug_context_t * dc);
+extern void acquire_lock(debug_context_t *dc);
 extern void release_lock(void);
 
 /* global variables */
@@ -112,10 +126,10 @@ extern VALUE next_thread;
 /* functions from context.c */
 extern void Init_context(VALUE mByebug);
 extern VALUE context_create(VALUE thread);
-extern VALUE context_dup(debug_context_t * context);
-extern void reset_stepping_stop_points(debug_context_t * context);
+extern VALUE context_dup(debug_context_t *context);
+extern void reset_stepping_stop_points(debug_context_t *context);
 extern VALUE call_with_debug_inspector(struct call_with_inspection_data *data);
-extern VALUE context_backtrace_set(const rb_debug_inspector_t * inspector,
+extern VALUE context_backtrace_set(const rb_debug_inspector_t *inspector,
                                    void *data);
 
 /* functions from breakpoint.c */
diff --git a/ext/byebug/context.c b/ext/byebug/context.c
index 7bd2099cb..a9fe0ec7b 100644
--- a/ext/byebug/context.c
+++ b/ext/byebug/context.c
@@ -7,7 +7,7 @@ static int thnum_max = 0;
 /* "Step", "Next" and "Finish" do their work by saving information about where
  * to stop next. reset_stepping_stop_points removes/resets this information. */
 extern void
-reset_stepping_stop_points(debug_context_t * context)
+reset_stepping_stop_points(debug_context_t *context)
 {
   context->dest_frame = -1;
   context->lines = -1;
@@ -34,19 +34,19 @@ Context_dead(VALUE self)
 static void
 context_mark(void *data)
 {
-  debug_context_t *context = (debug_context_t *) data;
+  debug_context_t *context = (debug_context_t *)data;
 
   rb_gc_mark(context->backtrace);
 }
 
 static VALUE
-dc_backtrace(const debug_context_t * context)
+dc_backtrace(const debug_context_t *context)
 {
   return context->backtrace;
 }
 
 static int
-dc_stack_size(debug_context_t * context)
+dc_stack_size(debug_context_t *context)
 {
 
   if (NIL_P(dc_backtrace(context)))
@@ -76,7 +76,7 @@ context_create(VALUE thread)
 }
 
 extern VALUE
-context_dup(debug_context_t * context)
+context_dup(debug_context_t *context)
 {
   debug_context_t *new_context = ALLOC(debug_context_t);
 
@@ -90,7 +90,7 @@ context_dup(debug_context_t * context)
 
 
 static VALUE
-dc_frame_get(const debug_context_t * context, int frame_index, frame_part type)
+dc_frame_get(const debug_context_t *context, int frame_index, frame_part type)
 {
   VALUE frame;
 
@@ -105,31 +105,31 @@ dc_frame_get(const debug_context_t * context, int frame_index, frame_part type)
 }
 
 static VALUE
-dc_frame_location(const debug_context_t * context, int frame_index)
+dc_frame_location(const debug_context_t *context, int frame_index)
 {
   return dc_frame_get(context, frame_index, LOCATION);
 }
 
 static VALUE
-dc_frame_self(const debug_context_t * context, int frame_index)
+dc_frame_self(const debug_context_t *context, int frame_index)
 {
   return dc_frame_get(context, frame_index, SELF);
 }
 
 static VALUE
-dc_frame_class(const debug_context_t * context, int frame_index)
+dc_frame_class(const debug_context_t *context, int frame_index)
 {
   return dc_frame_get(context, frame_index, CLASS);
 }
 
 static VALUE
-dc_frame_binding(const debug_context_t * context, int frame_index)
+dc_frame_binding(const debug_context_t *context, int frame_index)
 {
   return dc_frame_get(context, frame_index, BINDING);
 }
 
 static VALUE
-load_backtrace(const rb_debug_inspector_t * inspector)
+load_backtrace(const rb_debug_inspector_t *inspector)
 {
   VALUE backtrace = rb_ary_new();
   VALUE locs = rb_debug_inspector_backtrace_locations(inspector);
@@ -151,9 +151,9 @@ load_backtrace(const rb_debug_inspector_t * inspector)
 }
 
 extern VALUE
-context_backtrace_set(const rb_debug_inspector_t * inspector, void *data)
+context_backtrace_set(const rb_debug_inspector_t *inspector, void *data)
 {
-  debug_context_t *dc = (debug_context_t *) data;
+  debug_context_t *dc = (debug_context_t *)data;
 
   dc->backtrace = load_backtrace(inspector);
 
@@ -161,7 +161,7 @@ context_backtrace_set(const rb_debug_inspector_t * inspector, void *data)
 }
 
 static VALUE
-open_debug_inspector_i(const rb_debug_inspector_t * inspector, void *data)
+open_debug_inspector_i(const rb_debug_inspector_t *inspector, void *data)
 {
   struct call_with_inspection_data *cwi =
     (struct call_with_inspection_data *)data;
@@ -187,8 +187,8 @@ close_debug_inspector(struct call_with_inspection_data *cwi)
 extern VALUE
 call_with_debug_inspector(struct call_with_inspection_data *data)
 {
-  return rb_ensure(open_debug_inspector, (VALUE) data, close_debug_inspector,
-                   (VALUE) data);
+  return rb_ensure(open_debug_inspector, (VALUE)data, close_debug_inspector,
+                   (VALUE)data);
 }
 
 #define FRAME_SETUP                                \
@@ -208,7 +208,7 @@ call_with_debug_inspector(struct call_with_inspection_data *data)
  *  Returns frame's binding.
  */
 static VALUE
-Context_frame_binding(int argc, VALUE * argv, VALUE self)
+Context_frame_binding(int argc, VALUE *argv, VALUE self)
 {
   FRAME_SETUP;
 
@@ -222,7 +222,7 @@ Context_frame_binding(int argc, VALUE * argv, VALUE self)
  *  Returns frame's defined class.
  */
 static VALUE
-Context_frame_class(int argc, VALUE * argv, VALUE self)
+Context_frame_class(int argc, VALUE *argv, VALUE self)
 {
   FRAME_SETUP;
 
@@ -236,7 +236,7 @@ Context_frame_class(int argc, VALUE * argv, VALUE self)
  *  Returns the name of the file in the frame.
  */
 static VALUE
-Context_frame_file(int argc, VALUE * argv, VALUE self)
+Context_frame_file(int argc, VALUE *argv, VALUE self)
 {
   VALUE loc, absolute_path;
 
@@ -259,7 +259,7 @@ Context_frame_file(int argc, VALUE * argv, VALUE self)
  *  Returns the line number in the file in the frame.
  */
 static VALUE
-Context_frame_line(int argc, VALUE * argv, VALUE self)
+Context_frame_line(int argc, VALUE *argv, VALUE self)
 {
   VALUE loc;
 
@@ -277,7 +277,7 @@ Context_frame_line(int argc, VALUE * argv, VALUE self)
  *  Returns the sym of the method in the frame.
  */
 static VALUE
-Context_frame_method(int argc, VALUE * argv, VALUE self)
+Context_frame_method(int argc, VALUE *argv, VALUE self)
 {
   VALUE loc;
 
@@ -295,7 +295,7 @@ Context_frame_method(int argc, VALUE * argv, VALUE self)
  *  Returns self object of the frame.
  */
 static VALUE
-Context_frame_self(int argc, VALUE * argv, VALUE self)
+Context_frame_self(int argc, VALUE *argv, VALUE self)
 {
   FRAME_SETUP;
 
@@ -395,7 +395,7 @@ Context_stop_reason(VALUE self)
  *  +frame+ (by default the newest one).
  */
 static VALUE
-Context_step_into(int argc, VALUE * argv, VALUE self)
+Context_step_into(int argc, VALUE *argv, VALUE self)
 {
   VALUE steps, v_frame;
   int n_args, from_frame;
@@ -435,7 +435,7 @@ Context_step_into(int argc, VALUE * argv, VALUE self)
  *  event for that frame is triggered.
  */
 static VALUE
-Context_step_out(int argc, VALUE * argv, VALUE self)
+Context_step_out(int argc, VALUE *argv, VALUE self)
 {
   int n_args, n_frames;
   VALUE v_frames, force;
@@ -468,7 +468,7 @@ Context_step_out(int argc, VALUE * argv, VALUE self)
  *  higher (if frame +frame+ finishes).
  */
 static VALUE
-Context_step_over(int argc, VALUE * argv, VALUE self)
+Context_step_over(int argc, VALUE *argv, VALUE self)
 {
   int n_args, frame;
   VALUE lines, v_frame;
diff --git a/ext/byebug/threads.c b/ext/byebug/threads.c
index 5ea719c85..1a656e1c5 100644
--- a/ext/byebug/threads.c
+++ b/ext/byebug/threads.c
@@ -14,12 +14,12 @@ t_tbl_mark_keyvalue(st_data_t key, st_data_t value, st_data_t tbl)
 {
   UNUSED(tbl);
 
-  rb_gc_mark((VALUE) key);
+  rb_gc_mark((VALUE)key);
 
   if (!value)
     return ST_CONTINUE;
 
-  rb_gc_mark((VALUE) value);
+  rb_gc_mark((VALUE)value);
 
   return ST_CONTINUE;
 }
@@ -27,16 +27,16 @@ t_tbl_mark_keyvalue(st_data_t key, st_data_t value, st_data_t tbl)
 static void
 t_tbl_mark(void *data)
 {
-  threads_table_t *t_tbl = (threads_table_t *) data;
+  threads_table_t *t_tbl = (threads_table_t *)data;
   st_table *tbl = t_tbl->tbl;
 
-  st_foreach(tbl, t_tbl_mark_keyvalue, (st_data_t) tbl);
+  st_foreach(tbl, t_tbl_mark_keyvalue, (st_data_t)tbl);
 }
 
 static void
 t_tbl_free(void *data)
 {
-  threads_table_t *t_tbl = (threads_table_t *) data;
+  threads_table_t *t_tbl = (threads_table_t *)data;
 
   st_free_table(t_tbl->tbl);
   xfree(t_tbl);
@@ -70,7 +70,7 @@ check_thread_i(st_data_t key, st_data_t value, st_data_t data)
   if (!value)
     return ST_DELETE;
 
-  if (!is_living_thread((VALUE) key))
+  if (!is_living_thread((VALUE)key))
     return ST_DELETE;
 
   return ST_CONTINUE;
@@ -110,7 +110,7 @@ cleanup_dead_threads(void)
  * Looks up a context in the threads table. If not present, it creates it.
  */
 void
-thread_context_lookup(VALUE thread, VALUE * context)
+thread_context_lookup(VALUE thread, VALUE *context)
 {
   threads_table_t *t_tbl;
 
@@ -129,7 +129,7 @@ thread_context_lookup(VALUE thread, VALUE * context)
  * Thanks to this, all threads are "frozen" while the user is typing commands.
  */
 void
-acquire_lock(debug_context_t * dc)
+acquire_lock(debug_context_t *dc)
 {
   while ((!NIL_P(locker) && locker != rb_thread_current())
          || CTX_FL_TEST(dc, CTX_FL_SUSPEND))