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gdb: use intrusive list for step-over chain

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The threads that need a step-over are currently linked using an
hand-written intrusive doubly-linked list, so that seems a very good
candidate for intrusive_list, convert it.

For this, we have a use case of appending a list to another one (in
start_step_over).  Based on the std::list and Boost APIs, add a splice
method.  However, only support splicing the other list at the end of the
`this` list, since that's all we need.

Add explicit default assignment operators to
reference_to_pointer_iterator, which are otherwise implicitly deleted.
This is needed because to define thread_step_over_list_safe_iterator, we
wrap reference_to_pointer_iterator inside a basic_safe_iterator, and
basic_safe_iterator needs to be able to copy-assign the wrapped
iterator.  The move-assignment operator is therefore not needed, only
the copy-assignment operator is.  But for completeness, add both.

Change-Id: I31b2ff67c7b78251314646b31887ef1dfebe510c
This commit is contained in:
Simon Marchi 2021-06-15 14:49:32 -04:00
parent 08bdefb58b
commit 8b6a69b2f3
7 changed files with 177 additions and 138 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
gdb/gdbthread.h
View File

@ -387,11 +387,9 @@ public:
expressions. */
std::vector<struct value *> stack_temporaries;
/* Step-over chain. A thread is in the step-over queue if these are
non-NULL. If only a single thread is in the chain, then these
fields point to self. */
struct thread_info *step_over_prev = NULL;
struct thread_info *step_over_next = NULL;
/* Step-over chain. A thread is in the step-over queue if this node is
linked. */
intrusive_list_node<thread_info> step_over_list_node;
/* Displaced-step state for this thread. */
displaced_step_thread_state displaced_step_state;
@ -742,36 +740,42 @@ extern value *get_last_thread_stack_temporary (struct thread_info *tp);
extern bool value_in_thread_stack_temporaries (struct value *,
struct thread_info *thr);
/* Thread step-over list type. */
using thread_step_over_list_node
= intrusive_member_node<thread_info, &thread_info::step_over_list_node>;
using thread_step_over_list
= intrusive_list<thread_info, thread_step_over_list_node>;
using thread_step_over_list_iterator
= reference_to_pointer_iterator<thread_step_over_list::iterator>;
using thread_step_over_list_safe_iterator
= basic_safe_iterator<thread_step_over_list_iterator>;
using thread_step_over_list_safe_range
= iterator_range<thread_step_over_list_safe_iterator>;
static inline thread_step_over_list_safe_range
make_thread_step_over_list_safe_range (thread_step_over_list &list)
{
return thread_step_over_list_safe_range
(thread_step_over_list_safe_iterator (list.begin (),
list.end ()),
thread_step_over_list_safe_iterator (list.end (),
list.end ()));
}
/* Add TP to the end of the global pending step-over chain. */
extern void global_thread_step_over_chain_enqueue (thread_info *tp);
/* Append the thread step over chain CHAIN_HEAD to the global thread step over
/* Append the thread step over list LIST to the global thread step over
chain. */
extern void global_thread_step_over_chain_enqueue_chain
(thread_info *chain_head);
/* Remove TP from step-over chain LIST_P. */
extern void thread_step_over_chain_remove (thread_info **list_p,
thread_info *tp);
(thread_step_over_list &&list);
/* Remove TP from the global pending step-over chain. */
extern void global_thread_step_over_chain_remove (thread_info *tp);
/* Return the thread following TP in the step-over chain whose head is
CHAIN_HEAD. Return NULL if TP is the last entry in the chain. */
extern thread_info *thread_step_over_chain_next (thread_info *chain_head,
thread_info *tp);
/* Return the thread following TP in the global step-over chain, or NULL if TP
is the last entry in the chain. */
extern thread_info *global_thread_step_over_chain_next (thread_info *tp);
/* Return true if TP is in any step-over chain. */
extern int thread_is_in_step_over_chain (struct thread_info *tp);
@ -782,7 +786,7 @@ extern int thread_is_in_step_over_chain (struct thread_info *tp);
TP may be nullptr, in which case it denotes an empty list, so a length of
0. */
extern int thread_step_over_chain_length (thread_info *tp);
extern int thread_step_over_chain_length (const thread_step_over_list &l);
/* Cancel any ongoing execution command. */

39
gdb/infrun.c
View File

@ -1245,7 +1245,7 @@ follow_exec (ptid_t ptid, const char *exec_file_target)
to avoid starvation, otherwise, we could e.g., find ourselves
constantly stepping the same couple threads past their breakpoints
over and over, if the single-step finish fast enough. */
struct thread_info *global_thread_step_over_chain_head;
thread_step_over_list global_thread_step_over_list;
/* Bit flags indicating what the thread needs to step over. */
@ -1843,8 +1843,6 @@ start_step_over (void)
{
INFRUN_SCOPED_DEBUG_ENTER_EXIT;
thread_info *next;
/* Don't start a new step-over if we already have an in-line
step-over operation ongoing. */
if (step_over_info_valid_p ())
@ -1854,8 +1852,8 @@ start_step_over (void)
steps, threads will be enqueued in the global chain if no buffers are
available. If we iterated on the global chain directly, we might iterate
indefinitely. */
thread_info *threads_to_step = global_thread_step_over_chain_head;
global_thread_step_over_chain_head = NULL;
thread_step_over_list threads_to_step
= std::move (global_thread_step_over_list);
infrun_debug_printf ("stealing global queue of threads to step, length = %d",
thread_step_over_chain_length (threads_to_step));
@ -1867,18 +1865,22 @@ start_step_over (void)
global list. */
SCOPE_EXIT
{
if (threads_to_step == nullptr)
if (threads_to_step.empty ())
infrun_debug_printf ("step-over queue now empty");
else
{
infrun_debug_printf ("putting back %d threads to step in global queue",
thread_step_over_chain_length (threads_to_step));
global_thread_step_over_chain_enqueue_chain (threads_to_step);
global_thread_step_over_chain_enqueue_chain
(std::move (threads_to_step));
}
};
for (thread_info *tp = threads_to_step; tp != NULL; tp = next)
thread_step_over_list_safe_range range
= make_thread_step_over_list_safe_range (threads_to_step);
for (thread_info *tp : range)
{
struct execution_control_state ecss;
struct execution_control_state *ecs = &ecss;
@ -1887,8 +1889,6 @@ start_step_over (void)
gdb_assert (!tp->stop_requested);
next = thread_step_over_chain_next (threads_to_step, tp);
if (tp->inf->displaced_step_state.unavailable)
{
/* The arch told us to not even try preparing another displaced step
@ -1903,7 +1903,7 @@ start_step_over (void)
step over chain indefinitely if something goes wrong when resuming it
If the error is intermittent and it still needs a step over, it will
get enqueued again when we try to resume it normally. */
thread_step_over_chain_remove (&threads_to_step, tp);
threads_to_step.erase (threads_to_step.iterator_to (*tp));
step_what = thread_still_needs_step_over (tp);
must_be_in_line = ((step_what & STEP_OVER_WATCHPOINT)
@ -3790,15 +3790,16 @@ prepare_for_detach (void)
/* Remove all threads of INF from the global step-over chain. We
want to stop any ongoing step-over, not start any new one. */
thread_info *next;
for (thread_info *tp = global_thread_step_over_chain_head;
tp != nullptr;
tp = next)
{
next = global_thread_step_over_chain_next (tp);
if (tp->inf == inf)
thread_step_over_list_safe_range range
= make_thread_step_over_list_safe_range (global_thread_step_over_list);
for (thread_info *tp : range)
if (tp->inf == inf)
{
infrun_debug_printf ("removing thread %s from global step over chain",
target_pid_to_str (tp->ptid).c_str ());
global_thread_step_over_chain_remove (tp);
}
}
/* If we were already in the middle of an inline step-over, and the
thread stepping belongs to the inferior we're detaching, we need

4
gdb/infrun.h
View File

@ -18,8 +18,10 @@
#ifndef INFRUN_H
#define INFRUN_H 1
#include "gdbthread.h"
#include "symtab.h"
#include "gdbsupport/byte-vector.h"
#include "gdbsupport/intrusive_list.h"
struct target_waitstatus;
struct frame_info;
@ -253,7 +255,7 @@ extern void mark_infrun_async_event_handler (void);
/* The global chain of threads that need to do a step-over operation
to get past e.g., a breakpoint. */
extern struct thread_info *global_thread_step_over_chain_head;
extern thread_step_over_list global_thread_step_over_list;
/* Remove breakpoints if possible (usually that means, if everything
is stopped). On failure, print a message. */

106
gdb/thread.c
View File

@ -183,7 +183,7 @@ void
set_thread_exited (thread_info *tp, bool silent)
{
/* Dead threads don't need to step-over. Remove from chain. */
if (tp->step_over_next != NULL)
if (thread_is_in_step_over_chain (tp))
global_thread_step_over_chain_remove (tp);
if (tp->state != THREAD_EXITED)
@ -293,93 +293,22 @@ thread_info::deletable () const
return refcount () == 0 && !is_current_thread (this);
}
/* Add TP to the end of the step-over chain LIST_P. */
static void
step_over_chain_enqueue (struct thread_info **list_p, struct thread_info *tp)
{
gdb_assert (tp->step_over_next == NULL);
gdb_assert (tp->step_over_prev == NULL);
if (*list_p == NULL)
{
*list_p = tp;
tp->step_over_prev = tp->step_over_next = tp;
}
else
{
struct thread_info *head = *list_p;
struct thread_info *tail = head->step_over_prev;
tp->step_over_prev = tail;
tp->step_over_next = head;
head->step_over_prev = tp;
tail->step_over_next = tp;
}
}
/* See gdbthread.h. */
void
thread_step_over_chain_remove (thread_info **list_p, thread_info *tp)
{
gdb_assert (tp->step_over_next != NULL);
gdb_assert (tp->step_over_prev != NULL);
if (*list_p == tp)
{
if (tp == tp->step_over_next)
*list_p = NULL;
else
*list_p = tp->step_over_next;
}
tp->step_over_prev->step_over_next = tp->step_over_next;
tp->step_over_next->step_over_prev = tp->step_over_prev;
tp->step_over_prev = tp->step_over_next = NULL;
}
/* See gdbthread.h. */
thread_info *
thread_step_over_chain_next (thread_info *chain_head, thread_info *tp)
{
thread_info *next = tp->step_over_next;
return next == chain_head ? NULL : next;
}
/* See gdbthread.h. */
struct thread_info *
global_thread_step_over_chain_next (struct thread_info *tp)
{
return thread_step_over_chain_next (global_thread_step_over_chain_head, tp);
}
/* See gdbthread.h. */
int
thread_is_in_step_over_chain (struct thread_info *tp)
{
return (tp->step_over_next != NULL);
return tp->step_over_list_node.is_linked ();
}
/* See gdbthread.h. */
int
thread_step_over_chain_length (thread_info *tp)
thread_step_over_chain_length (const thread_step_over_list &l)
{
if (tp == nullptr)
return 0;
gdb_assert (thread_is_in_step_over_chain (tp));
int num = 1;
for (thread_info *iter = tp->step_over_next;
iter != tp;
iter = iter->step_over_next)
for (const thread_info &thread ATTRIBUTE_UNUSED : l)
++num;
return num;
@ -393,29 +322,16 @@ global_thread_step_over_chain_enqueue (struct thread_info *tp)
infrun_debug_printf ("enqueueing thread %s in global step over chain",
target_pid_to_str (tp->ptid).c_str ());
step_over_chain_enqueue (&global_thread_step_over_chain_head, tp);
gdb_assert (!thread_is_in_step_over_chain (tp));
global_thread_step_over_list.push_back (*tp);
}
/* See gdbthread.h. */
void
global_thread_step_over_chain_enqueue_chain (thread_info *chain_head)
global_thread_step_over_chain_enqueue_chain (thread_step_over_list &&list)
{
gdb_assert (chain_head->step_over_next != nullptr);
gdb_assert (chain_head->step_over_prev != nullptr);
if (global_thread_step_over_chain_head == nullptr)
global_thread_step_over_chain_head = chain_head;
else
{
thread_info *global_last = global_thread_step_over_chain_head->step_over_prev;
thread_info *chain_last = chain_head->step_over_prev;
chain_last->step_over_next = global_thread_step_over_chain_head;
global_last->step_over_next = chain_head;
global_thread_step_over_chain_head->step_over_prev = chain_last;
chain_head->step_over_prev = global_last;
}
global_thread_step_over_list.splice (std::move (list));
}
/* See gdbthread.h. */
@ -426,7 +342,9 @@ global_thread_step_over_chain_remove (struct thread_info *tp)
infrun_debug_printf ("removing thread %s from global step over chain",
target_pid_to_str (tp->ptid).c_str ());
thread_step_over_chain_remove (&global_thread_step_over_chain_head, tp);
gdb_assert (thread_is_in_step_over_chain (tp));
auto it = global_thread_step_over_list.iterator_to (*tp);
global_thread_step_over_list.erase (it);
}
/* Delete the thread referenced by THR. If SILENT, don't notify
@ -810,7 +728,7 @@ set_running_thread (struct thread_info *tp, bool running)
/* If the thread is now marked stopped, remove it from
the step-over queue, so that we don't try to resume
it until the user wants it to. */
if (tp->step_over_next != NULL)
if (thread_is_in_step_over_chain (tp))
global_thread_step_over_chain_remove (tp);
}

84
gdb/unittests/intrusive_list-selftests.c
View File

@ -503,6 +503,89 @@ struct intrusive_list_test
}
}
static void
test_splice ()
{
{
/* Two non-empty lists. */
item_type a ("a"), b ("b"), c ("c"), d ("d"), e ("e");
ListType list1;
ListType list2;
std::vector<const item_type *> expected;
list1.push_back (a);
list1.push_back (b);
list1.push_back (c);
list2.push_back (d);
list2.push_back (e);
list1.splice (std::move (list2));
expected = {&a, &b, &c, &d, &e};
verify_items (list1, expected);
expected = {};
verify_items (list2, expected);
}
{
/* Receiving list empty. */
item_type a ("a"), b ("b"), c ("c");
ListType list1;
ListType list2;
std::vector<const item_type *> expected;
list2.push_back (a);
list2.push_back (b);
list2.push_back (c);
list1.splice (std::move (list2));
expected = {&a, &b, &c};
verify_items (list1, expected);
expected = {};
verify_items (list2, expected);
}
{
/* Giving list empty. */
item_type a ("a"), b ("b"), c ("c");
ListType list1;
ListType list2;
std::vector<const item_type *> expected;
list1.push_back (a);
list1.push_back (b);
list1.push_back (c);
list1.splice (std::move (list2));
expected = {&a, &b, &c};
verify_items (list1, expected);
expected = {};
verify_items (list2, expected);
}
{
/* Both lists empty. */
item_type a ("a"), b ("b"), c ("c");
ListType list1;
ListType list2;
std::vector<const item_type *> expected;
list1.splice (std::move (list2));
expected = {};
verify_items (list1, expected);
expected = {};
verify_items (list2, expected);
}
}
static void
test_pop_front ()
{
@ -682,6 +765,7 @@ test_intrusive_list ()
tests.test_push_front ();
tests.test_push_back ();
tests.test_insert ();
tests.test_splice ();
tests.test_pop_front ();
tests.test_pop_back ();
tests.test_erase ();

27
gdbsupport/intrusive_list.h
View File

@ -350,6 +350,33 @@ public:
pos_node->prev = &elem;
}
/* Move elements from LIST at the end of the current list. */
void splice (intrusive_list &&other)
{
if (other.empty ())
return;
if (this->empty ())
{
*this = std::move (other);
return;
}
/* [A ... B] + [C ... D] */
T *b_elem = m_back;
node_type *b_node = as_node (b_elem);
T *c_elem = other.m_front;
node_type *c_node = as_node (c_elem);
T *d_elem = other.m_back;
b_node->next = c_elem;
c_node->prev = b_elem;
m_back = d_elem;
other.m_front = nullptr;
other.m_back = nullptr;
}
void pop_front ()
{
gdb_assert (!this->empty ());

3
gdbsupport/reference-to-pointer-iterator.h
View File

@ -56,6 +56,9 @@ struct reference_to_pointer_iterator
reference_to_pointer_iterator (const reference_to_pointer_iterator &) = default;
reference_to_pointer_iterator (reference_to_pointer_iterator &&) = default;
reference_to_pointer_iterator &operator= (const reference_to_pointer_iterator &) = default;
reference_to_pointer_iterator &operator= (reference_to_pointer_iterator &&) = default;
value_type operator* () const
{ return &*m_it; }