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A user pointed out that the build failed with GCC 4.8. The problem
was that the form used by the std::hash specialization of ptid_t was
not accepted. This patch rewrites this code into a form that is
acceptable to the older compiler.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This changes hash_ptid to instead be a specialization of std::hash.
This makes it a little easier to use with standard containers.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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A following patch will want to declare variables of the same type as
some ptid_t components. To make that easy (and avoid harcoding those
types everywhere), define some type definitions in the ptid_t struct for
each of them. Use them throughout ptid.h.
I initially used pid_t, lwp_t and tid_t, but there is the risk of some
system defining the pid_t type using a macro instead of a typedef, which
would break things. So, use the _type suffix instead.
Change-Id: I820b0bea9dafcb4914f1c9ba4bb96b5c666c8dec
Approved-By: Andrew Burgess <aburgess@redhat.com>
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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.
For the avoidance of doubt, all changes in this commits were
performed by the script.
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The ptid_t 'tid' member is normally used as an address in gdb -- both
bsd-uthread and ravenscar-thread use it this way. However, because
the type is 'long', this can cause problems with sign extension.
This patch changes the type to ULONGEST to ensure that sign extension
does not occur.
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status
Looking up threads that are both resumed and have a pending wait
status to report is something that we do quite often in the fast path
and is expensive if there are many threads, since it currently requires
walking whole thread lists.
The first instance is in maybe_set_commit_resumed_all_targets. This is
called after handling each event in fetch_inferior_event, to see if we
should ask targets to commit their resumed threads or not. If at least
one thread is resumed but has a pending wait status, we don't ask the
targets to commit their resumed threads, because we want to consume and
handle the pending wait status first.
The second instance is in random_pending_event_thread, where we want to
select a random thread among all those that are resumed and have a
pending wait status. This is called every time we try to consume
events, to see if there are any pending events that we we want to
consume, before asking the targets for more events.
To allow optimizing these cases, maintain a per-process-target list of
threads that are resumed and have a pending wait status.
In maybe_set_commit_resumed_all_targets, we'll be able to check in O(1)
if there are any such threads simply by checking whether the list is
empty.
In random_pending_event_thread, we'll be able to use that list, which
will be quicker than iterating the list of threads, especially when
there are no resumed with pending wait status threads.
About implementation details: using the new setters on class
thread_info, it's relatively easy to maintain that list. Any time the
"resumed" or "pending wait status" property is changed, we check whether
that should cause the thread to be added or removed from the list.
In set_thread_exited, we try to remove the thread from the list, because
keeping an exited thread in that list would make no sense (especially if
the thread is freed). My first implementation assumed that a process
stratum target was always present when set_thread_exited is called.
That's however, not the case: in some cases, targets unpush themselves
from an inferior and then call "exit_inferior", which exits all the
threads. If the target is unpushed before set_thread_exited is called
on the threads, it means we could mistakenly leave some threads in the
list. I tried to see how hard it would be to make it such that targets
have to exit all threads before unpushing themselves from the inferior
(that would seem logical to me, we don't want threads belonging to an
inferior that has no process target). That seemed quite difficult and
not worth the time at the moment. Instead, I changed
inferior::unpush_target to remove all threads of that inferior from the
list.
As of this patch, the list is not used, this is done in the subsequent
patches.
The debug messages in process-stratum-target.c need to print some ptids.
However, they can't use target_pid_to_str to print them without
introducing a dependency on the current inferior (the current inferior
is used to get the current target stack). For debug messages, I find it
clearer to print the spelled out ptid anyway (the pid, lwp and tid
values). Add a ptid_t::to_string method that returns a string
representation of the ptid that is meant for debug messages, a bit like
we already have frame_id::to_string.
Change-Id: Iad8f93db2d13984dd5aa5867db940ed1169dbb67
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This commits the result of running gdb/copyright.py as per our Start
of New Year procedure...
gdb/ChangeLog
Update copyright year range in copyright header of all GDB files.
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One regcache object is created for each stopped thread and is stored in
the regcache::regcaches linked list. Looking up a regcache for a given
thread is therefore in O(number of threads). Stopping all threads then
becomes O((number of threads) ^ 2). Same goes for resuming a thread
(need to delete the regcache of a given ptid) and resuming all threads.
It becomes noticeable when debugging thousands of threads, which is
typical with GPU targets. This patch replaces the linked list with some
maps to reduce that complexity.
The first design was using an std::unordered_map with (target, ptid,
arch) as the key, because that's how lookups are done (in
get_thread_arch_aspace_regcache). However, the registers_changed_ptid
function, also somewhat on the hot path (it is used when resuming
threads), needs to delete all regcaches associated to a given (target,
ptid) tuple. If the key of the map is (target, ptid, arch), we have to
walk all items of the map, not good.
The second design was therefore using an std::unordered_multimap with
(target, ptid) as the key. One key could be associated to multiple
regcaches, all with different gdbarches. When looking up, we would have
to walk all these regcaches. This would be ok, because there will
usually be actually one matching regcache. In the exceptional
multi-arch thread cases, there will be maybe two. However, in
registers_changed_ptid, we sometimes need to remove all regcaches
matching a given target. We would then have to talk all items of the
map again, not good.
The design as implemented in this patch therefore uses two levels of
map. One std::unordered_map uses the target as the key. The value type
is an std::unordered_multimap that itself uses the ptid as the key. The
values of the multimap are the regcaches themselves. Again, we expect
to have one or very few regcaches per (target, ptid).
So, in summary:
* The lookups (in get_thread_arch_aspace_regcache), become faster when
the number of threads grows, compared to the linked list. With a
small number of threads, it will probably be a bit slower to do map
lookups than to walk a few linked list nodes, but I don't think it
will be noticeable in practice.
* The function registers_changed_ptid deletes all regcaches related to a
given (target, ptid). It must now handle the different cases separately:
- NULL target and minus_one_ptid: we delete all the entries
- NULL target and non-minus_one_ptid: invalid (checked by assert)
- non-NULL target and non-minus_one_ptid: we delete all the entries
associated to that tuple
- a non-NULL target and minus_one_ptid: we delete all the entries
associated to that target
* The function regcache_thread_ptid_changed is called when a thread
changes ptid. It is implemented efficiently using the map, although
that's not very important: it is not called often, mostly when
creating an inferior, on some specific platforms.
This patch is a tiny bit from ROCm GDB [1] we would like to merge
upstream. Laurent Morichetti gave be these performance numbers:
The benchmark used is:
time ./gdb --data-directory=data-directory /extra/lmoriche/hip/samples/0_Intro/bit_extract/bit_extract -ex "set pagination off" -ex "set breakpoint pending on" -ex "b bit_extract_kernel if \$_thread == 5" -ex run -ex c -batch
It measures the time it takes to continue from a conditional breakpoint with
2048 threads at that breakpoint, one of them reporting the breakpoint.
baseline:
real 0m10.227s
real 0m10.177s
real 0m10.362s
with patch:
real 0m8.356s
real 0m8.424s
real 0m8.494s
[1] https://github.com/ROCm-Developer-Tools/ROCgdb
gdb/ChangeLog:
* regcache.c (ptid_regcache_map): New type.
(target_ptid_regcache_map): New type.
(regcaches): Change type to target_ptid_regcache_map.
(get_thread_arch_aspace_regcache): Update to regcaches' new
type.
(regcache_thread_ptid_changed): Likewise.
(registers_changed_ptid): Likewise.
(regcaches_size): Likewise.
(regcaches_test): Update.
(regcache_thread_ptid_changed): Update.
* regcache.h (regcache_up): New type.
* gdbsupport/ptid.h (hash_ptid): New struct.
Change-Id: Iabb0a1111707936ca111ddb13f3b09efa83d3402
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This patch moves the gdbsupport directory to the top level. This is
the next step in the ongoing project to move gdbserver to the top
level.
The bulk of this patch was created by "git mv gdb/gdbsupport gdbsupport".
This patch then adds a build system to gdbsupport and wires it into
the top level. Then it changes gdb to use the top-level build.
gdbserver, on the other hand, is not yet changed. It still does its
own build of gdbsupport.
ChangeLog
2020-01-14 Tom Tromey <tom@tromey.com>
* src-release.sh (GDB_SUPPORT_DIRS): Add gdbsupport.
* MAINTAINERS: Add gdbsupport.
* configure: Rebuild.
* configure.ac (configdirs): Add gdbsupport.
* gdbsupport: New directory, move from gdb/gdbsupport.
* Makefile.def (host_modules, dependencies): Add gnulib.
* Makefile.in: Rebuild.
gdb/ChangeLog
2020-01-14 Tom Tromey <tom@tromey.com>
* nat/x86-linux-dregs.c: Include configh.h.
* nat/linux-ptrace.c: Include configh.h.
* nat/linux-btrace.c: Include configh.h.
* defs.h: Include config.h, bfd.h.
* configure.ac: Don't source common.host.
(CONFIG_OBS, CONFIG_SRCS): Remove gdbsupport files.
* configure: Rebuild.
* acinclude.m4: Update path.
* Makefile.in (SUPPORT, LIBSUPPORT, INCSUPPORT): New variables.
(CONFIG_SRC_SUBDIR): Remove gdbsupport.
(INTERNAL_CFLAGS_BASE): Add INCSUPPORT.
(CLIBS): Add LIBSUPPORT.
(CDEPS): Likewise.
(COMMON_SFILES): Remove gdbsupport files.
(HFILES_NO_SRCDIR): Likewise.
(stamp-version): Update path to create-version.sh.
(ALLDEPFILES): Remove gdbsupport files.
gdb/gdbserver/ChangeLog
2020-01-14 Tom Tromey <tom@tromey.com>
* server.h: Include config.h.
* gdbreplay.c: Include config.h.
* configure: Rebuild.
* configure.ac: Don't source common.host.
* acinclude.m4: Update path.
* Makefile.in (INCSUPPORT): New variable.
(INCLUDE_CFLAGS): Add INCSUPPORT.
(SFILES): Update paths.
(version-generated.c): Update path to create-version.sh.
(gdbsupport/%-ipa.o, gdbsupport/%.o): Update paths.
gdbsupport/ChangeLog
2020-01-14 Tom Tromey <tom@tromey.com>
* common-defs.h: Add GDBSERVER case. Update includes.
* acinclude.m4, aclocal.m4, config.in, configure, configure.ac,
Makefile.am, Makefile.in, README: New files.
* Moved from ../gdb/gdbsupport/
Change-Id: I07632e7798635c1bab389bf885971e584fb4bb78
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