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Add Io_progress_handler to Entrypoint interface

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The "schedule_post_signal_hook" method of the Genode::Entrypoint class
is problematic because the signal hook can be scheduled and replaced
multiple times during the signal dispatch cycle. Add an alternative to
this method with "register_io_progress_handler" and the "Post_signal_
hook" class with "Io_progress_handler". The difference being an
"Io_progress_handler" may be registered once during the lifetime of an
entrypoint to prevent arbitrary libraries from replacing a pending hook.

The "register_io_progress_handler" remains as a deprecated API, and is
now invoked for every I/O signal received and only for I/O signals
rather than for any signal.

Ref #3132
This commit is contained in:
Emery Hemingway 2019-02-05 15:31:21 +01:00 committed by Christian Helmuth
parent 93fb79f357
commit 57fd4e9148
5 changed files with 134 additions and 116 deletions
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47
repos/base/include/base/entrypoint.h
View File

@ -5,7 +5,7 @@
*/
/*
* Copyright (C) 2015-2017 Genode Labs GmbH
* Copyright (C) 2015-2019 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
@ -31,8 +31,28 @@ class Genode::Entrypoint : Noncopyable
{
public:
/**
* Functor for post I/O signal progress handling
*
* This mechanism is for processing I/O events
* deferred during signal dispatch. This is the
* case when the application is blocked by I/O
* but should not be resumed during signal
* dispatch.
*/
struct Io_progress_handler : Interface
{
virtual ~Io_progress_handler() {
error("Io_progress_handler subclass cannot be safely destroyed!"); }
virtual void handle_io_progress() = 0;
};
/**
* Functor for post signal-handler hook
*
* \deprecated
* \noapi
*/
struct Post_signal_hook : Interface { virtual void function() = 0; };
@ -96,7 +116,15 @@ class Genode::Entrypoint : Noncopyable
int _signal_recipient { NONE };
Genode::Lock _signal_pending_lock { };
Genode::Lock _signal_pending_ack_lock { };
Post_signal_hook *_post_signal_hook = nullptr;
Io_progress_handler *_io_progress_handler { nullptr };
Post_signal_hook *_post_signal_hook { nullptr };
void _handle_io_progress()
{
if (_io_progress_handler != nullptr)
_io_progress_handler->handle_io_progress();
}
void _execute_post_signal_hook()
{
@ -220,8 +248,23 @@ class Genode::Entrypoint : Noncopyable
*/
void schedule_suspend(void (*suspended)(), void (*resumed)());
/**
* Register hook functor to be called after I/O signals are dispatched
*/
void register_io_progress_handler(Io_progress_handler &handler)
{
if (_io_progress_handler != nullptr) {
error("cannot call ", __func__, " twice!");
throw Exception();
}
_io_progress_handler = &handler;
}
/**
* Register hook functor to be called after signal was handled
*
* \deprecated
* \noapi
*/
void schedule_post_signal_hook(Post_signal_hook *hook)
{

27
repos/base/src/lib/base/entrypoint.cc
View File

@ -6,7 +6,7 @@
*/
/*
* Copyright (C) 2015-2017 Genode Labs GmbH
* Copyright (C) 2015-2019 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
@ -43,14 +43,30 @@ static char const *initial_ep_name() { return "ep"; }
void Entrypoint::Signal_proxy_component::signal()
{
/* XXX introduce while-pending loop */
ep._process_deferred_signals();
bool io_progress = false;
/*
* Try to dispatch one pending signal picked-up by the signal-proxy thread.
* Note, we handle only one signal here to ensure fairness between RPCs and
* signals.
*/
try {
Signal sig = ep._sig_rec->pending_signal();
ep._dispatch_signal(sig);
if (sig.context()->level() == Signal_context::Level::Io) {
/* trigger the progress handler */
io_progress = true;
/* execute deprecated per-signal hook */
ep._execute_post_signal_hook();
}
} catch (Signal_receiver::Signal_not_pending) { }
ep._execute_post_signal_hook();
ep._process_deferred_signals();
if (io_progress)
ep._handle_io_progress();
}
@ -198,6 +214,7 @@ bool Entrypoint::_wait_and_dispatch_one_io_signal(bool const dont_block)
}
_dispatch_signal(sig);
_execute_post_signal_hook();
break;
} catch (Signal_receiver::Signal_not_pending) {
@ -211,7 +228,7 @@ bool Entrypoint::_wait_and_dispatch_one_io_signal(bool const dont_block)
}
}
_execute_post_signal_hook();
_handle_io_progress();
/* initiate potential deferred-signal handling in entrypoint */
if (_deferred_signals.first()) {

99
repos/libports/src/lib/libc/task.cc
View File

@ -6,7 +6,7 @@
*/
/*
* Copyright (C) 2016-2018 Genode Labs GmbH
* Copyright (C) 2016-2019 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
@ -20,8 +20,7 @@
#include <base/rpc_client.h>
#include <base/heap.h>
#include <base/attached_rom_dataspace.h>
#include <vfs/file_system_factory.h>
#include <vfs/dir_file_system.h>
#include <vfs/simple_env.h>
#include <timer_session/connection.h>
/* libc includes */
@ -40,60 +39,17 @@ extern char **environ;
namespace Libc {
class Env_implementation;
class Vfs_env;
class Kernel;
class Pthreads;
class Timer;
class Timer_accessor;
class Timeout;
class Timeout_handler;
class Io_response_handler;
using Genode::Microseconds;
}
class Libc::Vfs_env : public Vfs::Env
{
private:
Genode::Env &_env;
Genode::Allocator &_alloc;
Vfs::Io_response_handler &_io_handler;
struct Watch_response_stub : Vfs::Watch_response_handler {
void handle_watch_response(Vfs::Vfs_watch_handle::Context*) override { };
} _watch_stub { };
Vfs::Global_file_system_factory _global_file_system_factory { _alloc };
Vfs::Dir_file_system _root_dir;
public:
Vfs_env(Genode::Env &env,
Genode::Allocator &alloc,
Genode::Xml_node config,
Vfs::Io_response_handler &io_handler)
: _env(env), _alloc(alloc), _io_handler(io_handler),
_root_dir(*this, config, _global_file_system_factory)
{ }
Genode::Env &env() override { return _env; }
Genode::Allocator &alloc() override { return _alloc; }
Vfs::File_system &root_dir() override { return _root_dir; }
Vfs::Io_response_handler &io_handler() override {
return _io_handler; }
Vfs::Watch_response_handler &watch_handler() override {
return _watch_stub; }
};
class Libc::Env_implementation : public Libc::Env
{
private:
@ -126,20 +82,15 @@ class Libc::Env_implementation : public Libc::Env
return Genode::Xml_node("<libc/>");
}
Vfs::Global_file_system_factory _file_system_factory;
Vfs_env _vfs_env;
Vfs::Simple_env _vfs_env;
Genode::Xml_node _config_xml() const override {
return _config.xml(); };
public:
Env_implementation(Genode::Env &env, Genode::Allocator &alloc,
Vfs::Io_response_handler &io_response_handler)
:
_env(env), _file_system_factory(alloc),
_vfs_env(_env, alloc, _vfs_config(), io_response_handler)
{ }
Env_implementation(Genode::Env &env, Genode::Allocator &alloc)
: _env(env), _vfs_env(_env, alloc, _vfs_config()) { }
/*************************
@ -371,19 +322,6 @@ struct Libc::Pthreads
extern void (*libc_select_notify)();
struct Libc::Io_response_handler : Vfs::Io_response_handler
{
void handle_io_response(Vfs::Vfs_handle::Context *) override
{
/* some contexts may have been deblocked from select() */
if (libc_select_notify)
libc_select_notify();
/* resume all as any context may have been deblocked from blocking I/O */
Libc::resume_all();
}
};
/* internal utility */
static void resumed_callback();
@ -400,14 +338,14 @@ static void suspended_callback();
* secondary stack for the application task. Context switching uses
* setjmp/longjmp.
*/
struct Libc::Kernel
struct Libc::Kernel final : Genode::Entrypoint::Io_progress_handler
{
private:
Genode::Env &_env;
Genode::Allocator &_heap;
Io_response_handler _io_response_handler;
Env_implementation _libc_env { _env, _heap, _io_response_handler };
Env_implementation _libc_env { _env, _heap };
Vfs_plugin _vfs { _libc_env, _heap };
Genode::Reconstructible<Genode::Io_signal_handler<Kernel>> _resume_main_handler {
@ -619,7 +557,10 @@ struct Libc::Kernel
public:
Kernel(Genode::Env &env, Genode::Allocator &heap)
: _env(env), _heap(heap) { }
: _env(env), _heap(heap)
{
_env.ep().register_io_progress_handler(*this);
}
~Kernel() { Genode::error(__PRETTY_FUNCTION__, " should not be executed!"); }
@ -821,6 +762,22 @@ struct Libc::Kernel
_switch_to_user();
}
}
/**
* Entrypoint::Io_progress_handler interface
*/
void handle_io_progress() override
{
/* some contexts may have been deblocked from select() */
if (libc_select_notify)
libc_select_notify();
/*
* resume all as any VFS context may have
* been deblocked from blocking I/O
*/
Kernel::resume_all();
}
};

45
repos/os/src/lib/vfs/fs_file_system.h
View File

@ -370,8 +370,7 @@ class Vfs::Fs_file_system : public File_system
Io_response_handler &_io_handler;
Watch_response_handler &_watch_handler;
List<Vfs_handle::Context> _context_list { };
List<Vfs_watch_handle::Context>
_watch_context_list { };
Lock _list_lock { };
bool _notify_all { false };
@ -406,27 +405,6 @@ class Vfs::Fs_file_system : public File_system
_ep.schedule_post_signal_hook(this);
}
void arm_watch_event(Vfs_watch_handle::Context &context)
{
{
Lock::Guard list_guard(_list_lock);
for (Vfs_watch_handle::Context *list_context = _watch_context_list.first();
list_context;
list_context = list_context->next())
{
if (list_context == &context) {
/* already in list */
return;
}
}
_watch_context_list.insert(&context);
}
_ep.schedule_post_signal_hook(this);
}
void function() override
{
Vfs_handle::Context *context = nullptr;
@ -451,18 +429,6 @@ class Vfs::Fs_file_system : public File_system
/* done if no contexts and all notified */
} while (context);
for (;;) {
Vfs_watch_handle::Context *context = nullptr;
{
Lock::Guard list_guard(_list_lock);
context = _watch_context_list.first();
if (!context) break;
_watch_context_list.remove(context);
_watch_handler.handle_watch_response(context);
}
}
}
};
@ -609,9 +575,14 @@ class Vfs::Fs_file_system : public File_system
try {
if (packet.operation() == Packet_descriptor::CONTENT_CHANGED) {
/*
* Trigger the watch response during signal dispatch.
* This is incompatible with the Libc I/O handling
* but the Libc does not open watch handles and shall
* not use them before Post_signal_hook is removed.
*/
_watch_handle_space.apply<Fs_vfs_watch_handle>(id, [&] (Fs_vfs_watch_handle &handle) {
if (auto *ctx = handle.context())
_post_signal_hook.arm_watch_event(*ctx); });
_env.watch_handler().handle_watch_response(handle.context()); });
} else {
_handle_space.apply<Fs_vfs_handle>(id, handle_read);
}

32
repos/os/src/server/vfs/main.cc
View File

@ -712,8 +712,9 @@ class Vfs_server::Session_component : private Session_resources,
void control(Node_handle, Control) override { }
};
/**
* Global I/O event handler
* Global VFS event handler
*/
struct Vfs_server::Io_response_handler : Vfs::Io_response_handler
{
@ -751,6 +752,7 @@ struct Vfs_server::Io_response_handler : Vfs::Io_response_handler
}
};
/**
* Global VFS watch handler
*/
@ -822,6 +824,34 @@ class Vfs_server::Root : public Genode::Root_component<Session_component>
Vfs_env _vfs_env { _env, vfs_config(), _session_registry };
/**
* Global I/O event handler
*
* This is a safe and slow intermediate implementation
* to be replaced with one that only processes handles
* and sessions that await progress.
*/
struct Io_progress_handler : Genode::Entrypoint::Io_progress_handler
{
Session_registry &_session_registry;
Io_progress_handler(Genode::Entrypoint &ep,
Session_registry &session_registry)
: _session_registry(session_registry)
{
ep.register_io_progress_handler(*this);
}
/**
* Entrypoint::Io_progress_handler interface
*/
void handle_io_progress() override
{
_session_registry.for_each([ ] (Registered_session &r) {
r.handle_general_io(); });
}
} _io_progress_handler { _env.ep(), _session_registry };
Genode::Signal_handler<Root> _config_handler {
_env.ep(), *this, &Root::_config_update };