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poller.C
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poller.C
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/*
** Copyright 2022 Double Precision, Inc.
** See COPYING for distribution information.
*/
#include "config.h"
#include "poller.H"
#include <sys/epoll.h>
#include <sys/inotify.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include "log.H"
#include "messages.H"
#include <unordered_map>
#include <unordered_set>
#include <tuple>
#include <algorithm>
namespace {
#if 0
}
#endif
struct global_epoll {
int epollfd;
int devnull;
int *current_timeout=nullptr;
std::unordered_map<int, std::function<void (int)>> callbacks;
global_epoll();
~global_epoll();
global_epoll(const global_epoll &)=delete;
global_epoll &operator=(const global_epoll &)=delete;
};
global_epoll &get_epoll()
{
static global_epoll global_epoll_instance;
return global_epoll_instance;
}
global_epoll::global_epoll()
{
while ((epollfd=epoll_create1(EPOLL_CLOEXEC)) == -1)
{
log_message(_("epoll_create1() failed, trying again..."));
sleep(5);
}
while ((devnull=open("/dev/null", O_RDWR | O_CLOEXEC)) == -1)
{
log_message(_("open(\"/dev/null\") failed, trying again..."));
sleep(5);
}
}
global_epoll::~global_epoll()
{
close(devnull);
close(epollfd);
devnull= -1;
epollfd= -1;
}
#if 0
{
#endif
}
polledfd::polledfd(int fd, const std::function<void (int)> &callback)
: polledfd{fd, std::function<void (int)>{callback}}
{
}
polledfd::polledfd(int fd, std::function<void (int)> &&callback)
: fd{fd}
{
auto &ep=get_epoll();
if (ep.epollfd < 0)
return; // Static initialization order fiasco.
epoll_event ev{};
ev.events=EPOLLIN | EPOLLRDHUP;
ev.data.fd=fd;
while (epoll_ctl(ep.epollfd, EPOLL_CTL_ADD, fd, &ev) < 0)
{
log_message(_("EPOLL_CTL_ADD failed, trying again..."));
sleep(5);
}
ep.callbacks[fd]=std::move(callback);
}
polledfd::~polledfd()
{
destroy();
}
void polledfd::destroy()
{
auto &ep=get_epoll();
if (fd < 0 || ep.epollfd < 0)
return; // Static initialization order fiasco.
epoll_event ev{};
while (epoll_ctl(ep.epollfd, EPOLL_CTL_DEL, fd, &ev) < 0)
{
if (errno == EBADF)
break;
log_message(_("EPOLL_CTL_DEL failed, trying again..."));
sleep(5);
}
ep.callbacks.erase(fd);
fd= -1;
}
polledfd::polledfd(polledfd &&moved_from) : polledfd{}
{
operator=(std::move(moved_from));
}
polledfd &polledfd::operator=(polledfd &&moved_from)
{
destroy();
std::swap(fd, moved_from.fd);
return *this;
}
int devnull()
{
auto &ep=get_epoll();
if (ep.epollfd < 0)
return -1;
return ep.devnull;
}
void do_poll(int timeout)
{
struct epoll_event events[10];
auto &ep=get_epoll();
if (ep.epollfd < 0)
return; // Static initialization order fiasco?
int n;
ep.current_timeout= &timeout;
bool time_updated=false;
while ((n=epoll_wait(ep.epollfd, events, std::size(events), timeout))
> 0)
{
update_current_time();
time_updated=true;
for (int i=0; i<n; ++i)
{
auto iter=ep.callbacks.find(events[i].data.fd);
if (iter == ep.callbacks.end())
continue;
iter->second(iter->first);
}
timeout=0; // Drain, but don't wait any more.
}
if (!time_updated)
update_current_time();
}
// IN_IGNORED removes the registered callback, and updates the watch handler
// which we find via the pointer.
class inotify_watch_handler::delink {
public:
inline static void update(inotify_watch_handler *me, int wd)
{
me->wd=wd;
}
};
namespace {
#if 0
}
#endif
struct global_inotify_base {
static int fd;
global_inotify_base();
~global_inotify_base();
global_inotify_base(const global_inotify_base &)=delete;
global_inotify_base &operator=(const global_inotify_base &)=delete;
};
int global_inotify_base::fd{-1};
global_inotify_base::global_inotify_base()
{
while ((fd=inotify_init1(IN_NONBLOCK | IN_CLOEXEC)) < 0)
{
log_message(_("inotify_init1() failed, trying again..."));
sleep(5);
}
}
global_inotify_base::~global_inotify_base()
{
close(fd);
fd= -1;
}
struct global_inotify;
global_inotify &get_inotify();
struct global_inotify : global_inotify_base {
public:
//! All currently active descriptors
std::unordered_map<int, std::tuple<inotify_cb_t,
inotify_watch_handler *>> installed;
//! Pending adds
std::unordered_map<inotify_watch_handler *,
std::tuple<inotify_cb_t, std::string, uint32_t>
> pending_adds;
//! Waiting rms
std::unordered_set<int> pending_rms;
private:
/*! The inotify file descriptor
This is declared last, so it gets destroyed first, before all the
maps are, because polledfd's destructor may end up accessing them.
*/
polledfd this_is_the_polled_fd;
public:
global_inotify() : this_is_the_polled_fd{fd,
[]
(int fd)
{
get_inotify().do_inotify();
}}
{
}
void do_inotify();
void do_addrm();
};
global_inotify &get_inotify()
{
static global_inotify instance;
return instance;
}
typedef inotify_watch_handler::delink delink;
void global_inotify::do_inotify()
{
if (fd < 0)
return; // Static initialization order fiasco?
// Buffer for reading the inotify events.
char buffer[(sizeof(inotify_event)+NAME_MAX+1)*4];
ssize_t n;
// Read until the non-blocking file descriptor gets drained.
while ((n=read(fd, buffer, sizeof(buffer))) > 0)
{
// Process each read inotify_event
auto b=buffer, e=buffer+n;
while (b < e)
{
auto ptr=reinterpret_cast<inotify_event *>(b);
b = b+sizeof(inotify_event)+ptr->len;
// The first order of business is to record
// the former pending_rms.
if (ptr->mask & IN_IGNORED)
pending_rms.erase(ptr->wd);
// Find the watch descriptor's installed callback.
auto iter=installed.find(ptr->wd);
if (iter == installed.end())
continue;
// Proactively reset the callback's wd upon receiving
// IN_IGNORED. If the invoked callback results in the
// destruction of the inotify_watch_handler this keeps
// things from getting hairy.
auto &[cb, watch_ptr] = iter->second;
if (ptr->mask & IN_IGNORED)
delink::update(watch_ptr, -1);
// Invoke the callback.
auto cp=ptr->name;
if (ptr->len == 0)
cp=nullptr;
cb(cp, ptr->mask);
// Then we can safely remove the installed callback.
if (ptr->mask & IN_IGNORED)
installed.erase(iter);
}
}
// Resume adding watches if they were delayed due to pending removes
// and that's been taken care of already.
while (pending_rms.empty() && !pending_adds.empty())
{
auto iter=pending_adds.begin();
auto ptr=iter->first;
auto &[cb, pathname, mask] = iter->second;
auto wd=inotify_add_watch(fd, pathname.c_str(), mask);
if (wd < 0)
{
auto cb_cpy=std::move(cb);
pending_adds.erase(iter);
cb_cpy(nullptr, IN_IGNORED);
continue;
}
delink::update(ptr, wd);
auto new_iter=installed.emplace(wd, std::tuple{
std::move(cb),
ptr
}).first;
pending_adds.erase(iter);
auto &[installed_cb, installed_ptr]=new_iter->second;
// This was a delayed install. Things could've changed.
installed_cb(nullptr, 0);
}
}
// Blocker object
std::weak_ptr<poller_transferblockObj> current_poller_transferblock;
#if 0
{
#endif
}
poller_transferblock get_poller_transferblock()
{
// Is there a blocking object in existence?
auto handler=current_poller_transferblock.lock();
if (handler)
// Ok, return it, another reference to it.
return handler;
// Create a new blocking object
handler=std::make_shared<poller_transferblockObj>();
current_poller_transferblock=handler;
return handler;
}
bool poller_is_transferrable()
{
auto handler=current_poller_transferblock.lock();
if (handler)
return false;
auto &in=get_inotify();
if (in.fd < 0)
return true; // Why not?
return in.pending_rms.empty() && in.pending_adds.empty();
}
const uint32_t inotify_watch_handler::mask_dir=
IN_CREATE | IN_CLOSE_WRITE | IN_DELETE | IN_DELETE_SELF | IN_ONLYDIR
| IN_MOVED_FROM | IN_MOVED_TO;
const uint32_t inotify_watch_handler::mask_filemodify=IN_MODIFY;
inotify_watch_handler::inotify_watch_handler(
const std::string &pathname,
uint32_t mask,
inotify_cb_t cb)
: wd{-1}, installed(false)
{
auto &in=get_inotify();
if (in.fd < 0)
return;
// If we're waiting for removed watches to be acknowledged with
// IN_IGNORE: add the new watcher to a list of pending_adds instead.
if (!in.pending_rms.empty())
{
in.pending_adds.emplace(
this,
std::tuple{
std::move(cb),
std::move(pathname),
mask
});
// We'll synthesize an IN_IGNORED if we fail to do this later.
installed=true;
return;
}
wd=inotify_add_watch(in.fd, pathname.c_str(), mask);
if (wd < 0)
return;
installed=true;
in.installed.emplace(wd, std::tuple{std::move(cb), this});
}
inotify_watch_handler::~inotify_watch_handler()
{
destroy();
}
void inotify_watch_handler::destroy()
{
auto &in=get_inotify();
if (in.fd < 0)
return;
in.pending_adds.erase(this); // Never mind
if (wd < 0)
return;
in.installed.erase(wd);
inotify_rm_watch(in.fd, wd);
in.pending_rms.insert(wd);
}
inotify_watch_handler::inotify_watch_handler(inotify_watch_handler &&o)
: inotify_watch_handler{}
{
operator=(std::move(o));
}
inotify_watch_handler &inotify_watch_handler::operator=(
inotify_watch_handler &&o
)
{
destroy();
wd=o.wd;
installed=o.installed;
// Move the watch descriptor and the installed flag.
o.wd= -1;
o.installed=false;
auto &in=get_inotify();
if (in.fd < 0)
return *this;
// Repoint the pending_adds to the moved-to object.
auto pending_iter=in.pending_adds.find(&o);
if (pending_iter != in.pending_adds.end())
{
in.pending_adds.emplace(this, std::move(pending_iter->second));
in.pending_adds.erase(pending_iter);
}
else if (wd >= 0)
{
// We must have an installed watch descriptor, if so move it.
auto iter=in.installed.find(wd);
if (iter != in.installed.end())
{
auto &[cb, ptr]=iter->second;
ptr=this;
}
}
return *this;
}
//////////////////////////////////////////////////////////////////////////
// Metadata for monitoring a single directory
struct monitor_hierarchy::monitor_info {
typedef monitor_hierarchy::changed_t changed_t;
typedef monitor_hierarchy::fatal_error_t fatal_error_t;
// The directory being monitored
std::filesystem::path dir;
// Callbacks that get invoked whenever the contents change or an
// error occurs.
std::shared_ptr<changed_t> changed;
std::shared_ptr<fatal_error_t> fatal_error;
// Callback that gets invoked when this directory entry gets deleted.
//
// It is expected that this callback will remove this monitor_info
// object.
std::function< void() > deleted;
// Subdirectories being monitored.
std::unordered_map<std::string, inotify_watch_handler> subdirs;
monitor_info(std::filesystem::path dir,
std::shared_ptr<changed_t> changed,
std::shared_ptr<fatal_error_t> fatal_error,
std::function< void() > deleted)
: dir{std::move(dir)}, changed{std::move(changed)},
fatal_error{std::move(fatal_error)},
deleted{std::move(deleted)}
{
// Read the directory and recursively monitor all subdirectories
std::error_code ec;
for (auto b=std::filesystem::directory_iterator{this->dir, ec},
e=std::filesystem::directory_iterator{}; b != e;
++b)
{
auto &entry= *b;
if (entry.is_directory())
subdirectory(
entry.path().lexically_normal(),
entry.path().filename());
}
}
monitor_info(const monitor_info &)=delete;
monitor_info &operator=(const monitor_info &)=delete;
void event(const char *, uint32_t);
void subdirectory(std::filesystem::path fullpath, std::string name);
};
// inotify callback for some event.
void monitor_hierarchy::monitor_info::event(const char *pathname, uint32_t mask)
{
// For the purposes of monitoring a directory with an absolute
// path, IN_MOVE_SELF is equivalent to the directory being removed.
if (mask & (IN_IGNORED | IN_MOVE_SELF | IN_DELETE_SELF))
{
deleted();
return;
}
if ((mask & IN_CREATE) && pathname)
{
auto fullpath=(dir / pathname).lexically_normal();
std::error_code ec;
std::filesystem::directory_entry new_entry{fullpath, ec};
if (!ec && new_entry.is_directory())
subdirectory(fullpath, pathname);
else if (ec || !new_entry.is_regular_file())
return;
(*changed)(pathname);
return;
}
if (mask & (IN_CLOSE_WRITE | IN_CREATE | IN_DELETE |
IN_MOVED_FROM | IN_MOVED_TO))
{
(*changed)(pathname);
}
}
void monitor_hierarchy::monitor_info::subdirectory(
std::filesystem::path fullpath,
std::string name)
{
auto copy=fullpath;
inotify_watch_handler new_handler{
std::move(copy),
inotify_watch_handler::mask_dir,
[info=std::make_shared<monitor_info>(
std::move(fullpath),
changed,
fatal_error,
[this, name]
{
subdirs.erase(name);
})]
(const char *pathname, auto mask)
{
info->event(pathname, mask);
}
};
if (!new_handler)
{
(*fatal_error)(
static_cast<std::string>(fullpath) +
_(": cannot open directory for monitoring"));
return;
}
subdirs.emplace(std::move(name), std::move(new_handler));
}
monitor_hierarchy::monitor_hierarchy(
const std::filesystem::path &dir,
changed_t changed,
fatal_error_t fatal_error
) : monitor_hierarchy{dir.lexically_normal(), changed,
std::make_shared<fatal_error_t>(std::move(fatal_error))}
{
}
monitor_hierarchy::monitor_hierarchy(
std::filesystem::path dir,
changed_t &changed,
std::shared_ptr<fatal_error_t> fatal_error
) : monitor_hierarchy{
std::make_shared<monitor_info>(
dir,
std::make_shared<changed_t>(std::move(changed)),
fatal_error,
[this, fatal_error, dir]
{
// We must make a copy of everything.
//
// The call to operator= removes the watch.
// We want to do that because IN_DELETE_SELF
// will get followed by IN_IGNORED, that will
// end up here again, and we want to be nice
// by logging the error just once.
//
// No good deed goes unpunished. This closure
// because a part of a shared_ptr-based object
// that gets destroyed by operator=, so by the
// time we get back here this closure get
// *destroyed*. So we intentionally make a copy
// of fatal_error in automatic scope just for
// so that we can reference it after we
// return!
auto cpy_fatal_error=fatal_error;
auto cpy_dir=dir;
inotify_watch_handler::operator=(
inotify_watch_handler{}
);
(*cpy_fatal_error)(
static_cast<std::string>(cpy_dir)
+ _(": unexpectedly removed!")
);
}
)
}
{
}
monitor_hierarchy::monitor_hierarchy(std::shared_ptr<monitor_info> info)
: inotify_watch_handler{info->dir, mask_dir,
[info]
(const char *pathname, uint32_t mask)
{
info->event(pathname, mask);
}}
{
}