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libc: update status for component select handlers

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In case of contexts blocked in select() the monitor updates the
file-descriptor status, but if the entrypoint is just blocked for the
select handler, the status must be updated explicitly on
dispatch_select().
This commit is contained in:
Christian Helmuth 2020-09-28 16:14:24 +02:00
parent bbb017dc24
commit 26011a7151
3 changed files with 54 additions and 40 deletions
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1
repos/libports/lib/symbols/libc
View File

@ -418,7 +418,6 @@ lcong48 T
ldexp T
ldiv T
lfind T
libc_select_notify V
link W
listen T
llabs T

5
repos/libports/src/lib/libc/select.cc
View File

@ -63,9 +63,6 @@ void Libc::init_select(Select &select, Signal &signal, Monitor &monitor)
}
void (*libc_select_notify)() __attribute__((weak));
/** Description for a task waiting in select */
struct Libc::Select_cb
{
@ -416,6 +413,8 @@ int Libc::Select_handler_base::select(int nfds, fd_set &readfds,
void Libc::Select_handler_base::dispatch_select()
{
Libc::select_notify_from_kernel();
Select_handler_cb &select_cb = *_select_cb;
if (select_cb->nready == 0) return;

88
repos/libports/src/test/libc_component/main.cc
View File

@ -53,7 +53,7 @@ static void use_file_system()
{
int result = 0;
int const fd = open("/tmp/blub", O_RDWR | O_NONBLOCK | O_CREAT | O_APPEND);
int const fd = open("/tmp/blub", O_RDWR /*| O_NONBLOCK*/ | O_CREAT | O_APPEND);
if (fd == -1) die("open");
printf("open returned fd %d\n", fd);
@ -96,41 +96,6 @@ struct Log::Session_component : Genode::Rpc_object<Log_session>
fd_set _exceptfds;
bool _in_read = false;
void _select()
{
int nready = 0;
do {
fd_set readfds = _readfds;
fd_set writefds = _writefds;
fd_set exceptfds = _exceptfds;
nready = _select_handler.select(_fd + 1, readfds, writefds, exceptfds);
if (nready)
_select_ready(nready, readfds, writefds, exceptfds);
} while (nready);
}
Libc::Select_handler<Session_component> _select_handler {
*this, &Session_component::_select_ready };
void _read()
{
_in_read = true;
/* never mind the potentially nested with_libc */
Libc::with_libc([&] () {
int const result = read(_fd, _buf, sizeof(_buf)-1);
if (result <= 0) {
Genode::warning("read returned ", result, " in select handler");
return;
}
_buf[result] = 0;
Genode::log("read from file \"", Genode::Cstring(_buf), "\"");
});
_in_read = false;
}
void _select_ready(int nready, fd_set const &readfds, fd_set const &writefds, fd_set const &exceptfds)
{
Libc::with_libc([&] () {
@ -154,6 +119,55 @@ struct Log::Session_component : Genode::Rpc_object<Log_session>
});
}
void _select()
{
/*
* This function activates the select handler. Ready file FDs must be
* handled immediately on return from select() as these events will not
* unblock the entrypoint later on.
*/
int nready = 0;
do {
fd_set readfds = _readfds;
fd_set writefds = _writefds;
fd_set exceptfds = _exceptfds;
nready = _select_handler.select(_fd + 1, readfds, writefds, exceptfds);
if (nready)
_select_ready(nready, readfds, writefds, exceptfds);
} while (nready);
}
Libc::Select_handler<Session_component> _select_handler {
*this, &Session_component::_handle_select };
void _handle_select(int nready, fd_set const &readfds, fd_set const &writefds, fd_set const &exceptfds)
{
/* handle all ready fds */
_select_ready(nready, readfds, writefds, exceptfds);
/* reactivate select handler */
_select();
}
void _read()
{
_in_read = true;
/* never mind the potentially nested with_libc */
Libc::with_libc([&] () {
int const result = read(_fd, _buf, sizeof(_buf)-1);
if (result <= 0) {
Genode::warning("read returned ", result, " in select handler");
return;
}
_buf[result] = 0;
Genode::log("read from file \"", Genode::Cstring(_buf), "\"");
});
_in_read = false;
}
Session_component(Libc::Env &env) : _env(env)
{
Libc::with_libc([&] () {
@ -171,6 +185,8 @@ struct Log::Session_component : Genode::Rpc_object<Log_session>
/* initially call read two times to ensure blocking */
_read(); _read();
_select();
}
void write(String const &string_buf) override