Re: [Qemu-devel] [PATCH 7/9] iohandler: associate with main event loop via a QSource

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

于 2013-5-6 15:53, Paolo Bonzini 写道:
> Il 03/05/2013 18:03, Michael Roth ha scritto:
>> This introduces a GlibQContext wrapper around the main GMainContext
>> event loop, and associates iohandlers with it via a QSource (which
>> GlibQContext creates a GSource from so that it can be driven via
>> GLib. A subsequent patch will drive the GlibQContext directly)
>>
>> We also add "QContext-aware" functionality to iohandler interfaces
>> so that they can be bound to other QContext event loops, and add
>> non-global set_fd_handler() interfaces to facilitate this. This is made
>> possible by simply searching a given QContext for a QSource by the name
>> of "iohandler" so that we can attach event handlers to the associated
>> IOHandlerState.
>>
>> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
>
> This patch is why I think that this is a bit overengineered.  The main
> loop is always glib-based, there should be no need to go through the
> QSource abstraction.
>
   I thought to use glib-based eventloop before, but found that
AioContext's pending request need to be flushed in release
operation, which can't be done in g_main_context_release. This
brings difficult to do every thing based on glib's API. Do
you think we should stick to QContext to wrap or hide GMainContext?

> BTW, this is broken for Win32.  The right thing to do here is to first
> convert iohandler to a GSource in such a way that it works for both
> POSIX and Win32, and then (if needed) we can later convert GSource to
> QSource.
>
> Paolo
>
>> ---
>>   include/qemu/main-loop.h |   31 +++++-
>>   iohandler.c              |  238 ++++++++++++++++++++++++++++++++--------------
>>   main-loop.c              |   21 +++-
>>   3 files changed, 213 insertions(+), 77 deletions(-)
>>
>> diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
>> index 6f0200a..dbadf9f 100644
>> --- a/include/qemu/main-loop.h
>> +++ b/include/qemu/main-loop.h
>> @@ -26,6 +26,7 @@
>>   #define QEMU_MAIN_LOOP_H 1
>>
>>   #include "block/aio.h"
>> +#include "qcontext/qcontext.h"
>>
>>   #define SIG_IPI SIGUSR1
>>
>> @@ -168,9 +169,24 @@ void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
>>
>>   /* async I/O support */
>>
>> +#define QSOURCE_IOHANDLER "iohandler"
>> +
>>   typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
>>   typedef int IOCanReadHandler(void *opaque);
>>
>> +QContext *qemu_get_qcontext(void);
>> +/**
>> + * iohandler_attach: Attach a QSource to a QContext
>> + *
>> + * This enables the use of IOHandler interfaces such as
>> + * set_fd_handler() on the given QContext. IOHandler lists will be
>> + * tracked/handled/dispatched based on a named QSource that is added to
>> + * the QContext
>> + *
>> + * @ctx: A QContext to add an IOHandler QSource to
>> + */
>> +void iohandler_attach(QContext *ctx);
>> +
>>   /**
>>    * qemu_set_fd_handler2: Register a file descriptor with the main loop
>>    *
>> @@ -217,6 +233,13 @@ int qemu_set_fd_handler2(int fd,
>>                            IOHandler *fd_write,
>>                            void *opaque);
>>
>> +int set_fd_handler2(QContext *ctx,
>> +                    int fd,
>> +                    IOCanReadHandler *fd_read_poll,
>> +                    IOHandler *fd_read,
>> +                    IOHandler *fd_write,
>> +                    void *opaque);
>> +
>>   /**
>>    * qemu_set_fd_handler: Register a file descriptor with the main loop
>>    *
>> @@ -250,6 +273,12 @@ int qemu_set_fd_handler(int fd,
>>                           IOHandler *fd_write,
>>                           void *opaque);
>>
>> +int set_fd_handler(QContext *ctx,
>> +                   int fd,
>> +                   IOHandler *fd_read,
>> +                   IOHandler *fd_write,
>> +                   void *opaque);
>> +
>>   #ifdef CONFIG_POSIX
>>   /**
>>    * qemu_add_child_watch: Register a child process for reaping.
>> @@ -302,8 +331,6 @@ void qemu_mutex_unlock_iothread(void);
>>   /* internal interfaces */
>>
>>   void qemu_fd_register(int fd);
>> -void qemu_iohandler_fill(GArray *pollfds);
>> -void qemu_iohandler_poll(GArray *pollfds, int rc);
>>
>>   QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
>>   void qemu_bh_schedule_idle(QEMUBH *bh);
>> diff --git a/iohandler.c b/iohandler.c
>> index ae2ef8f..8625272 100644
>> --- a/iohandler.c
>> +++ b/iohandler.c
>> @@ -41,38 +41,170 @@ typedef struct IOHandlerRecord {
>>       int fd;
>>       int pollfds_idx;
>>       bool deleted;
>> +    GPollFD pfd;
>> +    bool pfd_added;
>>   } IOHandlerRecord;
>>
>> -static QLIST_HEAD(, IOHandlerRecord) io_handlers =
>> -    QLIST_HEAD_INITIALIZER(io_handlers);
>> +typedef struct IOHandlerState {
>> +    QLIST_HEAD(, IOHandlerRecord) io_handlers;
>> +} IOHandlerState;
>>
>> +static bool iohandler_prepare(QSource *qsource, int *timeout)
>> +{
>> +    QSourceClass *qsourcek = QSOURCE_GET_CLASS(qsource);
>> +    IOHandlerState *s = qsourcek->get_user_data(qsource);
>> +    IOHandlerRecord *ioh;
>>
>> -/* XXX: fd_read_poll should be suppressed, but an API change is
>> -   necessary in the character devices to suppress fd_can_read(). */
>> -int qemu_set_fd_handler2(int fd,
>> -                         IOCanReadHandler *fd_read_poll,
>> -                         IOHandler *fd_read,
>> -                         IOHandler *fd_write,
>> -                         void *opaque)
>> +    QLIST_FOREACH(ioh, &s->io_handlers, next) {
>> +        int events = 0;
>> +
>> +        if (ioh->deleted)
>> +            continue;
>> +
>> +        if (ioh->fd_read &&
>> +            (!ioh->fd_read_poll ||
>> +             ioh->fd_read_poll(ioh->opaque) != 0)) {
>> +            events |= G_IO_IN | G_IO_HUP | G_IO_ERR;
>> +        }
>> +        if (ioh->fd_write) {
>> +            events |= G_IO_OUT | G_IO_ERR;
>> +        }
>> +        if (events) {
>> +            ioh->pfd.fd = ioh->fd;
>> +            ioh->pfd.events = events;
>> +            if (!ioh->pfd_added) {
>> +                qsourcek->add_poll(qsource, &ioh->pfd);
>> +                ioh->pfd_added = true;
>> +            }
>> +        } else {
>> +            ioh->pfd.events = 0;
>> +            ioh->pfd.revents = 0;
>> +        }
>> +    }
>> +    *timeout = 10;
>> +    return false;
>> +}
>> +
>> +static bool iohandler_check(QSource *qsource)
>>   {
>> +    QSourceClass *sourcek = QSOURCE_GET_CLASS(qsource);
>> +    IOHandlerState *s = sourcek->get_user_data(qsource);
>>       IOHandlerRecord *ioh;
>>
>> +    QLIST_FOREACH(ioh, &s->io_handlers, next) {
>> +        if (ioh->deleted) {
>> +            continue;
>> +        }
>> +        if (ioh->pfd.revents) {
>> +            return true;
>> +        }
>> +    }
>> +
>> +    return false;
>> +}
>> +
>> +static bool iohandler_dispatch(QSource *qsource)
>> +{
>> +    QSourceClass *sourcek = QSOURCE_GET_CLASS(qsource);
>> +    IOHandlerState *s = sourcek->get_user_data(qsource);
>> +    IOHandlerRecord *pioh, *ioh;
>> +
>> +    QLIST_FOREACH_SAFE(ioh, &s->io_handlers, next, pioh) {
>> +        int revents = ioh->pfd.revents;
>> +        if (!ioh->deleted && ioh->fd_read &&
>> +            (revents && (G_IO_IN | G_IO_HUP | G_IO_ERR))) {
>> +            ioh->fd_read(ioh->opaque);
>> +        }
>> +
>> +        if (!ioh->deleted && ioh->fd_write &&
>> +            (revents & (G_IO_OUT | G_IO_ERR))) {
>> +            ioh->fd_write(ioh->opaque);
>> +        }
>> +
>> +        /* Do this last in case read/write handlers marked it for deletion */
>> +        if (ioh->deleted) {
>> +            if (ioh->pfd_added) {
>> +                sourcek->remove_poll(qsource, &ioh->pfd);
>> +            }
>> +            QLIST_REMOVE(ioh, next);
>> +            g_free(ioh);
>> +        }
>> +    }
>> +
>> +    return true;
>> +}
>> +
>> +static void iohandler_finalize(QSource *qsource)
>> +{
>> +    QSourceClass *sourcek = QSOURCE_GET_CLASS(qsource);
>> +    IOHandlerState *s = sourcek->get_user_data(qsource);
>> +    IOHandlerRecord *pioh, *ioh;
>> +
>> +    QLIST_FOREACH_SAFE(ioh, &s->io_handlers, next, pioh) {
>> +        if (ioh->pfd_added) {
>> +            sourcek->remove_poll(qsource, &ioh->pfd);
>> +        }
>> +        QLIST_REMOVE(ioh, next);
>> +        g_free(ioh);
>> +    }
>> +
>> +    g_free(s);
>> +}
>> +
>> +static const QSourceFuncs iohandler_funcs = {
>> +    iohandler_prepare,
>> +    iohandler_check,
>> +    iohandler_dispatch,
>> +    iohandler_finalize,
>> +};
>> +
>> +void iohandler_attach(QContext *ctx)
>> +{
>> +    IOHandlerState *s;
>> +    QSource *qsource;
>> +
>> +    s = g_new0(IOHandlerState, 1);
>> +    QLIST_INIT(&s->io_handlers);
>> +
>> +    qsource = qsource_new(iohandler_funcs, NULL, QSOURCE_IOHANDLER, s);
>> +    qcontext_attach(ctx, qsource, NULL);
>> +}
>> +
>> +int set_fd_handler2(QContext *ctx,
>> +                    int fd,
>> +                    IOCanReadHandler *fd_read_poll,
>> +                    IOHandler *fd_read,
>> +                    IOHandler *fd_write,
>> +                    void *opaque)
>> +{
>> +    QSourceClass *sourcek;
>> +    QSource *source;
>> +    IOHandlerState *s;
>> +    IOHandlerRecord *ioh;
>> +
>> +    source = qcontext_find_source_by_name(ctx, QSOURCE_IOHANDLER);
>> +    if (!source) {
>> +        assert(0);
>> +    }
>> +    sourcek = QSOURCE_GET_CLASS(source);
>> +    s = sourcek->get_user_data(source);
>> +
>>       assert(fd >= 0);
>>
>>       if (!fd_read && !fd_write) {
>> -        QLIST_FOREACH(ioh, &io_handlers, next) {
>> +        QLIST_FOREACH(ioh, &s->io_handlers, next) {
>>               if (ioh->fd == fd) {
>>                   ioh->deleted = 1;
>>                   break;
>>               }
>>           }
>>       } else {
>> -        QLIST_FOREACH(ioh, &io_handlers, next) {
>> +        QLIST_FOREACH(ioh, &s->io_handlers, next) {
>>               if (ioh->fd == fd)
>>                   goto found;
>>           }
>>           ioh = g_malloc0(sizeof(IOHandlerRecord));
>> -        QLIST_INSERT_HEAD(&io_handlers, ioh, next);
>> +        QLIST_INSERT_HEAD(&s->io_handlers, ioh, next);
>>       found:
>>           ioh->fd = fd;
>>           ioh->fd_read_poll = fd_read_poll;
>> @@ -86,74 +218,34 @@ int qemu_set_fd_handler2(int fd,
>>       return 0;
>>   }
>>
>> -int qemu_set_fd_handler(int fd,
>> -                        IOHandler *fd_read,
>> -                        IOHandler *fd_write,
>> -                        void *opaque)
>> +int set_fd_handler(QContext *ctx,
>> +                   int fd,
>> +                   IOHandler *fd_read,
>> +                   IOHandler *fd_write,
>> +                   void *opaque)
>>   {
>> -    return qemu_set_fd_handler2(fd, NULL, fd_read, fd_write, opaque);
>> +    return set_fd_handler2(ctx, fd, NULL, fd_read, fd_write, opaque);
>>   }
>>
>> -void qemu_iohandler_fill(GArray *pollfds)
>> +/* XXX: fd_read_poll should be suppressed, but an API change is
>> +   necessary in the character devices to suppress fd_can_read(). */
>> +int qemu_set_fd_handler2(int fd,
>> +                         IOCanReadHandler *fd_read_poll,
>> +                         IOHandler *fd_read,
>> +                         IOHandler *fd_write,
>> +                         void *opaque)
>>   {
>> -    IOHandlerRecord *ioh;
>> -
>> -    QLIST_FOREACH(ioh, &io_handlers, next) {
>> -        int events = 0;
>> -
>> -        if (ioh->deleted)
>> -            continue;
>> -        if (ioh->fd_read &&
>> -            (!ioh->fd_read_poll ||
>> -             ioh->fd_read_poll(ioh->opaque) != 0)) {
>> -            events |= G_IO_IN | G_IO_HUP | G_IO_ERR;
>> -        }
>> -        if (ioh->fd_write) {
>> -            events |= G_IO_OUT | G_IO_ERR;
>> -        }
>> -        if (events) {
>> -            GPollFD pfd = {
>> -                .fd = ioh->fd,
>> -                .events = events,
>> -            };
>> -            ioh->pollfds_idx = pollfds->len;
>> -            g_array_append_val(pollfds, pfd);
>> -        } else {
>> -            ioh->pollfds_idx = -1;
>> -        }
>> -    }
>> +    return set_fd_handler2(qemu_get_qcontext(), fd,
>> +                           fd_read_poll, fd_read, fd_write,
>> +                           opaque);
>>   }
>>
>> -void qemu_iohandler_poll(GArray *pollfds, int ret)
>> +int qemu_set_fd_handler(int fd,
>> +                        IOHandler *fd_read,
>> +                        IOHandler *fd_write,
>> +                        void *opaque)
>>   {
>> -    if (ret > 0) {
>> -        IOHandlerRecord *pioh, *ioh;
>> -
>> -        QLIST_FOREACH_SAFE(ioh, &io_handlers, next, pioh) {
>> -            int revents = 0;
>> -
>> -            if (!ioh->deleted && ioh->pollfds_idx != -1) {
>> -                GPollFD *pfd = &g_array_index(pollfds, GPollFD,
>> -                                              ioh->pollfds_idx);
>> -                revents = pfd->revents;
>> -            }
>> -
>> -            if (!ioh->deleted && ioh->fd_read &&
>> -                (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR))) {
>> -                ioh->fd_read(ioh->opaque);
>> -            }
>> -            if (!ioh->deleted && ioh->fd_write &&
>> -                (revents & (G_IO_OUT | G_IO_ERR))) {
>> -                ioh->fd_write(ioh->opaque);
>> -            }
>> -
>> -            /* Do this last in case read/write handlers marked it for deletion */
>> -            if (ioh->deleted) {
>> -                QLIST_REMOVE(ioh, next);
>> -                g_free(ioh);
>> -            }
>> -        }
>> -    }
>> +    return qemu_set_fd_handler2(fd, NULL, fd_read, fd_write, opaque);
>>   }
>>
>>   /* reaping of zombies.  right now we're not passing the status to
>> diff --git a/main-loop.c b/main-loop.c
>> index f46aece..ae284a6 100644
>> --- a/main-loop.c
>> +++ b/main-loop.c
>> @@ -27,6 +27,8 @@
>>   #include "slirp/slirp.h"
>>   #include "qemu/main-loop.h"
>>   #include "block/aio.h"
>> +#include "qcontext/qcontext.h"
>> +#include "qcontext/glib-qcontext.h"
>>
>>   #ifndef _WIN32
>>
>> @@ -107,6 +109,13 @@ static int qemu_signal_init(void)
>>   }
>>   #endif
>>
>> +static QContext *qemu_qcontext;
>> +
>> +QContext *qemu_get_qcontext(void)
>> +{
>> +    return qemu_qcontext;
>> +}
>> +
>>   static AioContext *qemu_aio_context;
>>
>>   AioContext *qemu_get_aio_context(void)
>> @@ -128,6 +137,7 @@ int qemu_init_main_loop(void)
>>   {
>>       int ret;
>>       GSource *src;
>> +    Error *err = NULL;
>>
>>       init_clocks();
>>       if (init_timer_alarm() < 0) {
>> @@ -135,6 +145,15 @@ int qemu_init_main_loop(void)
>>           exit(1);
>>       }
>>
>> +    qemu_qcontext = QCONTEXT(glib_qcontext_new("main", false, &err));
>> +    if (err) {
>> +        g_warning("error initializing main qcontext");
>> +        error_free(err);
>> +        return -1;
>> +    }
>> +
>> +    iohandler_attach(qemu_qcontext);
>> +
>>       ret = qemu_signal_init();
>>       if (ret) {
>>           return ret;
>> @@ -464,9 +483,7 @@ int main_loop_wait(int nonblocking)
>>       slirp_update_timeout(&timeout);
>>       slirp_pollfds_fill(gpollfds);
>>   #endif
>> -    qemu_iohandler_fill(gpollfds);
>>       ret = os_host_main_loop_wait(timeout);
>> -    qemu_iohandler_poll(gpollfds, ret);
>>   #ifdef CONFIG_SLIRP
>>       slirp_pollfds_poll(gpollfds, (ret < 0));
>>   #endif
>>
>
>


-- 
Best Regards

Wenchao Xia