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


From: mdroth
Subject: Re: [Qemu-devel] [PATCH 7/9] iohandler: associate with main event loop via a QSource
Date: Mon, 6 May 2013 14:03:24 -0500
User-agent: Mutt/1.5.21 (2010-09-15)

On Mon, May 06, 2013 at 09:53:12AM +0200, Paolo Bonzini wrote:
> 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 <address@hidden>
> 
> 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.
> 
> 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.

Yup, forgot to note that Win32 was broken and on my TODO. I'll work on
that and stick to using GSources for now.

> 
> 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
> > 
> 



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