On Tue, Jan 25, 2011 at 10:13 AM, Corentin Chary <corentin.ch...@gmail.com> wrote: > On Tue, Jan 25, 2011 at 10:03 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: >> On Tue, Jan 25, 2011 at 8:33 AM, Corentin Chary >> <corentin.ch...@gmail.com> wrote: >>> From: Yoshiaki Tamura <tamura.yoshi...@lab.ntt.co.jp> >>> >>> Currently qemu_set_fd_handler2() is only setting ioh->deleted upon >>> deleting. This may cause a crash when a read handler calls >>> qemu_set_fd_handler2() to delete handlers, but a write handler is >>> still invoked from main_loop_wait(). Because main_loop_wait() checks >>> handlers before calling, setting NULL upon deleting will protect >>> handlers being called if already deleted. >>> >>> One example is the new threaded vnc server. When an error occurs in >>> the context of a read handler, it'll releases resources and deletes >>> handlers. However, because the write handler still exists, it'll be >>> called, and then crashes because of lack of resources. This patch >>> fixes it. >> >> Does this case still happen with qemu.git/master? In November I sent >> a patch to check for deleted handlers: >> >> commit 0290b57bdfec83ca78b6d119ea9847bb17943328 >> Author: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com> >> Date: Wed Nov 3 14:29:44 2010 +0000 >> >> Delete IOHandlers after potentially running them >> >> Since commit 4bed9837309e58d208183f81d8344996744292cf an .fd_read() >> handler that deletes its IOHandler is exposed to .fd_write() being >> called on the deleted IOHandler. >> >> This patch fixes deletion so that .fd_read() and .fd_write() are never >> called on an IOHandler that is marked for deletion. >> >> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com> >> Signed-off-by: Anthony Liguori <aligu...@us.ibm.com> >> >> So I don't think Yoshi's patch is necessary anymore? > > Ho I didn't see that one. > It's probably not necessary, but it stills make sense to apply this > patch since there is > absolutly no reasons to keep the old value in fd_read and fd_write when > the user explicitly asked to set them to NULL.
That's true, I don't see a good reason why we shouldn't clear them. The only minor advantage to keeping them is that it helps when debugging QEMU - you can identify the fd handler by its fd_read/fd_write function pointers easily. Stefan
