From 19d7219176df65a532a2e99f304a457ceb6986ae Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Tue, 14 Feb 2012 11:14:38 +0100 Subject: [PATCH 73/99] async: Allow nested qemu_bh_poll calls RH-Author: Kevin Wolf Message-id: <1329218101-24213-74-git-send-email-kwolf@redhat.com> Patchwork-id: 37270 O-Subject: [RHEL-6.3 qemu-kvm PATCH v2 73/96] async: Allow nested qemu_bh_poll calls Bugzilla: 783950 RH-Acked-by: Paolo Bonzini RH-Acked-by: Marcelo Tosatti RH-Acked-by: Laszlo Ersek Bugzilla: 783950 qemu may segfault when a BH handler first deletes a BH and then (possibly indirectly) calls a nested qemu_bh_poll(). This is because the inner instance frees the BH and deletes it from the list that the outer one processes. This patch deletes BHs only in the outermost qemu_bh_poll instance. Commit 7887f620 already tried to achieve the same, but it assumed that the BH handler would only delete its own BH. With a nested qemu_bh_poll(), this isn't guaranteed, so that commit wasn't enough. Hope this one fixes it for real. Signed-off-by: Kevin Wolf (cherry picked from commit 648fb0ea5e9d7f32c80ec23c3ece4321403dfecd) Conflicts: async.c Signed-off-by: Kevin Wolf --- async.c | 24 ++++++++++++++++-------- 1 files changed, 16 insertions(+), 8 deletions(-) Signed-off-by: Michal Novotny --- async.c | 24 ++++++++++++++++-------- 1 files changed, 16 insertions(+), 8 deletions(-) diff --git a/async.c b/async.c index 3fe70b9..a8b4ef6 100644 --- a/async.c +++ b/async.c @@ -55,6 +55,9 @@ int qemu_bh_poll(void) { QEMUBH *bh, **bhp, *next; int ret; + static int nesting = 0; + + nesting++; ret = 0; for (bh = first_bh; bh; bh = next) { @@ -68,15 +71,20 @@ int qemu_bh_poll(void) } } + nesting--; + /* remove deleted bhs */ - bhp = &first_bh; - while (*bhp) { - bh = *bhp; - if (bh->deleted) { - *bhp = bh->next; - qemu_free(bh); - } else - bhp = &bh->next; + if (!nesting) { + bhp = &first_bh; + while (*bhp) { + bh = *bhp; + if (bh->deleted) { + *bhp = bh->next; + g_free(bh); + } else { + bhp = &bh->next; + } + } } return ret; -- 1.7.7.5