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648fb0ea5e
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 <kwolf@redhat.com>
142 lines
3.4 KiB
C
142 lines
3.4 KiB
C
/*
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* QEMU System Emulator
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*
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* Copyright (c) 2003-2008 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu-common.h"
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#include "qemu-aio.h"
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/* Anchor of the list of Bottom Halves belonging to the context */
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static struct QEMUBH *first_bh;
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/***********************************************************/
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/* bottom halves (can be seen as timers which expire ASAP) */
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struct QEMUBH {
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QEMUBHFunc *cb;
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void *opaque;
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int scheduled;
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int idle;
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int deleted;
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QEMUBH *next;
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};
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QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
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{
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QEMUBH *bh;
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bh = g_malloc0(sizeof(QEMUBH));
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bh->cb = cb;
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bh->opaque = opaque;
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bh->next = first_bh;
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first_bh = bh;
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return bh;
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}
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int qemu_bh_poll(void)
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{
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QEMUBH *bh, **bhp, *next;
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int ret;
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static int nesting = 0;
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nesting++;
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ret = 0;
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for (bh = first_bh; bh; bh = next) {
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next = bh->next;
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if (!bh->deleted && bh->scheduled) {
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bh->scheduled = 0;
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if (!bh->idle)
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ret = 1;
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bh->idle = 0;
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bh->cb(bh->opaque);
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}
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}
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nesting--;
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/* remove deleted bhs */
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if (!nesting) {
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bhp = &first_bh;
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while (*bhp) {
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bh = *bhp;
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if (bh->deleted) {
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*bhp = bh->next;
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g_free(bh);
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} else {
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bhp = &bh->next;
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}
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}
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}
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return ret;
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}
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void qemu_bh_schedule_idle(QEMUBH *bh)
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{
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if (bh->scheduled)
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return;
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bh->scheduled = 1;
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bh->idle = 1;
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}
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void qemu_bh_schedule(QEMUBH *bh)
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{
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if (bh->scheduled)
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return;
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bh->scheduled = 1;
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bh->idle = 0;
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/* stop the currently executing CPU to execute the BH ASAP */
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qemu_notify_event();
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}
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void qemu_bh_cancel(QEMUBH *bh)
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{
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bh->scheduled = 0;
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}
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void qemu_bh_delete(QEMUBH *bh)
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{
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bh->scheduled = 0;
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bh->deleted = 1;
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}
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void qemu_bh_update_timeout(int *timeout)
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{
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QEMUBH *bh;
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for (bh = first_bh; bh; bh = bh->next) {
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if (!bh->deleted && bh->scheduled) {
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if (bh->idle) {
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/* idle bottom halves will be polled at least
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* every 10ms */
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*timeout = MIN(10, *timeout);
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} else {
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/* non-idle bottom halves will be executed
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* immediately */
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*timeout = 0;
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break;
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}
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}
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}
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}
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