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The following segfault is encountered if the NBD server closes the UNIX domain socket immediately after negotiation: Program terminated with signal SIGSEGV, Segmentation fault. #0 aio_co_schedule (ctx=0x0, co=0xd3c0ff2ef0) at util/async.c:441 441 QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines, (gdb) bt #0 0x000000d3c01a50f8 in aio_co_schedule (ctx=0x0, co=0xd3c0ff2ef0) at util/async.c:441 #1 0x000000d3c012fa90 in nbd_coroutine_end (bs=bs@entry=0xd3c0fec650, request=<optimized out>) at block/nbd-client.c:207 #2 0x000000d3c012fb58 in nbd_client_co_preadv (bs=0xd3c0fec650, offset=0, bytes=<optimized out>, qiov=0x7ffc10a91b20, flags=0) at block/nbd-client.c:237 #3 0x000000d3c0128e63 in bdrv_driver_preadv (bs=bs@entry=0xd3c0fec650, offset=offset@entry=0, bytes=bytes@entry=512, qiov=qiov@entry=0x7ffc10a91b20, flags=0) at block/io.c:836 #4 0x000000d3c012c3e0 in bdrv_aligned_preadv (child=child@entry=0xd3c0ff51d0, req=req@entry=0x7f31885d6e90, offset=offset@entry=0, bytes=bytes@entry=512, align=align@entry=1, qiov=qiov@entry=0x7ffc10a91b20, f +lags=0) at block/io.c:1086 #5 0x000000d3c012c6b8 in bdrv_co_preadv (child=0xd3c0ff51d0, offset=offset@entry=0, bytes=bytes@entry=512, qiov=qiov@entry=0x7ffc10a91b20, flags=flags@entry=0) at block/io.c:1182 #6 0x000000d3c011cc17 in blk_co_preadv (blk=0xd3c0ff4f80, offset=0, bytes=512, qiov=0x7ffc10a91b20, flags=0) at block/block-backend.c:1032 #7 0x000000d3c011ccec in blk_read_entry (opaque=0x7ffc10a91b40) at block/block-backend.c:1079 #8 0x000000d3c01bbb96 in coroutine_trampoline (i0=<optimized out>, i1=<optimized out>) at util/coroutine-ucontext.c:79 #9 0x00007f3196cb8600 in __start_context () at /lib64/libc.so.6 The problem is that nbd_client_init() uses nbd_client_attach_aio_context() -> aio_co_schedule(new_context, client->read_reply_co). Execution of read_reply_co is deferred to a BH which doesn't run until later. In the mean time blk_co_preadv() can be called and nbd_coroutine_end() calls aio_wake() on read_reply_co. At this point in time read_reply_co's ctx isn't set because it has never been entered yet. This patch simplifies the nbd_co_send_request() -> nbd_co_receive_reply() -> nbd_coroutine_end() lifecycle to just nbd_co_send_request() -> nbd_co_receive_reply(). The request is "ended" if an error occurs at any point. Callers no longer have to invoke nbd_coroutine_end(). This cleanup also eliminates the segfault because we don't call aio_co_schedule() to wake up s->read_reply_co if sending the request failed. It is only necessary to wake up s->read_reply_co if a reply was received. Note this only happens with UNIX domain sockets on Linux. It doesn't seem possible to reproduce this with TCP sockets. Suggested-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20170829122745.14309-2-stefanha@redhat.com> Signed-off-by: Eric Blake <eblake@redhat.com> |
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| .. | ||
| accounting.c | ||
| backup.c | ||
| blkdebug.c | ||
| blkreplay.c | ||
| blkverify.c | ||
| block-backend.c | ||
| bochs.c | ||
| cloop.c | ||
| commit.c | ||
| crypto.c | ||
| crypto.h | ||
| curl.c | ||
| dirty-bitmap.c | ||
| dmg-bz2.c | ||
| dmg.c | ||
| dmg.h | ||
| file-posix.c | ||
| file-win32.c | ||
| gluster.c | ||
| io.c | ||
| iscsi-opts.c | ||
| iscsi.c | ||
| linux-aio.c | ||
| Makefile.objs | ||
| mirror.c | ||
| nbd-client.c | ||
| nbd-client.h | ||
| nbd.c | ||
| nfs.c | ||
| null.c | ||
| parallels.c | ||
| qapi.c | ||
| qcow2-bitmap.c | ||
| qcow2-cache.c | ||
| qcow2-cluster.c | ||
| qcow2-refcount.c | ||
| qcow2-snapshot.c | ||
| qcow2.c | ||
| qcow2.h | ||
| qcow.c | ||
| qed-check.c | ||
| qed-cluster.c | ||
| qed-l2-cache.c | ||
| qed-table.c | ||
| qed.c | ||
| qed.h | ||
| quorum.c | ||
| raw-format.c | ||
| rbd.c | ||
| replication.c | ||
| sheepdog.c | ||
| snapshot.c | ||
| ssh.c | ||
| stream.c | ||
| throttle-groups.c | ||
| trace-events | ||
| vdi.c | ||
| vhdx-endian.c | ||
| vhdx-log.c | ||
| vhdx.c | ||
| vhdx.h | ||
| vmdk.c | ||
| vpc.c | ||
| vvfat.c | ||
| vxhs.c | ||
| win32-aio.c | ||
| write-threshold.c | ||