mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

migration/postcopy: check PostcopyState before setting to POSTCOPY_INCOMING_RUNNING

Browse Source 
Currently, we set PostcopyState blindly to RUNNING, even we found the
previous state is not LISTENING. This will lead to a corner case.

First let's look at the code flow:

qemu_loadvm_state_main()
    ret = loadvm_process_command()
        loadvm_postcopy_handle_run()
            return -1;
    if (ret < 0) {
        if (postcopy_state_get() == POSTCOPY_INCOMING_RUNNING)
            ...
    }

>From above snippet, the corner case is loadvm_postcopy_handle_run()
always sets state to RUNNING. And then it checks the previous state. If
the previous state is not LISTENING, it will return -1. But at this
moment, PostcopyState is already been set to RUNNING.

Then ret is checked in qemu_loadvm_state_main(), when it is -1
PostcopyState is checked. Current logic would pause postcopy and retry
if PostcopyState is RUNNING. This is not what we expect, because
postcopy is not active yet.

This patch makes sure state is set to RUNNING only previous state is
LISTENING by checking the state first.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Suggested by: Peter Xu <peterx@redhat.com>
Message-Id: <20191010011316.31363-3-richardw.yang@linux.intel.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Wei Yang 2019-10-10 09:13:16 +08:00 committed by Dr. David Alan Gilbert
parent 2a7eb14844
commit 0197d89025
1 changed files with 2 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
migration/savevm.c
View File

@ -1933,7 +1933,7 @@ static void loadvm_postcopy_handle_run_bh(void *opaque)
/* After all discards we can start running and asking for pages */
static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
{
PostcopyState ps = postcopy_state_set(POSTCOPY_INCOMING_RUNNING);
PostcopyState ps = postcopy_state_get();
trace_loadvm_postcopy_handle_run();
if (ps != POSTCOPY_INCOMING_LISTENING) {
@ -1941,6 +1941,7 @@ static int loadvm_postcopy_handle_run(MigrationIncomingState *mis)
return -1;
}
postcopy_state_set(POSTCOPY_INCOMING_RUNNING);
mis->bh = qemu_bh_new(loadvm_postcopy_handle_run_bh, mis);
qemu_bh_schedule(mis->bh);