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lib: Implement the criu_restore_child() call v2

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It fully uses the swrk action of criu. The problems, that caller may
have is that the restored tasks die _before_ libcriu's call returns.

v2:
* rename _sub to _child
* unblock sigchild before execl-ing criu

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Pavel Emelyanov
2014-06-17 21:10:46 +04:00
parent b6f6426bef
commit 24d2f56fad
2 changed files with 82 additions and 0 deletions
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81
lib/criu.c
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@@ -1,4 +1,7 @@
#include "version.h"
#include <sys/prctl.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <limits.h>
@@ -6,6 +9,7 @@
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <signal.h>
#include "criu.h"
#include "rpc.pb-c.h"
@@ -450,3 +454,80 @@ exit:
return ret;
}
int criu_restore_child(void)
{
int sks[2], pid, ret = -1;
CriuReq req = CRIU_REQ__INIT;
CriuResp *resp = NULL;
if (socketpair(PF_LOCAL, SOCK_SEQPACKET, 0, sks))
goto out;
/*
* Set us as child subreaper so that after the swrk
* finishes restore and exits the restored subtree
* gets reparented to us.
*/
if (prctl(PR_SET_CHILD_SUBREAPER, 1, 0, 0))
goto err;
pid = fork();
if (pid < 0)
goto err;
if (pid == 0) {
sigset_t mask;
char fds[11];
/*
* Unblock SIGCHLD.
*
* The caller of this function is supposed to have
* this signal blocked. Otherwise it risks to get
* into situation, when this routine is not yet
* returned, but the restore subtree exits and
* emits the SIGCHLD.
*
* In turn, unblocked SIGCHLD is required to make
* criu restoration process work -- it catches
* subtasks restore errors in this handler.
*/
sigemptyset(&mask);
sigaddset(&mask, SIGCHLD);
sigprocmask(SIG_UNBLOCK, &mask, NULL);
close(sks[0]);
sprintf(fds, "%d", sks[1]);
execlp("criu", "criu", "swrk", fds, NULL);
exit(1);
}
close(sks[1]);
req.type = CRIU_REQ_TYPE__RESTORE;
req.opts = opts;
ret = send_req_and_recv_resp_sk(sks[0], &req, &resp);
close(sks[0]);
waitpid(pid, NULL, 0);
/* Drop the subreaper role _after_ swrk exits */
prctl(PR_SET_CHILD_SUBREAPER, 0, 0, 0);
if (!ret) {
ret = resp->success ? resp->restore->pid : -EBADE;
criu_resp__free_unpacked(resp, NULL);
}
out:
return ret;
err:
close(sks[1]);
close(sks[0]);
goto out;
}