2ca10faeb8
This commit was created with scripts/clean-includes. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Juan Quintela <quintela@redhat.com> Message-Id: <20230202133830.2152150-18-armbru@redhat.com>
147 lines
3.6 KiB
C
147 lines
3.6 KiB
C
/*
|
|
* Asynchronous teardown
|
|
*
|
|
* Copyright IBM, Corp. 2022
|
|
*
|
|
* Authors:
|
|
* Claudio Imbrenda <imbrenda@linux.ibm.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2 or (at your
|
|
* option) any later version. See the COPYING file in the top-level directory.
|
|
*
|
|
*/
|
|
|
|
#include "qemu/osdep.h"
|
|
#include <dirent.h>
|
|
#include <sys/prctl.h>
|
|
#include <sched.h>
|
|
|
|
#include "qemu/async-teardown.h"
|
|
|
|
#ifdef _SC_THREAD_STACK_MIN
|
|
#define CLONE_STACK_SIZE sysconf(_SC_THREAD_STACK_MIN)
|
|
#else
|
|
#define CLONE_STACK_SIZE 16384
|
|
#endif
|
|
|
|
static pid_t the_ppid;
|
|
|
|
/*
|
|
* Close all open file descriptors.
|
|
*/
|
|
static void close_all_open_fd(void)
|
|
{
|
|
struct dirent *de;
|
|
int fd, dfd;
|
|
DIR *dir;
|
|
|
|
#ifdef CONFIG_CLOSE_RANGE
|
|
int r = close_range(0, ~0U, 0);
|
|
if (!r) {
|
|
/* Success, no need to try other ways. */
|
|
return;
|
|
}
|
|
#endif
|
|
|
|
dir = opendir("/proc/self/fd");
|
|
if (!dir) {
|
|
/* If /proc is not mounted, there is nothing that can be done. */
|
|
return;
|
|
}
|
|
/* Avoid closing the directory. */
|
|
dfd = dirfd(dir);
|
|
|
|
for (de = readdir(dir); de; de = readdir(dir)) {
|
|
fd = atoi(de->d_name);
|
|
if (fd != dfd) {
|
|
close(fd);
|
|
}
|
|
}
|
|
closedir(dir);
|
|
}
|
|
|
|
static void hup_handler(int signal)
|
|
{
|
|
/* Check every second if this process has been reparented. */
|
|
while (the_ppid == getppid()) {
|
|
/* sleep() is safe to use in a signal handler. */
|
|
sleep(1);
|
|
}
|
|
|
|
/* At this point the parent process has terminated completely. */
|
|
_exit(0);
|
|
}
|
|
|
|
static int async_teardown_fn(void *arg)
|
|
{
|
|
struct sigaction sa = { .sa_handler = hup_handler };
|
|
sigset_t hup_signal;
|
|
char name[16];
|
|
|
|
/* Set a meaningful name for this process. */
|
|
snprintf(name, 16, "cleanup/%d", the_ppid);
|
|
prctl(PR_SET_NAME, (unsigned long)name);
|
|
|
|
/*
|
|
* Close all file descriptors that might have been inherited from the
|
|
* main qemu process when doing clone, needed to make libvirt happy.
|
|
* Not using close_range for increased compatibility with older kernels.
|
|
*/
|
|
close_all_open_fd();
|
|
|
|
/* Set up a handler for SIGHUP and unblock SIGHUP. */
|
|
sigaction(SIGHUP, &sa, NULL);
|
|
sigemptyset(&hup_signal);
|
|
sigaddset(&hup_signal, SIGHUP);
|
|
sigprocmask(SIG_UNBLOCK, &hup_signal, NULL);
|
|
|
|
/* Ask to receive SIGHUP when the parent dies. */
|
|
prctl(PR_SET_PDEATHSIG, SIGHUP);
|
|
|
|
/*
|
|
* Sleep forever, unless the parent process has already terminated. The
|
|
* only interruption can come from the SIGHUP signal, which in normal
|
|
* operation is received when the parent process dies.
|
|
*/
|
|
if (the_ppid == getppid()) {
|
|
pause();
|
|
}
|
|
|
|
/* At this point the parent process has terminated completely. */
|
|
_exit(0);
|
|
}
|
|
|
|
/*
|
|
* Allocate a new stack of a reasonable size, and return a pointer to its top.
|
|
*/
|
|
static void *new_stack_for_clone(void)
|
|
{
|
|
size_t stack_size = CLONE_STACK_SIZE;
|
|
char *stack_ptr;
|
|
|
|
/* Allocate a new stack and get a pointer to its top. */
|
|
stack_ptr = qemu_alloc_stack(&stack_size);
|
|
#if !defined(HOST_HPPA)
|
|
/* The top is at the end of the area, except on HPPA. */
|
|
stack_ptr += stack_size;
|
|
#endif
|
|
|
|
return stack_ptr;
|
|
}
|
|
|
|
/*
|
|
* Block all signals, start (clone) a new process sharing the address space
|
|
* with qemu (CLONE_VM), then restore signals.
|
|
*/
|
|
void init_async_teardown(void)
|
|
{
|
|
sigset_t all_signals, old_signals;
|
|
|
|
the_ppid = getpid();
|
|
|
|
sigfillset(&all_signals);
|
|
sigprocmask(SIG_BLOCK, &all_signals, &old_signals);
|
|
clone(async_teardown_fn, new_stack_for_clone(), CLONE_VM, NULL);
|
|
sigprocmask(SIG_SETMASK, &old_signals, NULL);
|
|
}
|