diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/async-teardown.c | 150 | ||||
| -rw-r--r-- | util/log.c | 9 | ||||
| -rw-r--r-- | util/meson.build | 1 |
3 files changed, 160 insertions, 0 deletions
diff --git a/util/async-teardown.c b/util/async-teardown.c new file mode 100644 index 0000000000..62bfce1b3c --- /dev/null +++ b/util/async-teardown.c @@ -0,0 +1,150 @@ +/* + * 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 <stdlib.h> +#include <stdio.h> +#include <sys/types.h> +#include <dirent.h> +#include <sys/prctl.h> +#include <signal.h> +#include <sched.h> +#include <unistd.h> + +#include "qemu/osdep.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); +} diff --git a/util/log.c b/util/log.c index d6eb0378c3..39866bdaf2 100644 --- a/util/log.c +++ b/util/log.c @@ -42,6 +42,7 @@ static QemuMutex global_mutex; static char *global_filename; static FILE *global_file; static __thread FILE *thread_file; +static __thread Notifier qemu_log_thread_cleanup_notifier; int qemu_loglevel; static bool log_append; @@ -77,6 +78,12 @@ static int log_thread_id(void) #endif } +static void qemu_log_thread_cleanup(Notifier *n, void *unused) +{ + fclose(thread_file); + thread_file = NULL; +} + /* Lock/unlock output. */ FILE *qemu_log_trylock(void) @@ -93,6 +100,8 @@ FILE *qemu_log_trylock(void) return NULL; } thread_file = logfile; + qemu_log_thread_cleanup_notifier.notify = qemu_log_thread_cleanup; + qemu_thread_atexit_add(&qemu_log_thread_cleanup_notifier); } else { rcu_read_lock(); /* diff --git a/util/meson.build b/util/meson.build index c0a7bc54d4..59c1f467bb 100644 --- a/util/meson.build +++ b/util/meson.build @@ -3,6 +3,7 @@ util_ss.add(files('thread-context.c'), numa) if not config_host_data.get('CONFIG_ATOMIC64') util_ss.add(files('atomic64.c')) endif +util_ss.add(when: 'CONFIG_LINUX', if_true: files('async-teardown.c')) util_ss.add(when: 'CONFIG_POSIX', if_true: files('aio-posix.c')) util_ss.add(when: 'CONFIG_POSIX', if_true: files('fdmon-poll.c')) if config_host_data.get('CONFIG_EPOLL_CREATE1') |