[CRIU] [PATCH v3 45/55] ns: Add usernsd signal handler

[Andrei Vagin]

On Tue, Apr 25, 2017 at 03:14:33PM +0300, Kirill Tkhai wrote:
> 
> On 25.04.2017 08:34, Andrei Vagin wrote:
> > Could you explain in each commit message why we need these changes and
> > what they do?
> 
> ns: Add usernsd signal handler
> 
> Handler to catch exited children of usernsd.
> This will be used in next patches to watch
> for pid_ns helpers exit.
> 
> v3: pr_err() -> pr_info()
> v2: New
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> 
> > 
> > On Mon, Apr 10, 2017 at 11:22:33AM +0300, Kirill Tkhai wrote:
> >> v3: pr_err() -> pr_info()
> >> v2: New
> >>
> >> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> >> ---
> >>  criu/namespaces.c |   34 ++++++++++++++++++++++++++++++++++
> >>  1 file changed, 34 insertions(+)
> >>
> >> diff --git a/criu/namespaces.c b/criu/namespaces.c
> >> index 3562f9a2a..8bc876465 100644
> >> --- a/criu/namespaces.c
> >> +++ b/criu/namespaces.c
> >> @@ -14,6 +14,7 @@
> >>  #include <limits.h>
> >>  #include <errno.h>
> >>  #include <sys/ioctl.h>
> >> +#include <sys/ptrace.h>
> >>  
> >>  #include "page.h"
> >>  #include "rst-malloc.h"
> >> @@ -24,6 +25,7 @@
> >>  #include "mount.h"
> >>  #include "pstree.h"
> >>  #include "namespaces.h"
> >> +#include "restore.h"
> >>  #include "net.h"
> >>  #include "cgroup.h"
> >>  #include "kerndat.h"
> >> @@ -1508,6 +1510,33 @@ static void unsc_msg_pid_fd(struct unsc_msg *um, pid_t *pid, int *fd)
> >>  	}
> >>  }
> >>  
> >> +static void usernsd_handler(int signal, siginfo_t *siginfo, void *data)
> >> +{
> >> +	pid_t pid = siginfo->si_pid;
> >> +	int status;
> >> +	int exit;
> >> +
> >> +	if (siginfo->si_code == CLD_TRAPPED && siginfo->si_status == SIGCHLD) {
> >> +		/* The usernsd is ptraced. Allow it to handle SIGCHLD */
> >> +		ptrace(PTRACE_CONT, siginfo->si_pid, 0, SIGCHLD);
> > 
> > Who ptraces usernsd? Signals can be merged, so you have to user wait4 to
> > get all pids?

Pls, tell something about this ^^^^

> >> +		return;
> >> +	}
> >> +
> >> +	while (pid) {
> >> +		pid = waitpid(-1, &status, WNOHANG);
> >> +		if (pid <= 0)
> >> +			return;
> >> +
> >> +		exit = WIFEXITED(status);
> >> +		status = exit ? WEXITSTATUS(status) : WTERMSIG(status);
> >> +		if (status) {
> >> +			futex_abort_and_wake(&task_entries->nr_in_progress);
> >> +			pr_err("%d finished abnormal\n", pid);
> >> +		} else
> >> +			pr_info("%d exited normally\n", pid);
> >> +	}
> >> +}
> >> +
> >>  static int usernsd(int sk)
> >>  {
> >>  	struct sockaddr_un addr;
> >> @@ -1537,6 +1566,11 @@ static int usernsd(int sk)
> >>  		return -1;
> >>  	}
> >>  
> >> +	if (criu_signals_setup(usernsd_handler) < 0) {
> >> +		pr_err("Can't setup handler\n");
> >> +		return -1;
> >> +	}
> >> +
> >>  	while (1) {
> >>  		struct unsc_msg um;
> >>  		static char msg[MAX_UNSFD_MSG_SIZE];
> >>