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osmo-uecups
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dameon: Handle multiple coalesced SIGCHLD 

It turns out signalfd is much less useful than one would assume:
https://ldpreload.com/blog/signalfd-is-useless

Change-Id: I16bc5b7de72843c2ae18b982bfd967a7105313e4
This commit is contained in:
Harald Welte 2020-04-21 22:46:34 +02:00
parent 8e2ad14487
commit f9bb1777c7
1 changed files with 29 additions and 10 deletions
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39
daemon/main.c
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@ -7,6 +7,7 @@
#include <stdio.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/signalfd.h>
#include <signal.h>
#include <errno.h>
@ -334,26 +335,22 @@ static struct subprocess *subprocess_by_pid(struct gtp_daemon *d, pid_t pid)
return NULL;
}
static void sigchild_cb(struct osmo_signalfd *osfd, const struct signalfd_siginfo *fdsi)
static void child_terminated(struct gtp_daemon *d, int pid, int status)
{
struct gtp_daemon *d = osfd->data;
struct subprocess *sproc;
json_t *jterm_ind;
OSMO_ASSERT(fdsi->ssi_signo == SIGCHLD);
LOGP(DUECUPS, LOGL_DEBUG, "SIGCHLD receive from pid %u; status=%d\n", pid, status);
LOGP(DUECUPS, LOGL_DEBUG, "SIGCHLD receive from pid %u; status=%d\n",
fdsi->ssi_pid, fdsi->ssi_status);
sproc = subprocess_by_pid(d, fdsi->ssi_pid);
sproc = subprocess_by_pid(d, pid);
if (!sproc) {
LOGP(DUECUPS, LOGL_NOTICE, "subprocess %u terminated (status=%d) but we don't know it?\n",
fdsi->ssi_pid, fdsi->ssi_status);
pid, status);
return;
}
/* FIXME: generate prog_term_ind towards control plane */
jterm_ind = gen_uecups_term_ind(fdsi->ssi_pid, fdsi->ssi_status);
/* generate prog_term_ind towards control plane */
jterm_ind = gen_uecups_term_ind(pid, status);
if (!jterm_ind)
return;
@ -363,6 +360,28 @@ static void sigchild_cb(struct osmo_signalfd *osfd, const struct signalfd_siginf
talloc_free(sproc);
}
static void sigchild_cb(struct osmo_signalfd *osfd, const struct signalfd_siginfo *fdsi)
{
struct gtp_daemon *d = osfd->data;
int pid, status;
OSMO_ASSERT(fdsi->ssi_signo == SIGCHLD);
child_terminated(d, fdsi->ssi_pid, fdsi->ssi_status);
/* it is known that classic signals coalesce: If you get multiple signals of the
* same type before a process is scheduled, the subsequent signaals are dropped. This
* makes sense for SIGINT or something like this, but for SIGCHLD carrying the PID of
* the terminated process, it doesn't really. Linux had the chance to fix this when
* introducing signalfd() - but the developers decided not to fix it. So the signalfd_siginfo
* contains the PID of one process that terminated - but there may be any number of other
* processes that also have terminated, and for which we don't get events this way. */
while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
child_terminated(d, pid, status);
}
static json_t *gen_uecups_start_res(pid_t pid, const char *result)
{
json_t *ret = gen_uecups_result("start_program_res", result);