Messages in this thread | | | Subject | Re: [PATCH] signalfd: fill in ssi_int for posix timers and message queues | From | Nathan Lynch <> | Date | Mon, 05 Jul 2010 07:22:55 -0500 |
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Hello Davide,
On Sat, 2010-07-03 at 12:09 -0700, Davide Libenzi wrote: > On Fri, 2 Jul 2010, Nathan Lynch wrote: > > > If signalfd is used to consume a signal generated by a POSIX interval > > timer or POSIX message queue, the ssi_int field does not reflect the > > data (sigevent->sigev_value) supplied to timer_create(2) or > > mq_notify(3). (The ssi_ptr field, however, is filled in.) > > > > This behavior differs from signalfd's treatment of sigqueue-generated > > signals -- see the default case in signalfd_copyinfo. It also gives > > results that differ from the case when a signal is handled > > conventionally via a sigaction-registered handler. > > > > So, set signalfd_siginfo->ssi_int in the remaining cases (__SI_TIMER, > > __SI_MESGQ) where ssi_ptr is set. > > > > Signed-off-by: Nathan Lynch <ntl@pobox.com> > > --- > > fs/signalfd.c | 2 ++ > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > diff --git a/fs/signalfd.c b/fs/signalfd.c > > index f329849..1c5a6ad 100644 > > --- a/fs/signalfd.c > > +++ b/fs/signalfd.c > > @@ -88,6 +88,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, > > err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); > > err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); > > err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); > > + err |= __put_user(kinfo->si_int, &uinfo->ssi_int); > > break; > > case __SI_POLL: > > err |= __put_user(kinfo->si_band, &uinfo->ssi_band); > > @@ -111,6 +112,7 @@ static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, > > err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); > > err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); > > err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); > > + err |= __put_user(kinfo->si_int, &uinfo->ssi_int); > > break; > > default: > > I am fine with it, but I now noticed that signalfd_copyinfo() got out of > sync from copy_siginfo_to_user(), which should match. > Do you mind aligning that too, as part of your patch? > An adding a comment on the lines of the one in copy_siginfo_to_user() to > signalfd_copyinfo() too?
Sorry, I'm not sure I understand. Are you saying that copy_siginfo_to_user should have analogous lines added to assign to si_int? That's actually not necessary if I read the code correctly: in struct siginfo, si_ptr and si_int are members of a sigval union, so assigning to the former covers the latter. signalfd must assign both ssi_ptr and ssi_int since they occupy different locations in signalfd_siginfo.
Perhaps the attached testcases make the problem (as I see it) more clear? The final assertion fails without this patch.
#include <sys/signalfd.h> #include <assert.h> #include <errno.h> #include <mqueue.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h>
static int handler_run; static const union sigval my_sigval = { .sival_int = 42, };
static const char msgbuf[] = "hello";
#define bail(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0);
static void handler(int sig, siginfo_t *si, void *notused) { assert(si->si_code == SI_MESGQ); assert(si->si_ptr == my_sigval.sival_ptr); /* Succeeds */ assert(si->si_int == my_sigval.sival_int); /* Succeeds */
/* This should run only once */ assert(handler_run == 0); handler_run++; }
int main(int argc, char *argv[]) { struct signalfd_siginfo fdsi; struct sigaction newact; struct sigevent sev; struct mq_attr attr; sigset_t mask; size_t msglen; char *rcvbuf; mqd_t mqdes; ssize_t s; int sfd;
if (argc != 2) { fprintf(stderr, "Usage: %s <mq-name>\n", argv[0]); exit(EXIT_FAILURE); }
newact.sa_flags = SA_SIGINFO | SA_RESETHAND; newact.sa_sigaction = handler; sigemptyset(&newact.sa_mask);
if (sigaction(SIGRTMIN, &newact, NULL) == -1) bail("sigaction");
mqdes = mq_unlink(argv[1]); if (mqdes == -1 && errno != ENOENT) bail("mq_unlink");
mqdes = mq_open(argv[1], (O_RDWR | O_CREAT), 0600, NULL); if (mqdes == (mqd_t) -1) bail("mq_open");
memset(&sev, 0, sizeof(sev)); sev.sigev_notify = SIGEV_SIGNAL; sev.sigev_signo = SIGRTMIN; sev.sigev_value = my_sigval;
if (mq_notify(mqdes, &sev) == -1) bail("mq_notify");
if (mq_send(mqdes, msgbuf, sizeof(msgbuf), 0) == -1) bail("mq_send");
while (!handler_run) usleep(100000);
if (mq_getattr(mqdes, &attr) == -1) bail("mq_getattr");
msglen = attr.mq_msgsize;
rcvbuf = malloc(msglen); if (!rcvbuf) bail("malloc");
/* Empty the queue */ if (mq_receive(mqdes, rcvbuf, msglen, NULL) != sizeof(msgbuf)) bail("mq_receive");
/* Inhibit default SIGRTMIN handling */ sigemptyset(&mask); sigaddset(&mask, SIGRTMIN); if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) bail("sigprocmask");
/* Reregister the notifier and post another message */ if (mq_notify(mqdes, &sev) == -1) bail("mq_notify");
if (mq_send(mqdes, msgbuf, sizeof(msgbuf), 0) == -1) bail("mq_send");
sfd = signalfd(-1, &mask, 0); if (sfd == -1) bail("signalfd");
/* Handle the signal */ s = read(sfd, &fdsi, sizeof(struct signalfd_siginfo)); if (s != sizeof(struct signalfd_siginfo)) bail("read");
assert(fdsi.ssi_code == SI_MESGQ); assert(fdsi.ssi_ptr == (unsigned long)my_sigval.sival_ptr); /* Succeeds */ assert(fdsi.ssi_int == my_sigval.sival_int); /* Fails */
exit(EXIT_SUCCESS); } #include <sys/signalfd.h> #include <assert.h> #include <stdlib.h> #include <unistd.h> #include <stdio.h> #include <signal.h> #include <string.h> #include <time.h>
static int handler_run; static const union sigval my_sigval = { .sival_int = 42, };
#define bail(msg) \ do { perror(msg); exit(EXIT_FAILURE); } while (0);
static void handler(int sig, siginfo_t *si, void *notused) { assert(si->si_code == SI_TIMER); assert(si->si_ptr == my_sigval.sival_ptr); /* Succeeds */ assert(si->si_int == my_sigval.sival_int); /* Succeeds */
/* This should run only once */ assert(handler_run == 0); handler_run++; }
int main(void) { struct signalfd_siginfo fdsi; struct sigaction newact; struct itimerspec its; struct sigevent sev; timer_t timerid; sigset_t mask; ssize_t s; int sfd;
newact.sa_flags = SA_SIGINFO | SA_RESETHAND; newact.sa_sigaction = handler; sigemptyset(&newact.sa_mask);
if (sigaction(SIGRTMIN, &newact, NULL) == -1) bail("sigaction");
memset(&sev, 0, sizeof(sev)); sev.sigev_notify = SIGEV_SIGNAL; sev.sigev_signo = SIGRTMIN; sev.sigev_value = my_sigval;
if (timer_create(CLOCK_REALTIME, &sev, &timerid) == -1) bail("timer_create");
/* Timer expires just once */ its.it_value.tv_sec = 0; its.it_value.tv_nsec = 100; its.it_interval.tv_sec = 0; its.it_interval.tv_nsec = 0;
/* Arm timer */ if (timer_settime(timerid, 0, &its, NULL) == -1) bail("timer_settime");
/* Wait for timer to expire, which executes the handler */ while (!handler_run) usleep(100000);
/* Inhibit default SIGRTMIN handling */ sigemptyset(&mask); sigaddset(&mask, SIGRTMIN); if (sigprocmask(SIG_BLOCK, &mask, NULL) == -1) bail("sigprocmask");
sfd = signalfd(-1, &mask, 0); if (sfd == -1) bail("signalfd");
/* Re-arm timer */ if (timer_settime(timerid, 0, &its, NULL) == -1) bail("timer_settime");
/* Block until timer expiration */ s = read(sfd, &fdsi, sizeof(struct signalfd_siginfo)); if (s != sizeof(struct signalfd_siginfo)) bail("read");
assert(fdsi.ssi_code == SI_TIMER); assert(fdsi.ssi_ptr == (unsigned long)my_sigval.sival_ptr); /* Succeeds */ assert(fdsi.ssi_int == my_sigval.sival_int); /* Fails */
return EXIT_SUCCESS; }
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