Merge pull request #25483 from poettering/ppoll-usec-eintr

ppoll() + EINTR fixes

11 files changed, 101 insertions, 39 deletions

diff --git a/src/basic/io-util.c b/src/basic/io-util.c
index cdad939aa6..f642beca3a 100644
--- a/src/basic/io-util.c
+++ b/src/basic/io-util.c
@@ -161,6 +161,21 @@ int ppoll_usec(struct pollfd *fds, size_t nfds, usec_t timeout) {
 
         assert(fds || nfds == 0);
 
+        /* This is a wrapper around ppoll() that does primarily two things:
+         *
+         *  ✅ Takes a usec_t instead of a struct timespec
+         *
+         *  ✅ Guarantees that if an invalid fd is specified we return EBADF (i.e. converts POLLNVAL to
+         *     EBADF). This is done because EBADF is a programming error usually, and hence should bubble up
+         *     as error, and not be eaten up as non-error POLLNVAL event.
+         *
+         *  ⚠️ ⚠️ ⚠️ Note that this function does not add any special handling for EINTR. Don't forget
+         *  poll()/ppoll() will return with EINTR on any received signal always, there is no automatic
+         *  restarting via SA_RESTART available. Thus, typically you want to handle EINTR not as an error,
+         *  but just as reason to restart things, under the assumption you use a more appropriate mechanism
+         *  to handle signals, such as signalfd() or signal handlers. ⚠️ ⚠️ ⚠️
+         */
+
         if (nfds == 0)
                 return 0;
 
@@ -188,6 +203,9 @@ int fd_wait_for_event(int fd, int event, usec_t timeout) {
         };
         int r;
 
+        /* ⚠️ ⚠️ ⚠️ Keep in mind you almost certainly want to handle -EINTR gracefully in the caller, see
+         * ppoll_usec() above! ⚠️ ⚠️ ⚠️ */
+
         r = ppoll_usec(&pollfd, 1, timeout);
         if (r <= 0)
                 return r;
diff --git a/src/home/homework-luks.c b/src/home/homework-luks.c
index 97fb5a1051..5e1d5bbd65 100644
--- a/src/home/homework-luks.c
+++ b/src/home/homework-luks.c
@@ -2017,9 +2017,12 @@ static int wait_for_devlink(const char *path) {
                 if (w >= until)
                         return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Device link %s still hasn't shown up, giving up.", path);
 
-                r = fd_wait_for_event(inotify_fd, POLLIN, usec_sub_unsigned(until, w));
-                if (r < 0)
+                r = fd_wait_for_event(inotify_fd, POLLIN, until - w);
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         return log_error_errno(r, "Failed to watch inotify: %m");
+                }
 
                 (void) flush_fd(inotify_fd);
         }
diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c
index c94befef73..253f41c636 100644
--- a/src/libsystemd/sd-bus/bus-socket.c
+++ b/src/libsystemd/sd-bus/bus-socket.c
@@ -1308,8 +1308,11 @@ int bus_socket_process_opening(sd_bus *b) {
         assert(b->state == BUS_OPENING);
 
         events = fd_wait_for_event(b->output_fd, POLLOUT, 0);
-        if (events < 0)
+        if (events < 0) {
+                if (ERRNO_IS_TRANSIENT(events))
+                        return 0;
                 return events;
+        }
         if (!(events & (POLLOUT|POLLERR|POLLHUP)))
                 return 0;
 
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index ba5ef7de00..c75276f4ba 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -2465,8 +2465,11 @@ _public_ int sd_bus_call(
                         left = UINT64_MAX;
 
                 r = bus_poll(bus, true, left);
-                if (r < 0)
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         goto fail;
+                }
                 if (r == 0) {
                         r = -ETIMEDOUT;
                         goto fail;
@@ -3321,6 +3324,7 @@ static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec) {
 }
 
 _public_ int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec) {
+        int r;
 
         assert_return(bus, -EINVAL);
         assert_return(bus = bus_resolve(bus), -ENOPKG);
@@ -3335,7 +3339,11 @@ _public_ int sd_bus_wait(sd_bus *bus, uint64_t timeout_usec) {
         if (bus->rqueue_size > 0)
                 return 0;
 
-        return bus_poll(bus, false, timeout_usec);
+        r = bus_poll(bus, false, timeout_usec);
+        if (r < 0 && ERRNO_IS_TRANSIENT(r))
+                return 1; /* treat EINTR as success, but let's exit, so that the caller will call back into us soon. */
+
+        return r;
 }
 
 _public_ int sd_bus_flush(sd_bus *bus) {
@@ -3377,8 +3385,12 @@ _public_ int sd_bus_flush(sd_bus *bus) {
                         return 0;
 
                 r = bus_poll(bus, false, UINT64_MAX);
-                if (r < 0)
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
+
                         return r;
+                }
         }
 }
 
diff --git a/src/libsystemd/sd-netlink/sd-netlink.c b/src/libsystemd/sd-netlink/sd-netlink.c
index feb751a848..b99abae640 100644
--- a/src/libsystemd/sd-netlink/sd-netlink.c
+++ b/src/libsystemd/sd-netlink/sd-netlink.c
@@ -464,13 +464,18 @@ static int netlink_poll(sd_netlink *nl, bool need_more, usec_t timeout_usec) {
 }
 
 int sd_netlink_wait(sd_netlink *nl, uint64_t timeout_usec) {
+        int r;
+
         assert_return(nl, -EINVAL);
         assert_return(!netlink_pid_changed(nl), -ECHILD);
 
         if (nl->rqueue_size > 0)
                 return 0;
 
-        return netlink_poll(nl, false, timeout_usec);
+        r = netlink_poll(nl, false, timeout_usec);
+        if (r < 0 && ERRNO_IS_TRANSIENT(r)) /* Convert EINTR to "something happened" and give user a chance to run some code before calling back into us */
+                return 1;
+        return r;
 }
 
 static int timeout_compare(const void *a, const void *b) {
diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index f62efa87aa..1c9048670b 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -868,11 +868,14 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) {
 }
 
 static int sendmsg_loop(int fd, struct msghdr *mh, int flags) {
+        usec_t end;
         int r;
 
         assert(fd >= 0);
         assert(mh);
 
+        end = usec_add(now(CLOCK_MONOTONIC), SEND_TIMEOUT_USEC);
+
         for (;;) {
                 if (sendmsg(fd, mh, flags) >= 0)
                         return 0;
@@ -881,20 +884,26 @@ static int sendmsg_loop(int fd, struct msghdr *mh, int flags) {
                 if (errno != EAGAIN)
                         return -errno;
 
-                r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC);
-                if (r < 0)
+                r = fd_wait_for_event(fd, POLLOUT, LESS_BY(end, now(CLOCK_MONOTONIC)));
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         return r;
+                }
                 if (r == 0)
                         return -ETIMEDOUT;
         }
 }
 
 static int write_loop(int fd, void *message, size_t length) {
+        usec_t end;
         int r;
 
         assert(fd >= 0);
         assert(message);
 
+        end = usec_add(now(CLOCK_MONOTONIC), SEND_TIMEOUT_USEC);
+
         for (;;) {
                 if (write(fd, message, length) >= 0)
                         return 0;
@@ -903,9 +912,12 @@ static int write_loop(int fd, void *message, size_t length) {
                 if (errno != EAGAIN)
                         return -errno;
 
-                r = fd_wait_for_event(fd, POLLOUT, SEND_TIMEOUT_USEC);
-                if (r < 0)
+                r = fd_wait_for_event(fd, POLLOUT, LESS_BY(end, now(CLOCK_MONOTONIC)));
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
                         return r;
+                }
                 if (r == 0)
                         return -ETIMEDOUT;
         }
diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index e7db23c201..1ad5ddd503 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -235,8 +235,7 @@ int ask_password_plymouth(
                 if (notify < 0)
                         return -errno;
 
-                r = inotify_add_watch(notify, flag_file, IN_ATTRIB); /* for the link count */
-                if (r < 0)
+                if (inotify_add_watch(notify, flag_file, IN_ATTRIB) < 0) /* for the link count */
                         return -errno;
         }
 
@@ -244,8 +243,7 @@ int ask_password_plymouth(
         if (fd < 0)
                 return -errno;
 
-        r = connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
-        if (r < 0)
+        if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
                 return -errno;
 
         if (FLAGS_SET(flags, ASK_PASSWORD_ACCEPT_CACHED)) {
@@ -469,10 +467,9 @@ int ask_password_tty(
                 new_termios.c_cc[VMIN] = 1;
                 new_termios.c_cc[VTIME] = 0;
 
-                if (tcsetattr(ttyfd, TCSADRAIN, &new_termios) < 0) {
-                        r = -errno;
+                r = RET_NERRNO(tcsetattr(ttyfd, TCSADRAIN, &new_termios));
+                if (r < 0)
                         goto finish;
-                }
 
                 reset_tty = true;
         }
@@ -496,11 +493,11 @@ int ask_password_tty(
                 else
                         timeout = USEC_INFINITY;
 
-                if (flag_file)
-                        if (access(flag_file, F_OK) < 0) {
-                                r = -errno;
+                if (flag_file) {
+                        r = RET_NERRNO(access(flag_file, F_OK));
+                        if (r < 0)
                                 goto finish;
-                        }
+                }
 
                 r = ppoll_usec(pollfd, notify >= 0 ? 2 : 1, timeout);
                 if (r == -EINTR)
@@ -752,10 +749,10 @@ int ask_password_agent(
                         r = -errno;
                         goto finish;
                 }
-                if (inotify_add_watch(notify, "/run/systemd/ask-password", IN_ATTRIB /* for mtime */) < 0) {
-                        r = -errno;
+
+                r = RET_NERRNO(inotify_add_watch(notify, "/run/systemd/ask-password", IN_ATTRIB /* for mtime */));
+                if (r < 0)
                         goto finish;
-                }
         }
 
         fd = mkostemp_safe(temp);
@@ -818,10 +815,9 @@ int ask_password_agent(
         final[sizeof(final)-10] = 's';
         final[sizeof(final)-9] = 'k';
 
-        if (rename(temp, final) < 0) {
-                r = -errno;
+        r = RET_NERRNO(rename(temp, final));
+        if (r < 0)
                 goto finish;
-        }
 
         zero(pollfd);
         pollfd[FD_SOCKET].fd = socket_fd;
diff --git a/src/shared/barrier.c b/src/shared/barrier.c
index cbe54a60cd..d76a61a5db 100644
--- a/src/shared/barrier.c
+++ b/src/shared/barrier.c
@@ -92,7 +92,6 @@
  */
 int barrier_create(Barrier *b) {
         _unused_ _cleanup_(barrier_destroyp) Barrier *staging = b;
-        int r;
 
         assert(b);
 
@@ -104,8 +103,7 @@ int barrier_create(Barrier *b) {
         if (b->them < 0)
                 return -errno;
 
-        r = pipe2(b->pipe, O_CLOEXEC | O_NONBLOCK);
-        if (r < 0)
+        if (pipe2(b->pipe, O_CLOEXEC | O_NONBLOCK) < 0)
                 return -errno;
 
         staging = NULL;
diff --git a/src/shared/utmp-wtmp.c b/src/shared/utmp-wtmp.c
index d2c8473c60..37a5bf7990 100644
--- a/src/shared/utmp-wtmp.c
+++ b/src/shared/utmp-wtmp.c
@@ -12,6 +12,7 @@
 #include <utmpx.h>
 
 #include "alloc-util.h"
+#include "errno-util.h"
 #include "fd-util.h"
 #include "hostname-util.h"
 #include "io-util.h"
@@ -292,13 +293,15 @@ static int write_to_terminal(const char *tty, const char *message) {
         assert(message);
 
         fd = open(tty, O_WRONLY|O_NONBLOCK|O_NOCTTY|O_CLOEXEC);
-        if (fd < 0 || !isatty(fd))
+        if (fd < 0)
                 return -errno;
+        if (!isatty(fd))
+                return -ENOTTY;
 
         p = message;
         left = strlen(message);
 
-        end = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;
+        end = usec_add(now(CLOCK_MONOTONIC), TIMEOUT_USEC);
 
         while (left > 0) {
                 ssize_t n;
@@ -306,19 +309,21 @@ static int write_to_terminal(const char *tty, const char *message) {
                 int k;
 
                 t = now(CLOCK_MONOTONIC);
-
                 if (t >= end)
                         return -ETIME;
 
                 k = fd_wait_for_event(fd, POLLOUT, end - t);
-                if (k < 0)
+                if (k < 0) {
+                        if (ERRNO_IS_TRANSIENT(k))
+                                continue;
                         return k;
+                }
                 if (k == 0)
                         return -ETIME;
 
                 n = write(fd, p, left);
                 if (n < 0) {
-                        if (errno == EAGAIN)
+                        if (ERRNO_IS_TRANSIENT(errno))
                                 continue;
 
                         return -errno;
diff --git a/src/shared/varlink.c b/src/shared/varlink.c
index 4f7ac97689..4d2cfee491 100644
--- a/src/shared/varlink.c
+++ b/src/shared/varlink.c
@@ -1025,7 +1025,7 @@ static void handle_revents(Varlink *v, int revents) {
                 if ((revents & (POLLOUT|POLLHUP)) == 0)
                         return;
 
-                varlink_log(v, "Anynchronous connection completed.");
+                varlink_log(v, "Asynchronous connection completed.");
                 v->connecting = false;
         } else {
                 /* Note that we don't care much about POLLIN/POLLOUT here, we'll just try reading and writing
@@ -1075,6 +1075,9 @@ int varlink_wait(Varlink *v, usec_t timeout) {
                 return events;
 
         r = fd_wait_for_event(fd, events, t);
+        if (r < 0 && ERRNO_IS_TRANSIENT(r)) /* Treat EINTR as not a timeout, but also nothing happened, and
+                                             * the caller gets a chance to call back into us */
+                return 1;
         if (r <= 0)
                 return r;
 
@@ -1161,8 +1164,12 @@ int varlink_flush(Varlink *v) {
                 }
 
                 r = fd_wait_for_event(v->fd, POLLOUT, USEC_INFINITY);
-                if (r < 0)
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r))
+                                continue;
+
                         return varlink_log_errno(v, r, "Poll failed on fd: %m");
+                }
 
                 assert(r != 0);
 
diff --git a/src/stdio-bridge/stdio-bridge.c b/src/stdio-bridge/stdio-bridge.c
index 3c5ba074c7..6e8f2bbe3c 100644
--- a/src/stdio-bridge/stdio-bridge.c
+++ b/src/stdio-bridge/stdio-bridge.c
@@ -242,8 +242,11 @@ static int run(int argc, char *argv[]) {
                 };
 
                 r = ppoll_usec(p, ELEMENTSOF(p), t);
-                if (r < 0)
+                if (r < 0) {
+                        if (ERRNO_IS_TRANSIENT(r)) /* don't be bothered by signals, i.e. EINTR */
+                                continue;
                         return log_error_errno(r, "ppoll() failed: %m");
+                }
         }
 
         return 0;