tree-wide: port to fd_wait_for_event()

Prompted by the discussion on #16110, let's migrate more code to
fd_wait_for_event().

This only leaves 7 places where we call into poll()/poll() directly in
our entire codebase. (one of which is fd_wait_for_event() itself)

src/shared/utmp-wtmp.c

@@ -14,6 +14,7 @@
 #include "alloc-util.h"
 #include "fd-util.h"
 #include "hostname-util.h"
+#include "io-util.h"
 #include "macro.h"
 #include "memory-util.h"
 #include "path-util.h"
@@ -297,7 +298,7 @@ int utmp_put_runlevel(int runlevel, int previous) {
         return write_entry_both(&store);
 }
 
-#define TIMEOUT_MSEC 50
+#define TIMEOUT_USEC (50 * USEC_PER_MSEC)
 
 static int write_to_terminal(const char *tty, const char *message) {
         _cleanup_close_ int fd = -1;
@@ -315,14 +316,10 @@ static int write_to_terminal(const char *tty, const char *message) {
         p = message;
         left = strlen(message);
 
-        end = now(CLOCK_MONOTONIC) + TIMEOUT_MSEC*USEC_PER_MSEC;
+        end = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;
 
         while (left > 0) {
                 ssize_t n;
-                struct pollfd pollfd = {
-                        .fd = fd,
-                        .events = POLLOUT,
-                };
                 usec_t t;
                 int k;
 
@@ -331,13 +328,11 @@ static int write_to_terminal(const char *tty, const char *message) {
                 if (t >= end)
                         return -ETIME;
 
-                k = poll(&pollfd, 1, (end - t) / USEC_PER_MSEC);
+                k = fd_wait_for_event(fd, POLLOUT, end - t);
                 if (k < 0)
-                        return -errno;
+                        return k;
                 if (k == 0)
                         return -ETIME;
-                if (pollfd.revents & POLLNVAL)
-                        return -EBADF;
 
                 n = write(fd, p, left);
                 if (n < 0) {

src/shared/varlink.c

@@ -6,6 +6,7 @@
 #include "errno-util.h"
 #include "fd-util.h"
 #include "hashmap.h"
+#include "io-util.h"
 #include "list.h"
 #include "process-util.h"
 #include "set.h"
@@ -1003,8 +1004,6 @@ static void handle_revents(Varlink *v, int revents) {
 }
 
 int varlink_wait(Varlink *v, usec_t timeout) {
-        struct timespec ts;
-        struct pollfd pfd;
         int r, fd, events;
         usec_t t;
 
@@ -1038,23 +1037,13 @@ int varlink_wait(Varlink *v, usec_t timeout) {
         if (events < 0)
                 return events;
 
-        pfd = (struct pollfd) {
-                .fd = fd,
-                .events = events,
-        };
-
-        r = ppoll(&pfd, 1,
-                  t == USEC_INFINITY ? NULL : timespec_store(&ts, t),
-                  NULL);
+        r = fd_wait_for_event(fd, events, t);
         if (r < 0)
-                return -errno;
+                return r;
         if (r == 0)
                 return 0;
 
-        if (pfd.revents & POLLNVAL)
-                return -EBADF;
-
-        handle_revents(v, pfd.revents);
+        handle_revents(v, r);
         return 1;
 }
 
@@ -1123,8 +1112,6 @@ int varlink_flush(Varlink *v) {
                 return -ENOTCONN;
 
         for (;;) {
-                struct pollfd pfd;
-
                 if (v->output_buffer_size == 0)
                         break;
                 if (v->write_disconnected)
@@ -1138,20 +1125,13 @@ int varlink_flush(Varlink *v) {
                         continue;
                 }
 
-                pfd = (struct pollfd) {
-                        .fd = v->fd,
-                        .events = POLLOUT,
-                };
-
-                r = poll(&pfd, 1, -1);
+                r = fd_wait_for_event(v->fd, POLLOUT, USEC_INFINITY);
                 if (r < 0)
-                        return -errno;
+                        return r;
 
-                assert(r > 0);
-                if (pfd.revents & POLLNVAL)
-                        return -EBADF;
+                assert(r != 0);
 
-                handle_revents(v, pfd.revents);
+                handle_revents(v, r);
         }
 
         return ret;