Cleanup: autoconf 'dirfd' detection

[lttng-tools.git] / src / common / compat / compat-epoll.c

diff --git a/src/common/compat/compat-epoll.c b/src/common/compat/compat-epoll.c
index 58f50cc94dd83e33448ca31ebdb2fd2594fee88a..9055f51291475ae31b9508f7197d3eb581d2cc89 100644 (file)
--- a/src/common/compat/compat-epoll.c
+++ b/src/common/compat/compat-epoll.c
@@ -1,18 +1,8 @@
 /*
- * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License, version 2 only,
- * as published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _LGPL_SOURCE
@@ -23,6 +13,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <stdbool.h>
 
 #include <common/error.h>
 #include <common/defaults.h>
@@ -31,7 +22,17 @@
 
 #include "poll.h"
 
-unsigned int poll_max_size;
+/*
+ * Maximum number of fd we can monitor.
+ *
+ * For epoll(7), /proc/sys/fs/epoll/max_user_watches (since Linux 2.6.28) will
+ * be used for the maximum size of the poll set. If this interface is not
+ * available, according to the manpage, the max_user_watches value is 1/25 (4%)
+ * of the available low memory divided by the registration cost in bytes which
+ * is 90 bytes on a 32-bit kernel and 160 bytes on a 64-bit kernel.
+ *
+ */
+static unsigned int poll_max_size;
 
 /*
  * Resize the epoll events structure of the new size.
@@ -67,6 +68,7 @@ error:
 /*
  * Create epoll set and allocate returned events structure.
  */
+LTTNG_HIDDEN
 int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
 {
        int ret;
@@ -76,8 +78,9 @@ int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
        }
 
        if (!poll_max_size) {
-               ERR("poll_max_size not initialized yet");
-               goto error;
+               if (lttng_poll_set_max_size()) {
+                       goto error;
+               }
        }
 
        /* Don't bust the limit here */
@@ -118,6 +121,7 @@ error:
 /*
  * Add a fd to the epoll set with requesting events.
  */
+LTTNG_HIDDEN
 int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
 {
        int ret;
@@ -165,6 +169,7 @@ error:
 /*
  * Remove a fd from the epoll set.
  */
+LTTNG_HIDDEN
 int compat_epoll_del(struct lttng_poll_event *events, int fd)
 {
        int ret;
@@ -196,10 +201,54 @@ error:
        return -1;
 }
 
+/*
+ * Set an fd's events.
+ */
+LTTNG_HIDDEN
+int compat_epoll_mod(struct lttng_poll_event *events, int fd, uint32_t req_events)
+{
+       int ret;
+       struct epoll_event ev;
+
+       if (events == NULL || fd < 0 || events->nb_fd == 0) {
+               goto error;
+       }
+
+       /*
+        * Zero struct epoll_event to ensure all representations of its
+        * union are zeroed.
+        */
+       memset(&ev, 0, sizeof(ev));
+       ev.events = req_events;
+       ev.data.fd = fd;
+
+       ret = epoll_ctl(events->epfd, EPOLL_CTL_MOD, fd, &ev);
+       if (ret < 0) {
+               switch (errno) {
+               case ENOENT:
+               case EPERM:
+                       /* Print PERROR and goto end not failing. Show must go on. */
+                       PERROR("epoll_ctl MOD");
+                       goto end;
+               default:
+                       PERROR("epoll_ctl MOD fatal");
+                       goto error;
+               }
+       }
+
+end:
+       return 0;
+
+error:
+       return -1;
+}
+
 /*
  * Wait on epoll set. This is a blocking call of timeout value.
  */
-int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
+LTTNG_HIDDEN
+int compat_epoll_wait(struct lttng_poll_event *events, int timeout,
+               bool interruptible)
 {
        int ret;
        uint32_t new_size;
@@ -208,7 +257,6 @@ int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
                ERR("Wrong arguments in compat_epoll_wait");
                goto error;
        }
-       assert(events->nb_fd >= 0);
 
        if (events->nb_fd == 0) {
                errno = EINVAL;
@@ -232,10 +280,11 @@ int compat_epoll_wait(struct lttng_poll_event *events, int timeout)
 
        do {
                ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
-       } while (ret == -1 && errno == EINTR);
+       } while (!interruptible && ret == -1 && errno == EINTR);
        if (ret < 0) {
-               /* At this point, every error is fatal */
-               PERROR("epoll_wait");
+               if (errno != EINTR) {
+                       PERROR("epoll_wait");
+               }
                goto error;
        }
 
@@ -252,6 +301,7 @@ error:
 /*
  * Setup poll set maximum size.
  */
+LTTNG_HIDDEN
 int compat_epoll_set_max_size(void)
 {
        int ret, fd, retval = 0;
@@ -260,7 +310,15 @@ int compat_epoll_set_max_size(void)
 
        fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
        if (fd < 0) {
-               retval = -1;
+               /*
+                * Failing on opening [1] is not an error per see. [1] was
+                * introduced in Linux 2.6.28 but epoll is available since
+                * 2.5.44. Hence, goto end and set a default value without
+                * setting an error return value.
+                *
+                * [1] /proc/sys/fs/epoll/max_user_watches
+                */
+               retval = 0;
                goto end;
        }