diff options
| -rw-r--r-- | util-linux/mdev.c | 26 |
1 files changed, 17 insertions, 9 deletions
diff --git a/util-linux/mdev.c b/util-linux/mdev.c index 59dbcf0cd..8b06d3456 100644 --- a/util-linux/mdev.c +++ b/util-linux/mdev.c @@ -269,10 +269,6 @@ # define dbg3s(msg) ((void)0) #endif - -#ifndef SO_RCVBUFFORCE -#define SO_RCVBUFFORCE 33 -#endif static const char keywords[] ALIGN1 = "add\0remove\0"; // "change\0" enum { OP_add, OP_remove }; @@ -1152,15 +1148,27 @@ static void initial_scan(char *temp) #if ENABLE_FEATURE_MDEV_DAEMON -/* uevent applet uses 16k buffer, and mmaps it before every read */ -# define BUFFER_SIZE (2 * 1024) -# define RCVBUF (2 * 1024 * 1024) +/* + * The kernel (as of v5.4) will pass up to 32 environment variables with a + * total of 2kiB on each event. On top of that the action string and device + * path are added. Using a 3kiB buffer for the event should suffice in any + * case. + * + * As far as the socket receive buffer size is concerned 2MiB proved to be too + * small (see [1]). Udevd seems to use a whooping 128MiB. The socket receive + * buffer size is just a resource limit. The buffers are allocated lazily so + * the memory is not wasted. + * + * [1] http://lists.busybox.net/pipermail/busybox/2019-December/087665.html + */ +# define USER_RCVBUF (3 * 1024) +# define KERN_RCVBUF (128 * 1024 * 1024) # define MAX_ENV 32 static void daemon_loop(char *temp, int fd) { for (;;) { - char netbuf[BUFFER_SIZE]; + char netbuf[USER_RCVBUF]; char *env[MAX_ENV]; char *s, *end; ssize_t len; @@ -1237,7 +1245,7 @@ int mdev_main(int argc UNUSED_PARAM, char **argv) * mdev -d * find /sys -name uevent -exec sh -c 'echo add >"{}"' ';' */ - fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, RCVBUF); + fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, KERN_RCVBUF); /* * Make inital scan after the uevent socket is alive and |