---
 .gitignore                 |   1 +
 Makefile                   |   6 ++
 config.mak.uname           |   1 +
 git-compat-util.h          |   8 +++
 read-cache--daemon.c (new) | 167 +++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 183 insertions(+)
 create mode 100644 read-cache--daemon.c

diff --git a/.gitignore b/.gitignore
index 70992a4..07e0cb6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -110,6 +110,7 @@
 /git-pull
 /git-push
 /git-quiltimport
+/git-read-cache--daemon
 /git-read-tree
 /git-rebase
 /git-rebase--am
diff --git a/Makefile b/Makefile
index 028749b..98d22de 100644
--- a/Makefile
+++ b/Makefile
@@ -1502,6 +1502,12 @@ ifdef HAVE_DEV_TTY
        BASIC_CFLAGS += -DHAVE_DEV_TTY
 endif
 
+ifdef HAVE_SHM
+       BASIC_CFLAGS += -DHAVE_SHM
+       EXTLIBS += -lrt
+       PROGRAM_OBJS += read-cache--daemon.o
+endif
+
 ifdef DIR_HAS_BSD_GROUP_SEMANTICS
        COMPAT_CFLAGS += -DDIR_HAS_BSD_GROUP_SEMANTICS
 endif
diff --git a/config.mak.uname b/config.mak.uname
index 23a8803..b6a37e5 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -33,6 +33,7 @@ ifeq ($(uname_S),Linux)
        HAVE_PATHS_H = YesPlease
        LIBC_CONTAINS_LIBINTL = YesPlease
        HAVE_DEV_TTY = YesPlease
+       HAVE_SHM = YesPlease
 endif
 ifeq ($(uname_S),GNU/kFreeBSD)
        NO_STRLCPY = YesPlease
diff --git a/git-compat-util.h b/git-compat-util.h
index f6d3a46..b2116ab 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -723,4 +723,12 @@ struct tm *git_gmtime_r(const time_t *, struct tm *);
 #define gmtime_r git_gmtime_r
 #endif
 
+#ifndef HAVE_SHM
+static inline int shm_open(const char *path, int flags, int mode)
+{
+       errno = ENOSYS;
+       return -1;
+}
+#endif
+
 #endif
diff --git a/read-cache--daemon.c b/read-cache--daemon.c
new file mode 100644
index 0000000..52b4067
--- /dev/null
+++ b/read-cache--daemon.c
@@ -0,0 +1,167 @@
+#include "cache.h"
+#include "sigchain.h"
+#include "unix-socket.h"
+#include "split-index.h"
+#include "pkt-line.h"
+
+static char *socket_path;
+static struct strbuf shm_index = STRBUF_INIT;
+static struct strbuf shm_sharedindex = STRBUF_INIT;
+
+static void cleanup_socket(void)
+{
+       if (socket_path)
+               unlink(socket_path);
+       if (shm_index.len)
+               shm_unlink(shm_index.buf);
+       if (shm_sharedindex.len)
+               shm_unlink(shm_sharedindex.buf);
+}
+
+static void cleanup_socket_on_signal(int sig)
+{
+       cleanup_socket();
+       sigchain_pop(sig);
+       raise(sig);
+}
+
+static void share_index(struct index_state *istate, struct strbuf *shm_path)
+{
+       struct strbuf sb = STRBUF_INIT;
+       void *map;
+       int fd;
+
+       strbuf_addf(&sb, "/git-index-%s", sha1_to_hex(istate->sha1));
+       if (shm_path->len && strcmp(sb.buf, shm_path->buf)) {
+               shm_unlink(shm_path->buf);
+               strbuf_reset(shm_path);
+       }
+       fd = shm_open(sb.buf, O_RDWR | O_CREAT | O_TRUNC, 0700);
+       if (fd < 0)
+               return;
+       /*
+        * We "lock" the shm in preparation by set its size larger
+        * than expected. The reader is supposed to check the size and
+        * ignore if shm size is different than the actual file size
+        */
+       if (ftruncate(fd, istate->mmap_size + 1)) {
+               close(fd);
+               shm_unlink(shm_path->buf);
+               return;
+       }
+       strbuf_addbuf(shm_path, &sb);
+       map = xmmap(NULL, istate->mmap_size, PROT_READ | PROT_WRITE,
+                   MAP_SHARED, fd, 0);
+       if (map == MAP_FAILED) {
+               close(fd);
+               shm_unlink(shm_path->buf);
+               return;
+       }
+       memcpy(map, istate->mmap, istate->mmap_size);
+       munmap(map, istate->mmap_size);
+       /* Now "unlock" it */
+       if (ftruncate(fd, istate->mmap_size)) {
+               close(fd);
+               shm_unlink(shm_path->buf);
+               return;
+       }
+       close(fd);
+}
+
+static void refresh()
+{
+       the_index.keep_mmap = 1;
+       if (read_cache() < 0)
+               die("could not read index");
+       share_index(&the_index, &shm_index);
+       if (the_index.split_index &&
+           the_index.split_index->base)
+               share_index(the_index.split_index->base, &shm_sharedindex);
+       discard_index(&the_index);
+}
+
+static unsigned long next;
+static int serve_cache_loop(int fd)
+{
+       struct pollfd pfd;
+       unsigned long now = time(NULL);
+
+       if (now > next)
+               return 0;
+
+       pfd.fd = fd;
+       pfd.events = POLLIN;
+       if (poll(&pfd, 1, 1000 * (next - now)) < 0) {
+               if (errno != EINTR)
+                       die_errno("poll failed");
+               return 1;
+       }
+
+       if (pfd.revents & POLLIN) {
+               int client = accept(fd, NULL, NULL);
+               if (client < 0) {
+                       warning("accept failed: %s", strerror(errno));
+                       return 1;
+               }
+               refresh();
+               close(client);
+               next = now + 600;
+       }
+       return 1;
+}
+
+static void serve_cache(const char *socket_path)
+{
+       int fd;
+
+       fd = unix_stream_listen(socket_path);
+       if (fd < 0)
+               die_errno("unable to bind to '%s'", socket_path);
+
+       refresh();
+
+       printf("ok\n");
+       fclose(stdout);
+
+       next = time(NULL) + 600;
+       while (serve_cache_loop(fd))
+               ; /* nothing */
+
+       close(fd);
+       unlink(socket_path);
+}
+
+static void check_socket_directory(const char *path)
+{
+       struct stat st;
+       char *path_copy = xstrdup(path);
+       char *dir = dirname(path_copy);
+
+       if (!stat(dir, &st)) {
+               free(path_copy);
+               return;
+       }
+
+       /*
+        * We must be sure to create the directory with the correct mode,
+        * not just chmod it after the fact; otherwise, there is a race
+        * condition in which somebody can chdir to it, sleep, then try to open
+        * our protected socket.
+        */
+       if (safe_create_leading_directories_const(dir) < 0)
+               die_errno("unable to create directories for '%s'", dir);
+       if (mkdir(dir, 0700) < 0)
+               die_errno("unable to mkdir '%s'", dir);
+       free(path_copy);
+}
+
+int main(int argc, const char **argv)
+{
+       setup_git_directory();
+       socket_path = git_pathdup("daemon/index");
+       check_socket_directory(socket_path);
+       atexit(cleanup_socket);
+       sigchain_push_common(cleanup_socket_on_signal);
+       serve_cache(socket_path);
+       return 0;
+}
-- 
1.9.1.346.ga2b5940

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