upload-pack: Use finish_{command,async}() instead of waitpid().

upload-pack spawns two processes, rev-list and pack-objects, and carefully
monitors their status so that it can report failure to the remote end.
This change removes the complicated procedures on the grounds of the
following observations:

- If everything is OK, rev-list closes its output pipe end, upon which
pack-objects (which reads from the pipe) sees EOF and terminates itself,
closing its output (and error) pipes. upload-pack reads from both until
it sees EOF in both. It collects the exit codes of the child processes
(which indicate success) and terminates successfully.

- If rev-list sees an error, it closes its output and terminates with
failure. pack-objects sees EOF in its input and terminates successfully.
Again upload-pack reads its inputs until EOF. When it now collects
the exit codes of its child processes, it notices the failure of rev-list
and signals failure to the remote end.

- If pack-objects sees an error, it terminates with failure. Since this
breaks the pipe to rev-list, rev-list is killed with SIGPIPE.
upload-pack reads its input until EOF, then collects the exit codes of
the child processes, notices their failures, and signals failure to the
remote end.

- If upload-pack itself dies unexpectedly, pack-objects is killed with
SIGPIPE, and subsequently also rev-list.

The upshot of this is that precise monitoring of child processes is not
required because both terminate if either one of them dies unexpectedly.
This allows us to use finish_command() and finish_async() instead of
an explicit waitpid(2) call.

The change is smaller than it looks because most of it only reduces the
indentation of a large part of the inner loop.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/t/t5530-upload-pack-error.sh b/t/t5530-upload-pack-error.sh
new file mode 100755 (executable)
index 0000000..cc8949e
--- /dev/null
+++ b/t/t5530-upload-pack-error.sh
@@ -0,0 +1,75 @@
+#!/bin/sh
+
+test_description='errors in upload-pack'
+
+. ./test-lib.sh
+
+D=`pwd`
+
+corrupt_repo () {
+       object_sha1=$(git rev-parse "$1") &&
+       ob=$(expr "$object_sha1" : "\(..\)") &&
+       ject=$(expr "$object_sha1" : "..\(..*\)") &&
+       rm -f ".git/objects/$ob/$ject"
+}
+
+test_expect_success 'setup and corrupt repository' '
+
+       echo file >file &&
+       git add file &&
+       git rev-parse :file &&
+       git commit -a -m original &&
+       test_tick &&
+       echo changed >file &&
+       git commit -a -m changed &&
+       corrupt_repo HEAD:file
+
+'
+
+test_expect_failure 'fsck fails' '
+
+       git fsck
+'
+
+test_expect_success 'upload-pack fails due to error in pack-objects' '
+
+       ! echo "0032want $(git rev-parse HEAD)
+00000009done
+0000" | git-upload-pack . > /dev/null 2> output.err &&
+       grep "pack-objects died" output.err
+'
+
+test_expect_success 'corrupt repo differently' '
+
+       git hash-object -w file &&
+       corrupt_repo HEAD^^{tree}
+
+'
+
+test_expect_failure 'fsck fails' '
+
+       git fsck
+'
+test_expect_success 'upload-pack fails due to error in rev-list' '
+
+       ! echo "0032want $(git rev-parse HEAD)
+00000009done
+0000" | git-upload-pack . > /dev/null 2> output.err &&
+       grep "waitpid (async) failed" output.err
+'
+
+test_expect_success 'create empty repository' '
+
+       mkdir foo &&
+       cd foo &&
+       git init
+
+'
+
+test_expect_failure 'fetch fails' '
+
+       git fetch .. master
+
+'
+
+test_done

diff --git a/upload-pack.c b/upload-pack.c
index 67994680f2f48e573f78c592c853422e6d8995cf..7e04311027176fc87c1de7dd619000d2a75d4eb9 100644 (file)
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -144,6 +144,7 @@ static void create_pack_file(void)
        char abort_msg[] = "aborting due to possible repository "
                "corruption on the remote side.";
        int buffered = -1;
+       ssize_t sz;
        const char *argv[10];
        int arg = 0;
 
@@ -168,22 +169,15 @@ static void create_pack_file(void)
        pack_objects.git_cmd = 1;
        pack_objects.argv = argv;
 
-       if (start_command(&pack_objects)) {
-               /* daemon sets things up to ignore TERM */
-               kill(rev_list.pid, SIGKILL);
+       if (start_command(&pack_objects))
                die("git-upload-pack: unable to fork git-pack-objects");
-       }
 
        /* We read from pack_objects.err to capture stderr output for
         * progress bar, and pack_objects.out to capture the pack data.
         */
 
        while (1) {
-               const char *who;
                struct pollfd pfd[2];
-               pid_t pid;
-               int status;
-               ssize_t sz;
                int pe, pu, pollsize;
 
                reset_timeout();
@@ -204,123 +198,91 @@ static void create_pack_file(void)
                        pollsize++;
                }
 
-               if (pollsize) {
-                       if (poll(pfd, pollsize, -1) < 0) {
-                               if (errno != EINTR) {
-                                       error("poll failed, resuming: %s",
-                                             strerror(errno));
-                                       sleep(1);
-                               }
-                               continue;
-                       }
-                       if (0 <= pu && (pfd[pu].revents & (POLLIN|POLLHUP))) {
-                               /* Data ready; we keep the last byte
-                                * to ourselves in case we detect
-                                * broken rev-list, so that we can
-                                * leave the stream corrupted.  This
-                                * is unfortunate -- unpack-objects
-                                * would happily accept a valid pack
-                                * data with trailing garbage, so
-                                * appending garbage after we pass all
-                                * the pack data is not good enough to
-                                * signal breakage to downstream.
-                                */
-                               char *cp = data;
-                               ssize_t outsz = 0;
-                               if (0 <= buffered) {
-                                       *cp++ = buffered;
-                                       outsz++;
-                               }
-                               sz = xread(pack_objects.out, cp,
-                                         sizeof(data) - outsz);
-                               if (0 < sz)
-                                               ;
-                               else if (sz == 0) {
-                                       close(pack_objects.out);
-                                       pack_objects.out = -1;
-                               }
-                               else
-                                       goto fail;
-                               sz += outsz;
-                               if (1 < sz) {
-                                       buffered = data[sz-1] & 0xFF;
-                                       sz--;
-                               }
-                               else
-                                       buffered = -1;
-                               sz = send_client_data(1, data, sz);
-                               if (sz < 0)
-                                       goto fail;
-                       }
-                       if (0 <= pe && (pfd[pe].revents & (POLLIN|POLLHUP))) {
-                               /* Status ready; we ship that in the side-band
-                                * or dump to the standard error.
-                                */
-                               sz = xread(pack_objects.err, progress,
-                                         sizeof(progress));
-                               if (0 < sz)
-                                       send_client_data(2, progress, sz);
-                               else if (sz == 0) {
-                                       close(pack_objects.err);
-                                       pack_objects.err = -1;
-                               }
-                               else
-                                       goto fail;
+               if (!pollsize)
+                       break;
+
+               if (poll(pfd, pollsize, -1) < 0) {
+                       if (errno != EINTR) {
+                               error("poll failed, resuming: %s",
+                                     strerror(errno));
+                               sleep(1);
                        }
+                       continue;
                }
-
-               /* See if the children are still there */
-               if (rev_list.pid || pack_objects.pid) {
-                       pid = waitpid(-1, &status, WNOHANG);
-                       if (!pid)
-                               continue;
-                       who = ((pid == rev_list.pid) ? "git-rev-list" :
-                              (pid == pack_objects.pid) ? "git-pack-objects" :
-                              NULL);
-                       if (!who) {
-                               if (pid < 0) {
-                                       error("git-upload-pack: %s",
-                                             strerror(errno));
-                                       goto fail;
-                               }
-                               error("git-upload-pack: we weren't "
-                                     "waiting for %d", pid);
-                               continue;
+               if (0 <= pu && (pfd[pu].revents & (POLLIN|POLLHUP))) {
+                       /* Data ready; we keep the last byte to ourselves
+                        * in case we detect broken rev-list, so that we
+                        * can leave the stream corrupted.  This is
+                        * unfortunate -- unpack-objects would happily
+                        * accept a valid packdata with trailing garbage,
+                        * so appending garbage after we pass all the
+                        * pack data is not good enough to signal
+                        * breakage to downstream.
+                        */
+                       char *cp = data;
+                       ssize_t outsz = 0;
+                       if (0 <= buffered) {
+                               *cp++ = buffered;
+                               outsz++;
+                       }
+                       sz = xread(pack_objects.out, cp,
+                                 sizeof(data) - outsz);
+                       if (0 < sz)
+                                       ;
+                       else if (sz == 0) {
+                               close(pack_objects.out);
+                               pack_objects.out = -1;
                        }
-                       if (!WIFEXITED(status) || WEXITSTATUS(status) > 0) {
-                               error("git-upload-pack: %s died with error.",
-                                     who);
+                       else
                                goto fail;
+                       sz += outsz;
+                       if (1 < sz) {
+                               buffered = data[sz-1] & 0xFF;
+                               sz--;
                        }
-                       if (pid == rev_list.pid)
-                               rev_list.pid = 0;
-                       if (pid == pack_objects.pid)
-                               pack_objects.pid = 0;
-                       if (rev_list.pid || pack_objects.pid)
-                               continue;
-               }
-
-               /* both died happily */
-               if (pollsize)
-                       continue;
-
-               /* flush the data */
-               if (0 <= buffered) {
-                       data[0] = buffered;
-                       sz = send_client_data(1, data, 1);
+                       else
+                               buffered = -1;
+                       sz = send_client_data(1, data, sz);
                        if (sz < 0)
                                goto fail;
-                       fprintf(stderr, "flushed.\n");
                }
-               if (use_sideband)
-                       packet_flush(1);
-               return;
+               if (0 <= pe && (pfd[pe].revents & (POLLIN|POLLHUP))) {
+                       /* Status ready; we ship that in the side-band
+                        * or dump to the standard error.
+                        */
+                       sz = xread(pack_objects.err, progress,
+                                 sizeof(progress));
+                       if (0 < sz)
+                               send_client_data(2, progress, sz);
+                       else if (sz == 0) {
+                               close(pack_objects.err);
+                               pack_objects.err = -1;
+                       }
+                       else
+                               goto fail;
+               }
+       }
+
+       if (finish_command(&pack_objects)) {
+               error("git-upload-pack: git-pack-objects died with error.");
+               goto fail;
+       }
+       if (finish_async(&rev_list))
+               goto fail;      /* error was already reported */
+
+       /* flush the data */
+       if (0 <= buffered) {
+               data[0] = buffered;
+               sz = send_client_data(1, data, 1);
+               if (sz < 0)
+                       goto fail;
+               fprintf(stderr, "flushed.\n");
        }
+       if (use_sideband)
+               packet_flush(1);
+       return;
+
  fail:
-       if (pack_objects.pid)
-               kill(pack_objects.pid, SIGKILL);
-       if (rev_list.pid)
-               kill(rev_list.pid, SIGKILL);
        send_client_data(3, abort_msg, sizeof(abort_msg));
        die("git-upload-pack: %s", abort_msg);
 }