tail -f again follows changes to a file after it's renamed.
[bug introduced in coreutils-7.5]
+ tail --follow no longer misses changes to files if those files were
+ replaced before inotify watches were created.
+ [bug introduced in coreutils-7.5]
+
** New features
chroot accepts the new --skip-chdir option to not change the working directory
# define fremote(fd, name) false
#endif
-/* FIXME: describe */
-
+/* open/fstat F->name and handle changes. */
static void
recheck (struct File_spec *f, bool blocking)
{
- /* open/fstat the file and announce if dev/ino have changed */
struct stat new_stats;
bool ok = true;
bool is_stdin = (STREQ (f->name, "-"));
return spec1->wd == spec2->wd;
}
-/* Helper function used by 'tail_forever_inotify'. */
+/* Output (new) data for FSPEC->fd. */
static void
check_fspec (struct File_spec *fspec, int wd, int *prev_wd)
{
tail_forever_inotify (int wd, struct File_spec *f, size_t n_files,
double sleep_interval)
{
+# if TAIL_TEST_SLEEP
+ /* Delay between open() and inotify_add_watch()
+ to help trigger different cases. */
+ xnanosleep (1000000);
+# endif
unsigned int max_realloc = 3;
/* Map an inotify watch descriptor to the name of the file it's watching. */
Hash_table *wd_to_name;
bool found_watchable_file = false;
+ bool tailed_but_unwatchable = false;
bool found_unwatchable_dir = false;
bool no_inotify_resources = false;
bool writer_is_dead = false;
if (f[i].wd < 0)
{
+ if (f[i].fd != -1) /* already tailed. */
+ tailed_but_unwatchable = true;
if (errno == ENOSPC || errno == ENOMEM)
{
no_inotify_resources = true;
/* Linux kernel 2.6.24 at least has a bug where eventually, ENOSPC is always
returned by inotify_add_watch. In any case we should revert to polling
when there are no inotify resources. Also a specified directory may not
- be currently present or accessible, so revert to polling. */
- if (no_inotify_resources || found_unwatchable_dir)
+ be currently present or accessible, so revert to polling. Also an already
+ tailed but unwatchable due rename/unlink race, should also revert. */
+ if (no_inotify_resources || found_unwatchable_dir
+ || (follow_mode == Follow_descriptor && tailed_but_unwatchable))
{
hash_free (wd_to_name);
prev_wd = f[n_files - 1].wd;
- /* Check files again. New data can be available since last time we checked
- and before they are watched by inotify. */
+ /* Check files again. New files or data can be available since last time we
+ checked and before they are watched by inotify. */
for (i = 0; i < n_files; i++)
{
- if (!f[i].ignore)
- check_fspec (&f[i], f[i].wd, &prev_wd);
+ if (! f[i].ignore)
+ {
+ /* check for new files. */
+ if (follow_mode == Follow_name)
+ recheck (&(f[i]), false);
+ else if (f[i].fd != -1)
+ {
+ /* If the file was replaced in the small window since we tailed,
+ then assume the watch is on the wrong item (different to
+ that we've already produced output for), and so revert to
+ polling the original descriptor. */
+ struct stat stats;
+
+ if (stat (f[i].name, &stats) == 0
+ && (f[i].dev != stats.st_dev || f[i].ino != stats.st_ino))
+ {
+ error (0, errno, _("%s was replaced"),
+ quote (pretty_name (&(f[i]))));
+ hash_free (wd_to_name);
+
+ errno = 0;
+ return true;
+ }
+ }
+
+ /* check for new data. */
+ check_fspec (&f[i], f[i].wd, &prev_wd);
+ }
}
evlen += sizeof (struct inotify_event) + 1;
{
struct stat stats;
-#if TEST_RACE_BETWEEN_FINAL_READ_AND_INITIAL_FSTAT
+#if TAIL_TEST_SLEEP
/* Before the tail function provided 'read_pos', there was
a race condition described in the URL below. This sleep
call made the window big enough to exercise the problem. */
if (fflush (stdout) != 0)
error (EXIT_FAILURE, errno, _("write error"));
- if (!tail_forever_inotify (wd, F, n_files, sleep_interval))
+ if (! tail_forever_inotify (wd, F, n_files, sleep_interval))
return EXIT_FAILURE;
}
error (0, errno, _("inotify cannot be used, reverting to polling"));
all_tests = \
tests/misc/help-version.sh \
tests/tail-2/inotify-race.sh \
+ tests/tail-2/inotify-race2.sh \
tests/misc/invalid-opt.pl \
tests/rm/ext3-perf.sh \
tests/rm/cycle.sh \
--- /dev/null
+#!/bin/sh
+# Ensure that tail does not ignore a tailed-forever file that has been
+# replaced between tail's initial read-to-EOF, and when the inotify watches
+# are established in tail_forever_inotify. That new file would be ignored
+# indefinitely.
+
+# Copyright (C) 2015 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# 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, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ tail
+
+# Terminate any background gdb/tail process
+cleanup_() {
+ kill $pid 2>/dev/null && wait $pid
+ kill $sleep 2>/dev/null && wait $sleep
+}
+
+touch file || framework_failure_
+touch tail.out || framework_failure_
+
+( timeout 10s gdb --version ) > gdb.out 2>&1
+case $(cat gdb.out) in
+ *'GNU gdb'*) ;;
+ *) skip_ "can't run gdb";;
+esac
+
+# Break on a line rather than a symbol, to cater for inline functions
+break_src="$abs_top_srcdir/src/tail.c"
+break_line=$(grep -n ^tail_forever_inotify "$break_src") || framework_failure_
+break_line=$(echo "$break_line" | cut -d: -f1) || framework_failure_
+
+
+# Note we get tail to monitor a background sleep process
+# rather than using timeout(1), as timeout sends SIGCONT
+# signals to its monitored process, and gdb (7.9 at least)
+# has _intermittent_ issues with this.
+# Sending SIGCONT resulted in either delayed child termination,
+# or no child termination resulting in a hung test.
+# See https://sourceware.org/bugzilla/show_bug.cgi?id=18364
+
+env sleep 10 & sleep=$!
+
+# See if gdb works and
+# tail_forever_inotify is compiled and run
+gdb -nx --batch-silent \
+ --eval-command="break $break_line" \
+ --eval-command="run --pid=$sleep -f file" \
+ --eval-command='quit' \
+ tail < /dev/null > gdb.out 2>&1
+
+kill $sleep || skip_ 'breakpoint not hit'
+wait $sleep
+
+# FIXME: The above is seen to _intermittently_ fail with:
+# warning: .dynamic section for "/lib/libc.so.6" is not at the expected address
+# warning: difference appears to be caused by prelink, adjusting expectations
+compare /dev/null gdb.out || skip_ "can't set breakpoints in tail"
+
+env sleep 10 & sleep=$!
+
+echo never-seen-with-tail-8.23 > file.new || framework_failure_
+
+# Run "tail -F file", stopping to replace with a new file before
+# inotify initialization, and then continue. Before the fix,
+# changes to the new file would effectively be ignored.
+gdb -nx --batch-silent \
+ --eval-command="break $break_line" \
+ --eval-command="run --pid=$sleep -F file 2>tail.err >>tail.out" \
+ --eval-command='shell mv file.new file' \
+ --eval-command='continue' \
+ --eval-command='quit' \
+ tail < /dev/null > /dev/null 2>&1 & pid=$!
+
+# Note even updating the watched 'file' wouldn't have output
+# anything between coreutils 7.5 and 8.23 inclusive as
+# The old file descriptor (still held open by tail) was being fstat().
+
+tail --pid=$pid -f tail.out | (read; kill $pid)
+
+# gdb has a bug in Debian's gdb-6.8-3 at least that causes it to not
+# cleanup and exit correctly when it receives a SIGTERM, but
+# killing sleep, should cause the tail process and thus gdb to exit.
+kill $sleep
+wait $sleep
+
+wait $pid
+
+compare /dev/null tail.out && { cat tail.err; fail=1; }
+
+Exit $fail
grep '^#define HAVE_INOTIFY 1' "$CONFIG_HEADER" >/dev/null \
|| skip_ 'inotify required'
-require_strace_ inotify_rm_watch
+require_strace_ 'inotify_add_watch,inotify_rm_watch'
+
+# Quickly skip on remote file systems
+df --local . >/dev/null 2>&1 ||
+ skip_ 'inotify not used on remote file system'
check_tail_output()
{
# however without it strace will ignore SIGTERM.
# strace does always honor SIGTERM with the -I2 option,
# though that's not available on RHEL6 for example.
-timeout 180 strace -e inotify_rm_watch -o strace.out \
+timeout 180 strace -e inotify_add_watch,inotify_rm_watch -o strace.out \
tail -F $fastpoll k >> out 2>&1 & pid=$!
reverted_to_polling_=0
echo $i
echo 'tailed' > k;
- # wait for 'tailed' in (after first iteration; new) file and then in 'out'
- grep_timeout 'tailed' || { cleanup_fail 'failed to find "tailed"'; break; }
+
+ # Wait for watch on (new) file
+ strace_re='inotify_add_watch.*MODIFY' retry_delay_ check_strace .1 8 ||
+ no_watch_=1
+
+ # Assume this is not because we're leaking
+ # (resources may already be depleted)
+ # The explicit check for inotify_rm_watch should confirm that.
+ grep -F 'reverting to polling' out >/dev/null && skip_ 'inotify unused'
+
+ # Otherwise failure is unknown
+ test "$no_watch_" && { cat out; framework_failure_ 'no inotify_add_watch'; }
mv k k.tmp
# wait for tail to detect the rename
grep_timeout 'inaccessible' ||
{ cleanup_fail 'failed to detect rename'; break; }
- # Assume this is not because we're leaking.
- # The explicit check for inotify_rm_watch should confirm that.
- grep -F 'reverting to polling' out >/dev/null &&
- { reverted_to_polling_=1; break; }
-
# Note we strace here rather than consuming all available watches
# to be more efficient, but more importantly avoid depleting resources.
# Note also available resources can currently be tuned with:
>out && >strace.out || framework_failure_ 'failed to reset output files'
done
-test "$reverted_to_polling_" = 1 && skip_ 'inotify resources already depleted'
-
cleanup_
Exit $fail
projects / thirdparty / coreutils.git / commitdiff
