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Re: [PATCH] tail: add comments noting potential inotify-related problems
From: |
Giuseppe Scrivano |
Subject: |
Re: [PATCH] tail: add comments noting potential inotify-related problems |
Date: |
Fri, 03 Jul 2009 00:06:39 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.0.95 (gnu/linux) |
Hi Jim,
I took a look at the problems you reported. The first one is fixed with
the first attached patch.
I have tested it under Linux 2.6.18-6-xen-686.
tail -F works until the parent directory is not removed and it is very
related to the second problem you showed. At this point I think the
best way is to find a solution to both, using a tree instead of a hash
map. What do you think?
Thanks,
Giuseppe
Jim Meyering <address@hidden> writes:
> Hi Giuseppe,
>
> I noticed two potential problems.
> The first appears to affects only kernels 2.6.13..2.6.20.
> The second one doesn't have to be fixed before the upcoming release.
>From 8fbe1d2d1f666a0428f41d03831e18d4d1b56e89 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Thu, 2 Jul 2009 23:38:46 +0200
Subject: [PATCH 1/2] tail: avoid a problem for kernels prior to 2.6.21
* src/tail.c (tail_forever_inotify): Handle the special case that the
inotify watcher returns zero bytes.
---
src/tail.c | 7 ++++---
1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/src/tail.c b/src/tail.c
index 89c43b8..a99091a 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1259,8 +1259,9 @@ tail_forever_inotify (int wd, struct File_spec *f, int
n_files)
evbuf_off = 0;
/* For kernels prior to 2.6.21, read returns 0 when the buffer
- is too small. FIXME: handle that. */
- if (len == SAFE_READ_ERROR && errno == EINVAL && max_realloc--)
+ is too small. */
+ if ((len == 0 || (len == SAFE_READ_ERROR && errno == EINVAL)) &&
+ max_realloc--)
{
len = 0;
evlen *= 2;
@@ -1268,7 +1269,7 @@ tail_forever_inotify (int wd, struct File_spec *f, int
n_files)
continue;
}
- if (len == SAFE_READ_ERROR)
+ if (len == SAFE_READ_ERROR || len == 0)
error (EXIT_FAILURE, errno, _("error reading inotify event"));
}
--
1.6.3.3
>From bfbd6a82055326ea45882664890a5e77aa3bb2a1 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Thu, 2 Jul 2009 23:40:40 +0200
Subject: [PATCH 2/2] tail: fixed a test case
* tests/tail-2/wait: Be sure the `not_accessible' file is really not
accessible before try to "tail -f" it.
---
tests/tail-2/wait | 23 +++++++++++++----------
1 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/tests/tail-2/wait b/tests/tail-2/wait
index 7eee8b1..8f2f610 100755
--- a/tests/tail-2/wait
+++ b/tests/tail-2/wait
@@ -45,17 +45,20 @@ if test -n "$state"; then
kill $pid
fi
-tail -s0.1 -f not_accessible &
-pid=$!
-sleep .5
-state=$(get_process_status_ $pid)
-
-if test -n "$state"; then
- case $state in
- S*) echo $0: process still active 1>&2; fail=1 ;;
- *) ;;
- esac
- kill $pid
+# Check if the file is really not accessible before use it.
+if ! cat not_accessible; then
+ tail -s0.1 -f not_accessible &
+ pid=$!
+ sleep .5
+ state=$(get_process_status_ $pid)
+
+ if test -n "$state"; then
+ case $state in
+ S*) echo $0: process still active 1>&2; fail=1 ;;
+ *) ;;
+ esac
+ kill $pid
+ fi
fi
(tail -s0.1 -f here 2>tail.err) &
--
1.6.3.3
- Re: [PATCH] tail: add comments noting potential inotify-related problems,
Giuseppe Scrivano <=