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repo-add: Avoid race condition in signal handlers

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There is a small chance that a user sends SIGINT (or any other signal
that is trapped) when we're already in clean_up() which used to lead to
trap_exit() being executed and the remaining code in clean_up() being
skipped due to the bash signal/trap handler blocking EXIT (since its
handler is already being executed, even if it's interrupted).

In practice, this behaviour caused unexpected results (primarily because
pressing ^C at the wrong time left a lock file behind):

    $ ./repo-add extra.db.tar.gz foobar
    ==> Extracting database to a temporary location...
    ^C
    ==> ERROR: Aborted by user! Exiting...
    $ ./repo-add extra.db.tar.gz foobar
    ==> Extracting database to a temporary location...
    ==> ERROR: File 'foobar' not found.
    ==> No packages modified, nothing to do.
    ^C
    ==> ERROR: Aborted by user! Exiting...
    $ ./repo-add extra.db.tar.gz foobar
    ==> ERROR: Failed to acquire lockfile: extra.db.tar.gz.lck.
    ==> ERROR: Held by process 18522

Fix this and reduce the chance of race conditions in signal handlers by:

* Unhooking all traps in both clean_up() and trap_exit().

* Call clean_up() explicitly in trap_exit() to make sure we remove the
  lock file and the temporary directory even if we send SIGINT when
  clean_up() is already being executed but didn't reach the unhook code
  yet.

Also, add an optional parameter to clean_up() to allow for setting an
explicit exit code when we call clean_up() from trap_exit().

Signed-off-by: Lukas Fleischer <archlinux@cryptocrack.de>
Signed-off-by: Dan McGee <dan@archlinux.org>
This commit is contained in:
Lukas Fleischer 2011-10-13 17:23:19 +02:00 committed by Dan McGee
parent 12642a299b
commit d4c97ea2f6
1 changed files with 8 additions and 2 deletions
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10
scripts/repo-add.sh.in
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@ -520,13 +520,19 @@ remove() {
} }
trap_exit() { trap_exit() {
# unhook all traps to avoid race conditions
trap '' EXIT TERM HUP QUIT INT ERR
echo echo
error "$@" error "$@"
exit 1 clean_up 1
} }
clean_up() { clean_up() {
local exit_code=$? local exit_code=${1:-$?}
# unhook all traps to avoid race conditions
trap '' EXIT TERM HUP QUIT INT ERR
[[ -d $tmpdir ]] && rm -rf "$tmpdir" [[ -d $tmpdir ]] && rm -rf "$tmpdir"
(( CLEAN_LOCK )) && [[ -f $LOCKFILE ]] && rm -f "$LOCKFILE" (( CLEAN_LOCK )) && [[ -f $LOCKFILE ]] && rm -f "$LOCKFILE"