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signals: better nesting support

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Support upto 3 levels os nesting signal blocking.
As of today - code blocks signals immediatelly when it opens
VG in read-write mode - this however makes current prompt usage
then partially unusable since user may not 'break' command
during prompt (something most user would expect).

Until a better fix for prompting is implemented, put in support
for signal nesting - thus when prompt enables signal acceptance,
make it possible to really break command at this point.
This commit is contained in:
Zdenek Kabelac 2014-05-02 17:30:27 +02:00
parent 31ac200a37
commit e585a6bbcf
2 changed files with 15 additions and 21 deletions
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1
WHATS_NEW
View File

@ -1,5 +1,6 @@
Version 2.02.107 -
==================================
Better support for nesting of blocking signals.
Use only sigaction handler and drop duplicate signal handler.
Separate signal handling and flock code out into lib/misc.
Don't start dmeventd checking seg_monitor and monitoring is disabled.

35
lib/misc/lvm-signal.c
View File

@ -21,9 +21,12 @@
static sigset_t _oldset;
static int _signals_blocked = 0;
static volatile sig_atomic_t _sigint_caught = 0;
static volatile sig_atomic_t _handler_installed2;
static struct sigaction _oldhandler2;
static int _oldmasked;
static volatile sig_atomic_t _handler_installed;
/* Support 3 level nesting, increase if needed more */
#define MAX_SIGINTS 3
static struct sigaction _oldhandler[MAX_SIGINTS];
static int _oldmasked[MAX_SIGINTS];
static void _catch_sigint(int unused __attribute__((unused)))
{
@ -61,10 +64,8 @@ void sigint_allow(void)
* Do not overwrite the backed-up handler data -
* just increase nesting count.
*/
if (_handler_installed2) {
_handler_installed2++;
if (++_handler_installed >= MAX_SIGINTS)
return;
}
/* Grab old sigaction for SIGINT: shall not fail. */
if (sigaction(SIGINT, NULL, &handler))
@ -73,17 +74,15 @@ void sigint_allow(void)
handler.sa_flags &= ~SA_RESTART; /* Clear restart flag */
handler.sa_handler = _catch_sigint;
_handler_installed2 = 1;
/* Override the signal handler: shall not fail. */
if (sigaction(SIGINT, &handler, &_oldhandler2))
if (sigaction(SIGINT, &handler, &_oldhandler[_handler_installed - 1]))
log_sys_debug("sigaction", "SIGINT");
/* Unmask SIGINT. Remember to mask it again on restore. */
if (sigprocmask(0, NULL, &sigs))
log_sys_debug("sigprocmask", "");
if ((_oldmasked = sigismember(&sigs, SIGINT))) {
if ((_oldmasked[_handler_installed] = sigismember(&sigs, SIGINT))) {
sigdelset(&sigs, SIGINT);
if (sigprocmask(SIG_SETMASK, &sigs, NULL))
log_sys_debug("sigprocmask", "SIG_SETMASK");
@ -92,18 +91,12 @@ void sigint_allow(void)
void sigint_restore(void)
{
if (!_handler_installed2)
if (!_handler_installed ||
--_handler_installed >= MAX_SIGINTS)
return;
if (_handler_installed2 > 1) {
_handler_installed2--;
return;
}
/* Nesting count went down to 0. */
_handler_installed2 = 0;
if (_oldmasked) {
/* Nesting count went bellow MAX_SIGINTS. */
if (_oldmasked[_handler_installed]) {
sigset_t sigs;
sigprocmask(0, NULL, &sigs);
sigaddset(&sigs, SIGINT);
@ -111,7 +104,7 @@ void sigint_restore(void)
log_sys_debug("sigprocmask", "SIG_SETMASK");
}
if (sigaction(SIGINT, &_oldhandler2, NULL))
if (sigaction(SIGINT, &_oldhandler[_handler_installed], NULL))
log_sys_debug("sigaction", "SIGINT restore");
}