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sheel: improve comments on signal handling

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2017-08-04 14:28:16 +02:00
parent 3346b4afc5
commit 49e6bf2db9
4 changed files with 45 additions and 17 deletions
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27
shell/ash.c
View File

@@ -3536,9 +3536,12 @@ setsignal(int signo)
#endif
}
}
//TODO: if !rootshell, we reset SIGQUIT to DFL,
//whereas we have to restore it to what shell got on entry
//from the parent. See comment above
/* if !rootshell, we reset SIGQUIT to DFL,
* whereas we have to restore it to what shell got on entry.
* This is handled by the fact that if signal was IGNored on entry,
* then cur_act is S_HARD_IGN and we never change its sigaction
* (see code below).
*/
if (signo == SIGCHLD)
new_act = S_CATCH;
@@ -3566,6 +3569,8 @@ setsignal(int signo)
if (cur_act == S_HARD_IGN || cur_act == new_act)
return;
*t = new_act;
act.sa_handler = SIG_DFL;
switch (new_act) {
case S_CATCH:
@@ -3575,16 +3580,13 @@ setsignal(int signo)
act.sa_handler = SIG_IGN;
break;
}
/* flags and mask matter only if !DFL and !IGN, but we do it
* for all cases for more deterministic behavior:
*/
act.sa_flags = 0;
act.sa_flags = 0; //TODO: why not SA_RESTART?
sigfillset(&act.sa_mask);
sigaction_set(signo, &act);
*t = new_act;
}
/* mode flags for set_curjob */
@@ -13429,7 +13431,9 @@ readcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
INT_ON;
if ((uintptr_t)r == 1 && errno == EINTR) {
/* to get SIGCHLD: sleep 1 & read x; echo $x */
/* To get SIGCHLD: sleep 1 & read x; echo $x
* Correct behavior is to not exit "read"
*/
if (pending_sig == 0)
goto again;
}
@@ -13544,13 +13548,14 @@ exitshell(void)
/* NOTREACHED */
}
static void
/* Don't inline: conserve stack of caller from having our locals too */
static NOINLINE void
init(void)
{
/* we will never free this */
basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ);
sigmode[SIGCHLD - 1] = S_DFL;
sigmode[SIGCHLD - 1] = S_DFL; /* ensure we install handler even if it is SIG_IGNed */
setsignal(SIGCHLD);
/* bash re-enables SIGHUP which is SIG_IGNed on entry.
@@ -13561,7 +13566,6 @@ init(void)
{
char **envp;
const char *p;
struct stat st1, st2;
initvar();
for (envp = environ; envp && *envp; envp++) {
@@ -13587,6 +13591,7 @@ init(void)
#endif
p = lookupvar("PWD");
if (p) {
struct stat st1, st2;
if (p[0] != '/' || stat(p, &st1) || stat(".", &st2)
|| st1.st_dev != st2.st_dev || st1.st_ino != st2.st_ino
) {

7
shell/hush.c
View File

@@ -1979,6 +1979,9 @@ static int check_and_run_traps(void)
break;
#if ENABLE_HUSH_JOB
case SIGHUP: {
//TODO: why are we doing this? ash and dash don't do this,
//they have no handler for SIGHUP at all,
//they rely on kernel to send SIGHUP+SIGCONT to orphaned process groups
struct pipe *job;
debug_printf_exec("%s: sig:%d default SIGHUP handler\n", __func__, sig);
/* bash is observed to signal whole process groups,
@@ -8646,6 +8649,10 @@ static void install_sighandlers(unsigned mask)
*/
if (sig == SIGCHLD)
continue;
/* bash re-enables SIGHUP which is SIG_IGNed on entry.
* Try: "trap '' HUP; bash; echo RET" and type "kill -HUP $$"
*/
//if (sig == SIGHUP) continue; - TODO?
if (old_handler == SIG_IGN) {
/* oops... restore back to IGN, and record this fact */
install_sighandler(sig, old_handler);