[Pcsclite-git-commit] [PCSC] 03/06: Fix signal handler by using only allowed functions
Ludovic Rousseau
rousseau at moszumanska.debian.org
Sun Apr 24 17:08:31 UTC 2016
This is an automated email from the git hooks/post-receive script.
rousseau pushed a commit to branch master
in repository PCSC.
commit abe436e38aa58cb1140eff0d497ba721474c7703
Author: Ludovic Rousseau <ludovic.rousseau at free.fr>
Date: Sun Apr 24 18:46:53 2016 +0200
Fix signal handler by using only allowed functions
The signals are now treated in a special thread created just for that purpose.
Thanks to Andre Florath for the bug report
https://lists.alioth.debian.org/pipermail/pcsclite-muscle/Week-of-Mon-20160404/000561.html
[Pcsclite-muscle] pcscd jams when using '--auto-exit'
Andre Florath andre at florath.net
Sat Apr 9 06:06:44 UTC 2016
Hello!
Since some time I have problems with pcscd. I'm using pcscd in
conjunction with online banking and after a short period of working it
stops and jams the banking application.
A 'strace' to the pcscd showed that it is still running somewhere
deep in the USB stack.
The problem is, when manually running the the pcscd, there is no
problem at all - only when running from systemd.
Therefore I searched for the differences and found one: the
'--auto-exit'. Downloaded the source and had a closer look.
What I understand from the source code is, that when '--auto-exit' is
given, a SIGALRM is generated which (should) terminate the process.
I have noticed that the signal handler 'signal_trap()' uses some
function calls that are not allowed in signal handlers; like:
* syslog()
* gettimeofday()
* remove()
Using this creates undefined behavior.
(Please see 'man 7 signal' for a complete list of system calls that
are not allowed in signal handlers.)
I found a workaround for the issue.
Changed the service file to:
===
[Unit]
Description=PC/SC Smart Card Daemon
[Service]
ExecStart=/usr/sbin/pcscd --foreground --debug -a
ExecReload=/usr/sbin/pcscd --hotplug
[Install]
Also=pcscd.socket
===
and disabling the pcscd.socket gives me a stable system.
(Yes - pcscd is now started at boot time and runs the whole time
- which is fine for me.)
If you need more information, please drop me a note.
Kind regards
Andre
---
src/pcscdaemon.c | 170 ++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 111 insertions(+), 59 deletions(-)
diff --git a/src/pcscdaemon.c b/src/pcscdaemon.c
index 791f7f6..624e759 100644
--- a/src/pcscdaemon.c
+++ b/src/pcscdaemon.c
@@ -81,6 +81,7 @@ char SocketActivated = FALSE;
static int ExitValue = EXIT_FAILURE;
int HPForceReaderPolling = 0;
static int pipefd[] = {-1, -1};
+static int signal_handler_fd[] = {-1, -1};
char Add_Serial_In_Name = TRUE;
char Add_Interface_In_Name = TRUE;
@@ -89,7 +90,6 @@ char Add_Interface_In_Name = TRUE;
*/
static void at_exit(void);
static void clean_temp_files(void);
-static void signal_reload(int sig);
static void signal_trap(int);
static void print_version (void);
static void print_usage (char const * const);
@@ -152,6 +152,10 @@ static void SVCServiceRunLoop(void)
/* Nothing to do in case of a syscall interrupted
* It happens when SIGUSR1 (reload) or SIGINT (Ctrl-C) is received
* We just try again */
+
+ /* we wait a bit so that the signal handler thread can do
+ * its job and set AraKiri if needed */
+ SYS_USleep(1000);
break;
default:
@@ -162,6 +166,93 @@ static void SVCServiceRunLoop(void)
}
}
+/**
+ * thread dedicated to handle signals
+ *
+ * a signal handler can not call any function. See signal(7) for a list
+ * of function that are safe to call from a signal handler.
+ * The functions syslog(), gettimeofday() and remove() are NOT safe.
+ */
+static void *signal_thread(void *arg)
+{
+ (void)arg;
+
+ while (TRUE)
+ {
+ int r;
+ int sig;
+
+ r = read(signal_handler_fd[0], &sig, sizeof sig);
+ if (r < 0)
+ {
+ Log2(PCSC_LOG_ERROR, "read failed: %s", strerror(errno));
+ return NULL;
+ }
+
+ Log2(PCSC_LOG_INFO, "Received signal: %d", sig);
+
+ /* signal for hotplug */
+ if (SIGUSR1 == sig)
+ {
+#ifdef USE_USB
+ if (! AraKiri)
+ HPReCheckSerialReaders();
+#endif
+ /* Reenable the signal handler.
+ * This is needed on Solaris and HPUX. */
+ (void)signal(SIGUSR1, signal_trap);
+
+ continue;
+ }
+
+ /* do not wait if asked to terminate
+ * avoids waiting after the reader(s) in shutdown for example */
+ if (SIGTERM == sig)
+ {
+ Log1(PCSC_LOG_INFO, "Direct suicide");
+ at_exit();
+ }
+
+ if (SIGALRM == sig)
+ {
+ /* normal exit without error */
+ ExitValue = EXIT_SUCCESS;
+ }
+
+ /* the signal handler is called several times for the same Ctrl-C */
+ if (AraKiri == FALSE)
+ {
+ Log1(PCSC_LOG_INFO, "Preparing for suicide");
+ AraKiri = TRUE;
+
+ /* if still in the init/loading phase the AraKiri will not be
+ * seen by the main event loop
+ */
+ if (Init)
+ {
+ Log1(PCSC_LOG_INFO, "Suicide during init");
+ at_exit();
+ }
+ }
+ else
+ {
+ /* if pcscd do not want to die */
+ static int lives = 2;
+
+ lives--;
+ /* no live left. Something is blocking the normal death. */
+ if (0 == lives)
+ {
+ Log1(PCSC_LOG_INFO, "Forced suicide");
+ at_exit();
+ }
+ }
+ }
+
+ return NULL;
+}
+
+
int main(int argc, char **argv)
{
int rv;
@@ -515,6 +606,20 @@ int main(int argc, char **argv)
/* exits on SIGALARM to allow pcscd to suicide if not used */
(void)signal(SIGALRM, signal_trap);
+ if (pipe(signal_handler_fd) == -1)
+ {
+ Log2(PCSC_LOG_CRITICAL, "pipe() failed: %s", strerror(errno));
+ return EXIT_FAILURE;
+ }
+
+ pthread_t signal_handler_thread;
+ rv = pthread_create(&signal_handler_thread, NULL, signal_thread, NULL);
+ if (rv)
+ {
+ Log2(PCSC_LOG_CRITICAL, "pthread_create failed: %s", strerror(rv));
+ return EXIT_FAILURE;
+ }
+
/*
* If PCSCLITE_IPC_DIR does not exist then create it
*/
@@ -610,7 +715,7 @@ int main(int argc, char **argv)
/*
* Hotplug rescan
*/
- (void)signal(SIGUSR1, signal_reload);
+ (void)signal(SIGUSR1, signal_trap);
/*
* Initialize the comm structure
@@ -730,66 +835,13 @@ static void clean_temp_files(void)
strerror(errno));
}
-static void signal_reload(/*@unused@*/ int sig)
-{
- (void)signal(SIGUSR1, signal_reload);
-
- (void)sig;
-
- if (AraKiri)
- return;
-
-#ifdef USE_USB
- HPReCheckSerialReaders();
-#endif
-} /* signal_reload */
-
static void signal_trap(int sig)
{
- Log2(PCSC_LOG_INFO, "Received signal: %d", sig);
-
- /* do not wait if asked to terminate
- * avoids waiting after the reader(s) in shutdown for example */
- if (SIGTERM == sig)
- {
- Log1(PCSC_LOG_INFO, "Direct suicide");
- at_exit();
- }
-
- if (SIGALRM == sig)
- {
- /* normal exit without error */
- ExitValue = EXIT_SUCCESS;
- }
-
- /* the signal handler is called several times for the same Ctrl-C */
- if (AraKiri == FALSE)
- {
- Log1(PCSC_LOG_INFO, "Preparing for suicide");
- AraKiri = TRUE;
-
- /* if still in the init/loading phase the AraKiri will not be
- * seen by the main event loop
- */
- if (Init)
- {
- Log1(PCSC_LOG_INFO, "Suicide during init");
- at_exit();
- }
- }
- else
- {
- /* if pcscd do not want to die */
- static int lives = 2;
+ int r;
- lives--;
- /* no live left. Something is blocking the normal death. */
- if (0 == lives)
- {
- Log1(PCSC_LOG_INFO, "Forced suicide");
- at_exit();
- }
- }
+ r = write(signal_handler_fd[1], &sig, sizeof sig);
+ if (r < 0)
+ Log2(PCSC_LOG_ERROR, "write failed: %s", strerror(errno));
}
static void print_version (void)
--
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