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fix signal handling (#1073698)

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This commit is contained in:
Nils Philippsen 2014-03-19 14:32:01 +01:00
parent e92b2b861f
commit 59a0b0a864
2 changed files with 227 additions and 0 deletions
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220
xsane-0.999-signal-handling.patch Normal file
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@ -0,0 +1,220 @@
From 54a700c45c81f1ffff5f3dfcecb3929143e31d48 Mon Sep 17 00:00:00 2001
From: Nils Philippsen <nils@redhat.com>
Date: Wed, 19 Mar 2014 13:23:16 +0100
Subject: [PATCH] patch: signal-handling
Squashed commit of the following:
commit 2b629e1d9c60dcf26defe6d05b515611874db270
Author: Nils Philippsen <nils@redhat.com>
Date: Thu Mar 13 13:38:12 2014 +0100
separate signal handlers in top and bottom half
This is to avoid race-conditions occurring when a signal is received
while the signal handler is not yet finished. It also avoids calling
non-reentrant functions from a signal handler. The top half (the real
signal handler) just writes a character into a pipe which gets picked up
and serviced by the bottom half from the normal event loop, this
serializes things and makes use of non-reentrant functions safe.
---
src/xsane.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 131 insertions(+), 15 deletions(-)
diff --git a/src/xsane.c b/src/xsane.c
index eee76ff..02b4da4 100644
--- a/src/xsane.c
+++ b/src/xsane.c
@@ -47,6 +47,7 @@
#endif
#include <sys/wait.h>
+#include <glib-unix.h>
#include <stdarg.h>
@@ -121,6 +122,7 @@ static const Preferences_medium_t pref_default_medium[]=
int DBG_LEVEL = 0;
static guint xsane_resolution_timer = 0;
+static int xsane_signal_pipe[2];
/* ---------------------------------------------------------------------------------------------------------------------- */
@@ -161,8 +163,11 @@ void xsane_pref_save(void);
static int xsane_pref_restore(void);
static void xsane_pref_save_media(void);
static void xsane_pref_restore_media(void);
-static RETSIGTYPE xsane_quit_handler(int signal);
-static RETSIGTYPE xsane_sigchld_handler(int signal);
+static RETSIGTYPE xsane_signal_handler_top_half(int signal);
+static gboolean xsane_signal_handler_bottom_half(gint fd,
+ GIOCondition condition,
+ gpointer user_data);
+static void xsane_sigchld_handler(void);
static void xsane_quit(void);
static void xsane_exit(void);
static gint xsane_standard_option_win_delete(GtkWidget *widget, gpointer data);
@@ -2296,16 +2301,119 @@ static void xsane_pref_restore_media(void)
/* ---------------------------------------------------------------------------------------------------------------------- */
-static RETSIGTYPE xsane_quit_handler(int signal)
+static RETSIGTYPE xsane_signal_handler_top_half(int signal)
{
- DBG(DBG_proc, "xsane_quit_handler\n");
+ const char *msg_func = "xsane_signal_handler_top_half(): ";
+ const char *msg_short_write = "Short write() while processing signal.\n";
+ const char *msg_err = "Error during write().\n";
+ char sig_char;
+ ssize_t written;
+ int errno_saved = errno;
- xsane_quit();
+ switch (signal)
+ {
+ case SIGTERM:
+ sig_char = 't';
+ break;
+ case SIGINT:
+ sig_char = 'i';
+ break;
+ case SIGHUP:
+ sig_char = 'h';
+ break;
+ case SIGCHLD:
+ sig_char = 'c';
+ break;
+ default:
+ sig_char = '?';
+ break;
+ }
+
+ if ((written = write(xsane_signal_pipe[1], &sig_char, 1)) <= 0)
+ {
+ /* At this point, all bets are off. Salvage what we can. */
+
+ const char *msg = (written == 0) ? msg_short_write : msg_err;
+
+ if ((write(STDERR_FILENO, msg_func, strlen(msg_func)) < 0) ||
+ (write(STDERR_FILENO, msg, strlen(msg)) < 0))
+ {
+ /* This is really a no-op, but at this point it doesn't really matter
+ * anymore if the writes succeeded or not. */
+ goto bail_out;
+ }
+
+bail_out:
+ /* Ignore SIGCHLD errors, zombie processes don't hurt that much. */
+ if (signal != SIGCHLD)
+ {
+ struct SIGACTION act;
+ memset(&act, 0, sizeof(act));
+ act.sa_handler = SIG_DFL;
+ sigaction(signal, &act, NULL);
+ raise(signal);
+ }
+ }
+
+ errno = errno_saved;
+}
+
+static gboolean xsane_signal_handler_bottom_half(gint fd,
+ GIOCondition condition,
+ gpointer user_data)
+{
+ char sig_char;
+ ssize_t readlen;
+
+ DBG(DBG_proc, "xsane_signal_handler_bottom_half\n");
+
+ while ((readlen = read(xsane_signal_pipe[0], &sig_char, 1)) != 0)
+ {
+ if (readlen < 0)
+ {
+ if (errno == EINTR)
+ {
+ /* if interrupted by signal, just repeat reading */
+ continue;
+ }
+ else
+ {
+ break;
+ }
+ }
+
+ switch (sig_char)
+ {
+ case 't':
+ case 'i':
+ case 'h':
+ xsane_quit();
+ break;
+ case 'c':
+ xsane_sigchld_handler();
+ break;
+ default:
+ DBG(DBG_error,
+ "Don't know how to cope with character-encoded signal: '%c'\n",
+ sig_char);
+ break;
+ }
+ }
+
+ /* previous invocation might have read more than it should, so ignore
+ * EGAIN/EWOULDBLOCK */
+ if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK)
+ {
+ DBG(DBG_error, "Error while reading from pipe: %d '%s'\n", errno,
+ strerror(errno));
+ }
+
+ return TRUE;
}
/* ---------------------------------------------------------------------------------------------------------------------- */
-static RETSIGTYPE xsane_sigchld_handler(int signal)
+static void xsane_sigchld_handler(void)
{
int status;
XsaneChildprocess **childprocess_listptr = &xsane.childprocess_list;
@@ -6062,18 +6170,26 @@ void xsane_interface(int argc, char **argv)
}
}
+ if (!g_unix_open_pipe(xsane_signal_pipe, FD_CLOEXEC, NULL) ||
+ fcntl(xsane_signal_pipe[0], F_SETFL, O_NONBLOCK, 1) ||
+ fcntl(xsane_signal_pipe[1], F_SETFL, O_NONBLOCK, 1) ||
+ !g_unix_fd_add(xsane_signal_pipe[0], G_IO_IN | G_IO_PRI,
+ xsane_signal_handler_bottom_half, NULL))
+ {
+ DBG(DBG_error,
+ "Couldn't create signal handling pipe, set flags on it or install\n"
+ "bottom half of handler.\n");
+ exit(1);
+ }
+
/* define SIGTERM, SIGINT, SIGHUP-handler to make sure that e.g. all temporary files are deleted */
/* when xsane gets such a signal */
memset(&act, 0, sizeof(act));
- act.sa_handler = xsane_quit_handler;
- sigaction(SIGTERM, &act, 0);
- sigaction(SIGINT, &act, 0);
- sigaction(SIGHUP, &act, 0);
-
- /* add a signal handler that cleans up zombie child processes */
- memset(&act, 0, sizeof(act));
- act.sa_handler = xsane_sigchld_handler;
- sigaction(SIGCHLD, &act, 0);
+ act.sa_handler = xsane_signal_handler_top_half;
+ sigaction(SIGTERM, &act, NULL);
+ sigaction(SIGINT, &act, NULL);
+ sigaction(SIGHUP, &act, NULL);
+ sigaction(SIGCHLD, &act, NULL);
gtk_main();
sane_exit();
--
1.8.5.3

7
xsane.spec
View File

@ -61,6 +61,9 @@ Patch11: xsane-0.999-pdf-no-high-bpp.patch
# build against lcms 2.x # build against lcms 2.x
# submitted to upstream (Oliver Rauch) via email, 2013-09-23 # submitted to upstream (Oliver Rauch) via email, 2013-09-23
Patch12: xsane-0.999-lcms2.patch Patch12: xsane-0.999-lcms2.patch
# fix signal handling (#1073698)
# submitted to upstream (Oliver Rauch) via email, 2014-03-19
Patch13: xsane-0.999-signal-handling.patch
# autoconf-generated files # autoconf-generated files
Patch100: xsane-0.999-7-autoconf.patch.bz2 Patch100: xsane-0.999-7-autoconf.patch.bz2
License: GPLv2+ License: GPLv2+
@ -126,6 +129,7 @@ done
%patch10 -p1 -b .man-page %patch10 -p1 -b .man-page
%patch11 -p1 -b .pdf-no-high-bpp %patch11 -p1 -b .pdf-no-high-bpp
%patch12 -p1 -b .lcms2 %patch12 -p1 -b .lcms2
%patch13 -p1 -b .signal-handling
%patch100 -p1 -b .autoconf %patch100 -p1 -b .autoconf
@ -230,6 +234,9 @@ fi
%{_datadir}/sane/xsane %{_datadir}/sane/xsane
%changelog %changelog
* Wed Mar 19 2014 Nils Philippsen <nils@redhat.com>
- fix signal handling (#1073698)
* Mon Sep 23 2013 Nils Philippsen <nils@redhat.com> - 0.999-7 * Mon Sep 23 2013 Nils Philippsen <nils@redhat.com> - 0.999-7
- get rid of ancient compat cruft - get rid of ancient compat cruft
- build against lcms2 - build against lcms2