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-rw-r--r--src/xz/mytime.c56
-rw-r--r--src/xz/mytime.h6
-rw-r--r--src/xz/private.h12
-rw-r--r--src/xz/signals.c17
4 files changed, 89 insertions, 2 deletions
diff --git a/src/xz/mytime.c b/src/xz/mytime.c
index 7e8a0749..0b0e2be7 100644
--- a/src/xz/mytime.c
+++ b/src/xz/mytime.c
@@ -20,7 +20,12 @@
uint64_t opt_flush_timeout = 0;
+#ifdef USE_SIGTSTP_HANDLER
+static volatile uint64_t start_time;
+#else
static uint64_t start_time;
+#endif
+
static uint64_t next_flush;
@@ -48,10 +53,49 @@ mytime_now(void)
}
+#ifdef USE_SIGTSTP_HANDLER
+extern void
+mytime_sigtstp_handler(int sig lzma_attribute((__unused__)))
+{
+ // Measure how long the process stays in the stopped state and add
+ // that amount to start_time. This way the the progress indicator
+ // won't count the stopped time as elapsed time and the estimated
+ // remaining time won't be confused by the time spent in the
+ // stopped state.
+ //
+ // FIXME? Is raising SIGSTOP the correct thing to do? POSIX.1-2017
+ // says that orphan processes shouldn't stop on SIGTSTP. So perhaps
+ // the most correct thing to do could be to revert to the default
+ // handler for SIGTSTP, unblock SIGTSTP, and then raise(SIGTSTP).
+ // It's quite a bit more complicated than just raising SIGSTOP though.
+ //
+ // The difference between raising SIGTSTP vs. SIGSTOP can be seen on
+ // the shell command line too by running "echo $?" after stopping
+ // a process but perhaps that doesn't matter.
+ const uint64_t t = mytime_now();
+ raise(SIGSTOP);
+ start_time += mytime_now() - t;
+ return;
+}
+#endif
+
+
extern void
mytime_set_start_time(void)
{
+#ifdef USE_SIGTSTP_HANDLER
+ // Block the signals when accessing start_time so that we cannot
+ // end up with a garbage value. start_time is volatile but access
+ // to it isn't atomic at least on 32-bit systems.
+ signals_block();
+#endif
+
start_time = mytime_now();
+
+#ifdef USE_SIGTSTP_HANDLER
+ signals_unblock();
+#endif
+
return;
}
@@ -59,7 +103,17 @@ mytime_set_start_time(void)
extern uint64_t
mytime_get_elapsed(void)
{
- return mytime_now() - start_time;
+#ifdef USE_SIGTSTP_HANDLER
+ signals_block();
+#endif
+
+ const uint64_t t = mytime_now() - start_time;
+
+#ifdef USE_SIGTSTP_HANDLER
+ signals_unblock();
+#endif
+
+ return t;
}
diff --git a/src/xz/mytime.h b/src/xz/mytime.h
index a7be2aa7..5a3c1e21 100644
--- a/src/xz/mytime.h
+++ b/src/xz/mytime.h
@@ -21,6 +21,12 @@
extern uint64_t opt_flush_timeout;
+#ifdef USE_SIGTSTP_HANDLER
+/// \brief Signal handler for SIGTSTP
+extern void mytime_sigtstp_handler(int sig);
+#endif
+
+
/// \brief Store the time when (de)compression was started
///
/// The start time is also stored as the time of the first flush.
diff --git a/src/xz/private.h b/src/xz/private.h
index 6414bdb5..a20dbc57 100644
--- a/src/xz/private.h
+++ b/src/xz/private.h
@@ -49,6 +49,18 @@
# define ENABLE_SANDBOX 1
#endif
+// Handling SIGTSTP keeps time-keeping for progress indicator correct
+// if xz is stopped. It requires use of clock_gettime() as that is
+// async-signal safe in POSIX. Require also SIGALRM support since
+// on systems where SIGALRM isn't available, progress indicator code
+// polls the time and the SIGTSTP handling adds slight overhead to
+// that code. Most (all?) systems that have SIGTSTP also have SIGALRM
+// so this requirement won't exclude many systems.
+#if defined(HAVE_CLOCK_GETTIME) && defined(HAVE_CLOCK_MONOTONIC) \
+ && defined(SIGTSTP) && defined(SIGALRM)
+# define USE_SIGTSTP_HANDLER 1
+#endif
+
#include "main.h"
#include "mytime.h"
#include "coder.h"
diff --git a/src/xz/signals.c b/src/xz/signals.c
index 7aef463c..ff42a396 100644
--- a/src/xz/signals.c
+++ b/src/xz/signals.c
@@ -82,6 +82,11 @@ signals_init(void)
sigaddset(&hooked_signals, message_progress_sigs[i]);
#endif
+#ifdef USE_SIGTSTP_HANDLER
+ // Add the SIGTSTP handler from mytime.c to hooked_signals.
+ sigaddset(&hooked_signals, SIGTSTP);
+#endif
+
// Using "my_sa" because "sa" may conflict with a sockaddr variable
// from system headers on Solaris.
struct sigaction my_sa;
@@ -96,10 +101,11 @@ signals_init(void)
my_sa.sa_flags = 0;
my_sa.sa_handler = &signal_handler;
+ struct sigaction old;
+
for (size_t i = 0; i < ARRAY_SIZE(sigs); ++i) {
// If the parent process has left some signals ignored,
// we don't unignore them.
- struct sigaction old;
if (sigaction(sigs[i], NULL, &old) == 0
&& old.sa_handler == SIG_IGN)
continue;
@@ -109,6 +115,15 @@ signals_init(void)
message_signal_handler();
}
+#ifdef USE_SIGTSTP_HANDLER
+ if (!(sigaction(SIGTSTP, NULL, &old) == 0
+ && old.sa_handler == SIG_IGN)) {
+ my_sa.sa_handler = &mytime_sigtstp_handler;
+ if (sigaction(SIGTSTP, &my_sa, NULL))
+ message_signal_handler();
+ }
+#endif
+
signals_are_initialized = true;
return;