From: Dmitry V. Levin <ldv@altlinux.org>
Date: Fri, 23 Mar 2018 00:20:33 +0000 (+0000)
Subject: strace: further optimize unblocking of the delay signal handler
X-Git-Tag: v4.22~60
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5c0896d9d80df3b725f28fc1f1b5348c5f4a70a6;p=strace

strace: further optimize unblocking of the delay signal handler

Do not unblock the delay signal handler unless the delay timer is armed.

* defs.h (is_delay_timer_created): Remove.
(is_delay_timer_armed, delay_timer_expired): New prototypes.
* delay.c (delay_timer_is_armed): New static variable.
(is_delay_timer_created): Add static qualifier.
(is_delay_timer_armed, delay_timer_expired): New functions.
(arm_delay_timer): Set delay_timer_is_armed.
* strace.c (next_event): Use is_delay_timer_armed instead of
is_delay_timer_created to check whether the delay signal handler
has to be unblocked.
(timer_sighandler): Invoke delay_timer_expired.
---

diff --git a/defs.h b/defs.h
index ef135528..3899dd3d 100644
--- a/defs.h
+++ b/defs.h
@@ -1026,7 +1026,8 @@ extern struct inject_opts *inject_vec[SUPPORTED_PERSONALITIES];
 
 uint16_t alloc_delay_data(void);
 void fill_delay_data(uint16_t delay_idx, int intval, bool isenter);
-bool is_delay_timer_created(void);
+bool is_delay_timer_armed(void);
+void delay_timer_expired(void);
 void arm_delay_timer(const struct tcb *);
 void delay_tcb(struct tcb *, uint16_t delay_idx, bool isenter);
 
diff --git a/delay.c b/delay.c
index 8adf4cc5..86dd828e 100644
--- a/delay.c
+++ b/delay.c
@@ -37,6 +37,7 @@ static size_t delay_data_vec_capacity; /* size of the arena */
 static size_t delay_data_vec_size;     /* size of the used arena */
 
 static timer_t delay_timer = (timer_t) -1;
+static bool delay_timer_is_armed;
 
 static void
 expand_delay_data_vec(void)
@@ -80,12 +81,24 @@ fill_delay_data(uint16_t delay_idx, int intval, bool isenter)
 	ts->tv_nsec = intval % 1000000 * 1000;
 }
 
-bool
+static bool
 is_delay_timer_created(void)
 {
 	return delay_timer != (timer_t) -1;
 }
 
+bool
+is_delay_timer_armed(void)
+{
+	return delay_timer_is_armed;
+}
+
+void
+delay_timer_expired(void)
+{
+	delay_timer_is_armed = false;
+}
+
 void
 arm_delay_timer(const struct tcb *const tcp)
 {
@@ -96,6 +109,8 @@ arm_delay_timer(const struct tcb *const tcp)
 	if (timer_settime(delay_timer, TIMER_ABSTIME, &its, NULL))
 		perror_msg_and_die("timer_settime");
 
+	delay_timer_is_armed = true;
+
 	debug_func_msg("timer set to %lld.%09ld for pid %d",
 		       (long long) tcp->delay_expiration_time.tv_sec,
 		       (long) tcp->delay_expiration_time.tv_nsec,
diff --git a/strace.c b/strace.c
index 16b1a864..1493e9d9 100644
--- a/strace.c
+++ b/strace.c
@@ -2236,7 +2236,7 @@ next_event(int *pstatus, siginfo_t *si)
 			return TE_BREAK;
 	}
 
-	const bool unblock_delay_timer = is_delay_timer_created();
+	const bool unblock_delay_timer = is_delay_timer_armed();
 
 	/*
 	 * The window of opportunity to handle expirations
@@ -2607,6 +2607,8 @@ restart_delayed_tcbs(void)
 static void
 timer_sighandler(int sig)
 {
+	delay_timer_expired();
+
 	if (restart_failed)
 		return;