linux-kernel - [PATCH] kdb: use ktime_get_seconds() instead of ktime_get

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Message-Id: <b3c1e952cfff95e0289772d6af5ec2ebd6cc3141.1516935110.git.baolin.wang@linaro.org>
Date:   Fri, 26 Jan 2018 11:03:14 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     jason.wessel@...driver.com, daniel.thompson@...aro.org
Cc:     baolin.wang@...aro.org, mingo@...nel.org, arnd@...db.de,
        broonie@...nel.org, kgdb-bugreport@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kdb: use ktime_get_seconds() instead of ktime_get_ts()

The kdb code will print the monotonic time by ktime_get_ts(), but
the ktime_get_ts() will be protected by a sequence lock, that will
introduce one deadlock risk if the lock was already held in the
context from which we entered the debugger.

Since kdb is only interested in the second field, we can use the
ktime_get_seconds() to get the monotonic time without a lock,
moreover we can remove the 'struct timespec', which is not y2038
safe.

Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
 kernel/debug/kdb/kdb_main.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 69e70f4..f0fc6f7 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2486,10 +2486,8 @@ static int kdb_kill(int argc, const char **argv)
  */
 static void kdb_sysinfo(struct sysinfo *val)
 {
-	struct timespec uptime;
-	ktime_get_ts(&uptime);
 	memset(val, 0, sizeof(*val));
-	val->uptime = uptime.tv_sec;
+	val->uptime = ktime_get_seconds();
 	val->loads[0] = avenrun[0];
 	val->loads[1] = avenrun[1];
 	val->loads[2] = avenrun[2];
-- 
1.7.9.5