Blocking command with a 0.001 seconds timeout blocks indefinitely (#11688)

Any value in the range of [0-1) turns to 0 when being cast from double to long long. This change rounds up instead of down for values that can't be stored precisely as long doubles.

(cherry picked from commit eef29b68a2cd94de1f03aa1b7891af75f5cabae2)

2 files changed, 13 insertions, 1 deletions

diff --git a/src/timeout.c b/src/timeout.c
index 36cea7c26..90d0fe796 100644
--- a/src/timeout.c
+++ b/src/timeout.c
@@ -29,6 +29,8 @@
 #include "server.h"
 #include "cluster.h"
 
+#include <math.h>
+
 /* ========================== Clients timeouts ============================= */
 
 /* Check if this blocked client timedout (does nothing if the client is
@@ -169,7 +171,7 @@ int getTimeoutFromObjectOrReply(client *c, robj *object, mstime_t *timeout, int
         if (getLongDoubleFromObjectOrReply(c,object,&ftval,
             "timeout is not a float or out of range") != C_OK)
             return C_ERR;
-        tval = (long long) (ftval * 1000.0);
+        tval = (long long) ceill(ftval * 1000.0);
     } else {
         if (getLongLongFromObjectOrReply(c,object,&tval,
             "timeout is not an integer or out of range") != C_OK)
diff --git a/tests/unit/type/list.tcl b/tests/unit/type/list.tcl
index 3133923d6..0c52dd8f5 100644
--- a/tests/unit/type/list.tcl
+++ b/tests/unit/type/list.tcl
@@ -1256,6 +1256,16 @@ foreach {pop} {BLPOP BLMPOP_LEFT} {
             $rd close
         }
 
+        test "$pop: with 0.001 timeout should not block indefinitely" {
+            # Use a timeout of 0.001 and wait for the number of blocked clients to equal 0.
+            # Validate the empty read from the deferring client.
+            set rd [redis_deferring_client]
+            bpop_command $rd $pop blist1 0.001
+            wait_for_blocked_clients_count 0
+            assert_equal {} [$rd read]
+            $rd close
+        }
+
         test "$pop: second argument is not a list" {
             set rd [redis_deferring_client]
             r del blist1{t} blist2{t}