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diff --git a/lib/libthr/libthr.3 b/lib/libthr/libthr.3
--- a/lib/libthr/libthr.3
+++ b/lib/libthr/libthr.3
@@ -216,6 +216,12 @@
.Xr _umtx_op
for more details.
The default value is large enough for most useful applications.
+.It Dv kern.ipc.umtx_min_timeout
+The minimal amount of time, in nanoseconds, the thread is required to sleep
+for pthread operations specifying a timeout.
+If the operation requests a timeout less than the value of the MIB,
+it is silently increased to the value.
+The value of zero means no limit.
.It Dv debug.umtx.robust_faults_verbose
A non zero value makes kernel emit some diagnostic when the robust
mutexes unlock was prematurely aborted after detecting some inconsistency,
diff --git a/sys/kern/kern_umtx.c b/sys/kern/kern_umtx.c
--- a/sys/kern/kern_umtx.c
+++ b/sys/kern/kern_umtx.c
@@ -151,6 +151,26 @@
&umtx_max_rb, 0,
"Maximum number of robust mutexes allowed for each thread");
+static sbintime_t umtx_min_timeout;
+static int
+sysctl_umtx_min_timeout(SYSCTL_HANDLER_ARGS)
+{
+ int error, val;
+
+ val = sbttons(umtx_min_timeout);
+ error = sysctl_handle_int(oidp, &val, 0, req);
+ if (error != 0 || req->newptr == NULL)
+ return (error);
+ if (val < 0)
+ return (EINVAL);
+ umtx_min_timeout = nstosbt(val);
+ return (0);
+}
+SYSCTL_PROC(_kern_ipc, OID_AUTO, umtx_min_timeout,
+ CTLFLAG_RW | CTLTYPE_UINT | CTLFLAG_MPSAFE, NULL, 0,
+ sysctl_umtx_min_timeout, "U",
+ "Minimal timeout for umtx in nanoseconds");
+
static uma_zone_t umtx_pi_zone;
static struct umtxq_chain umtxq_chains[2][UMTX_CHAINS];
static MALLOC_DEFINE(M_UMTX, "umtx", "UMTX queue memory");
@@ -700,6 +720,18 @@
(umtxtime->_flags & UMTX_ABSTIME) != 0, &umtxtime->_timeout);
}
+static void
+umtx_abs_timeout_enforce_min(sbintime_t *sbt)
+{
+ sbintime_t when;
+
+ if (__predict_false(umtx_min_timeout != 0)) {
+ when = sbinuptime() + umtx_min_timeout;
+ if (*sbt < when)
+ *sbt = when;
+ }
+}
+
static int
umtx_abs_timeout_getsbt(struct umtx_abs_timeout *timo, sbintime_t *sbt,
int *flags)
@@ -739,6 +771,7 @@
return (0);
}
*sbt = bttosbt(bt);
+ umtx_abs_timeout_enforce_min(sbt);
/*
* Check if the absolute time should be aligned to

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