chrt: Add support for SCHED_FLAG_DL_OVERRUN

When set on a SCHED_DEADLINE task, the kernel sends SIGXCPU to the
task if it exceeds its runtime budget within a period. Without this
flag the task is silently throttled until the next period. Useful
for real-time applications that need to detect when they are not
meeting their timing requirements.

Add -O/--deadline-overrun option to allow users to toggle this
feature using the deadline scheduling class.

Signed-off-by: Furkan Caliskan <frn1furkan10@gmail.com>

diff --git a/bash-completion/chrt b/bash-completion/chrt
index 363efdfa1fb9e025fcfd3a8d7539edc10977520f..ead03b02377d5ac9d2d6eef7573b9fdea8798a93 100644 (file)
--- a/bash-completion/chrt
+++ b/bash-completion/chrt
@@ -19,6 +19,7 @@ _chrt_module()
                                --all-tasks
                                --batch
                                --deadline
+                               --deadline-overrun
                                --ext
                                --fifo
                                --help

diff --git a/schedutils/chrt.1.adoc b/schedutils/chrt.1.adoc
index 7c2ceab866f21f133de457b1da31f0ecea18c6b4..13a785c7e729e46708a860629f56bf4d991b0069 100644 (file)
--- a/schedutils/chrt.1.adoc
+++ b/schedutils/chrt.1.adoc
@@ -85,6 +85,9 @@ Specifies deadline parameter for *SCHED_DEADLINE* policy (Linux-specific).
 *-G*, *--reclaim-grub*::
 Enables GRUB (Greedy Reclamation of Unused Bandwidth) algorithm. Linux-specific, supported since 4.13.
 
+*-O*, *--deadline-overrun*::
+Set *SCHED_FLAG_DL_OVERRUN* to receive *SIGXCPU* when a *SCHED_DEADLINE* task exceeds its runtime budget within a period. Without this flag the task is silently throttled until the next period. Linux-specific, supported since 4.16.
+
 *-R*, *--reset-on-fork*::
 Use *SCHED_RESET_ON_FORK* or *SCHED_FLAG_RESET_ON_FORK* flag. Linux-specific, supported since 2.6.31.
 +

diff --git a/schedutils/chrt.c b/schedutils/chrt.c
index 6bf08c5c1a5c4cd70e5f7e0da3d741ef22aca6ea..cec41468ae702afcdd1431591deea968249f8242 100644 (file)
--- a/schedutils/chrt.c
+++ b/schedutils/chrt.c
@@ -93,6 +93,7 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(_("Scheduling options:\n"), out);
        fputs(_(" -R, --reset-on-fork       set reset-on-fork flag\n"), out);
        fputs(_(" -G, --reclaim-grub        set SCHED_FLAG_RECLAIM\n"), out);
+       fputs(_(" -O, --deadline-overrun    set SCHED_FLAG_DL_OVERRUN\n"), out);
        fputs(_(" -T, --sched-runtime <ns>  runtime parameter for DEADLINE\n"), out);
        fputs(_(" -P, --sched-period <ns>   period parameter for DEADLINE\n"), out);
        fputs(_(" -D, --sched-deadline <ns> deadline parameter for DEADLINE\n"), out);
@@ -440,6 +441,7 @@ int main(int argc, char **argv)
                { "all-tasks",  no_argument, NULL, 'a' },
                { "batch",      no_argument, NULL, 'b' },
                { "deadline",   no_argument, NULL, 'd' },
+               { "deadline-overrun", no_argument, NULL, 'O' },
                { "ext",        no_argument, NULL, 'e' },
                { "fifo",       no_argument, NULL, 'f' },
                { "idle",       no_argument, NULL, 'i' },
@@ -463,7 +465,7 @@ int main(int argc, char **argv)
        textdomain(PACKAGE);
        close_stdout_atexit();
 
-       while((c = getopt_long(argc, argv, "+abdD:efiphmoP:T:rRGvV", longopts, NULL)) != -1)
+       while((c = getopt_long(argc, argv, "+abdD:efiphmoOP:T:rRGvV", longopts, NULL)) != -1)
        {
                switch (c) {
                case 'a':
@@ -499,6 +501,11 @@ int main(int argc, char **argv)
                case 'G':
 #ifdef SCHED_FLAG_RECLAIM
                        ctl->sched_flags |= SCHED_FLAG_RECLAIM;
+#endif
+                       break;
+               case 'O':
+#ifdef SCHED_FLAG_DL_OVERRUN
+                       ctl->sched_flags |= SCHED_FLAG_DL_OVERRUN;
 #endif
                        break;
                case 'i':
@@ -596,6 +603,14 @@ int main(int argc, char **argv)
 #  endif
        if ((ctl->sched_flags & SCHED_FLAG_RECLAIM) && ctl->policy != SCHED_DEADLINE)
                errx(EXIT_FAILURE, _("--reclaim-grub is only supported for SCHED_DEADLINE"));
+# endif
+# ifdef SCHED_FLAG_DL_OVERRUN
+#  ifndef HAVE_SCHED_SETATTR
+       if (ctl->sched_flags & SCHED_FLAG_DL_OVERRUN)
+               errx(EXIT_FAILURE, _("SCHED_FLAG_DL_OVERRUN is unsupported"));
+#  endif
+       if ((ctl->sched_flags & SCHED_FLAG_DL_OVERRUN) && ctl->policy != SCHED_DEADLINE)
+               errx(EXIT_FAILURE, _("--deadline-overrun is only supported for SCHED_DEADLINE"));
 # endif
        if (ctl->policy == SCHED_DEADLINE) {
                /* The basic rule is runtime <= deadline <= period, so we can