Improve cancellations, randomness, and time

- Exhaustively document cancellation points
- Rename SIGCANCEL to SIGTHR just like BSDs
- Further improve POSIX thread cancellations
- Ensure asynchronous cancellations work correctly
- Elevate the quality of getrandom() and getentropy()
- Make futexes cancel correctly on OpenBSD 6.x and 7.x
- Add reboot.com and shutdown.com to examples directory
- Remove underscore prefix from awesome timespec_*() APIs
- Create assertions that help verify our cancellation points
- Remove bad timespec APIs (cmp generalizes eq/ne/gt/gte/lt/lte)

Author: jart

examples/clock.c

@@ -20,22 +20,22 @@ int main(int argc, char *argv[]) {
   volatile unsigned long x;
   struct timespec now, start, next, interval;
   printf("hammering the cpu...\n");
-  next = start = _timespec_mono();
-  interval = _timespec_frommillis(500);
-  next = _timespec_add(next, interval);
+  next = start = timespec_mono();
+  interval = timespec_frommillis(500);
+  next = timespec_add(next, interval);
   for (;;) {
     for (i = 0;; ++i) {
       x *= 7;
       if (!(i % 256)) {
-        now = _timespec_mono();
-        if (_timespec_gte(now, next)) {
+        now = timespec_mono();
+        if (timespec_cmp(now, next) >= 0) {
           break;
         }
       }
     }
-    next = _timespec_add(next, interval);
+    next = timespec_add(next, interval);
     printf("consumed %10g seconds monotonic time and %10g seconds cpu time\n",
-           _timespec_tonanos(_timespec_sub(now, start)) / 1000000000.,
+           timespec_tonanos(timespec_sub(now, start)) / 1000000000.,
            (double)clock() / CLOCKS_PER_SEC);
   }
 }

examples/clock_getres.c

@@ -28,7 +28,7 @@ void show(int clock) {
   }
   shown[n++] = clock;
   if (clock_getres(clock, &ts) != -1) {
-    kprintf("%s %'ld ns\n", DescribeClockName(clock), _timespec_tonanos(ts));
+    kprintf("%s %'ld ns\n", DescribeClockName(clock), timespec_tonanos(ts));
   } else {
     kprintf("%s %s\n", DescribeClockName(clock), _strerrno(errno));
   }

examples/reboot.c

@@ -0,0 +1,39 @@
+#if 0
+/*─────────────────────────────────────────────────────────────────╗
+│ To the extent possible under law, Justine Tunney has waived      │
+│ all copyright and related or neighboring rights to this file,    │
+│ as it is written in the following disclaimers:                   │
+│   • http://unlicense.org/                                        │
+│   • http://creativecommons.org/publicdomain/zero/1.0/            │
+╚─────────────────────────────────────────────────────────────────*/
+#endif
+#include "libc/calls/calls.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/reboot.h"
+
+int main(int argc, char *argv[]) {
+  char line[8] = {0};
+  if (argc > 1 && !strcmp(argv[1], "-y")) {
+    line[0] = 'y';
+  } else {
+    printf("reboot your computer? yes or no [no] ");
+    fflush(stdout);
+    fgets(line, sizeof(line), stdin);
+  }
+  if (line[0] == 'y' || line[0] == 'Y') {
+    if (reboot(RB_AUTOBOOT)) {
+      printf("system is rebooting...\n");
+      exit(0);
+    } else {
+      perror("reboot");
+      exit(1);
+    }
+  } else if (line[0] == 'n' || line[0] == 'N') {
+    exit(0);
+  } else {
+    printf("error: unrecognized response\n");
+    exit(2);
+  }
+}

examples/shutdown.c

@@ -0,0 +1,39 @@
+#if 0
+/*─────────────────────────────────────────────────────────────────╗
+│ To the extent possible under law, Justine Tunney has waived      │
+│ all copyright and related or neighboring rights to this file,    │
+│ as it is written in the following disclaimers:                   │
+│   • http://unlicense.org/                                        │
+│   • http://creativecommons.org/publicdomain/zero/1.0/            │
+╚─────────────────────────────────────────────────────────────────*/
+#endif
+#include "libc/calls/calls.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/reboot.h"
+
+int main(int argc, char *argv[]) {
+  char line[8] = {0};
+  if (argc > 1 && !strcmp(argv[1], "-y")) {
+    line[0] = 'y';
+  } else {
+    printf("shutdown your computer? yes or no [no] ");
+    fflush(stdout);
+    fgets(line, sizeof(line), stdin);
+  }
+  if (line[0] == 'y' || line[0] == 'Y') {
+    if (reboot(RB_POWER_OFF)) {
+      printf("system is shutting down...\n");
+      exit(0);
+    } else {
+      perror("reboot");
+      exit(1);
+    }
+  } else if (line[0] == 'n' || line[0] == 'N') {
+    exit(0);
+  } else {
+    printf("error: unrecognized response\n");
+    exit(2);
+  }
+}

libc/calls/_timespec_eq.c

@@ -7,13 +7,16 @@ COSMOPOLITAN_C_START_
 #define BLOCK_CANCELLATIONS \
   do {                      \
     int _CancelState;       \
-  pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &_CancelState)
+  _CancelState = _pthread_block_cancellations()
 
-#define ALLOW_CANCELLATIONS                \
-  pthread_setcancelstate(_CancelState, 0); \
-  }                                        \
+#define ALLOW_CANCELLATIONS                   \
+  _pthread_allow_cancellations(_CancelState); \
+  }                                           \
   while (0)
 
+int _pthread_block_cancellations(void);
+void _pthread_allow_cancellations(int);
+
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
 #endif /* COSMOPOLITAN_LIBC_CALLS_BLOCKCANCEL_H_ */