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[cadcdev-svn-commits] [SCM] branch master updated. v2.0.0-1065-gf4ccdac
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From: ljsebald <ljs...@us...> - 2023-09-15 19:41:15
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the project "A pseudo Operating System for the Dreamcast.".
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- Log -----------------------------------------------------------------
commit f4ccdacf521f130f7daddc488d7e81b1ed1a5a48
Author: Falco Girgis <gyr...@gm...>
Date: Fri Sep 15 14:40:22 2023 -0500
Initial C11 libatomic GCC builtin implementation (#301)
* Initial C99 libatomic GCC builtin implementation
- Initial implementation should cover everything C99 atomics entail,
located at kernel/libc/c11/atomics.c
* Update CHANGELOG
Typo. C99 atomics => C11 atomics.
* Began work on C11 atomics example/test.
- Added /kos/examples/dreamcast/basic/threading/atomic
- Currently have compile-time sanity checks, thread spawning, and
atomics declaration
- Still have to do actual atomic operations
* Fleshed out atomics test more, reporting lockless
- Exercising every major atomic and operation type in unit tests
- Actively yielding and sleeping threads in the middle of messing with
atomics, to encourage preemption for testing
- Modified __atomic_is_lock_free() to return TRUE, as the builtin
atomics from -matomic-model=soft-imask are all reporting at
compile-time as lock-free... meaning this implementation of C11 atomics
(interrupt toggling) is considered to be lock-free.
* Finalized atomics tests. All passing.
* Spinlock used for generic atomics, testbed update
- Swapped generic atomics to use spinlocks
* created a hash table of spinlocks mapping the atomic pointers to
specific locks based on their address range
- Updated example
* doing a lot more operations on the atomic buffer to ensure the
scheduler gets a chance to preempt and screw things up if the
implmentation is broken
* More comments, final code cleanup.
- Added more comments around the atomics back-end
- Removed a few comments from the example which were no longer relevant
* Fixed atomic_is_lock_free() for generic case
- Since we're using spinlocks to implement it, the generic atomics case
is no longer considered lock-free. Updated the back-end and example to
reflect this.
- Fixed a warning due to not making the pointer arg to
atomic_is_lock_free() volatile.
* Apply suggestions from code review
Co-authored-by: Lawrence Sebald <ljs...@us...>
* Apply suggestions from code review
Co-authored-by: Lawrence Sebald <ljs...@us...>
* Tiny formatting change missed in review.
* Update atomics.c
Forgot to make the thread function static. :)
---------
Co-authored-by: Lawrence Sebald <ljs...@us...>
commit 949ae95e0ce73195006a220dd9859da485fe8ed3
Author: Falco Girgis <gyr...@gm...>
Date: Fri Sep 15 14:39:03 2023 -0500
Added posix/sysconf.c to implement sysconf() (#306)
* Added posix/sysconf.c to implement sysconf()
- Implemented very basic functionality for POSIX function, sysconf(),
located within kos/kernel/libc/posix/sysconf.c
- Handling the following:
1. host name size
2. clock tick rate
3. maximum open files
4. page size + physical page count
5. available physical pages (approximate)
6. # of processors available/configured
* Added newline character
* Fixed #define used for maximum file descriptors
- Also reversed the sign of the EINVAL value returned for invalid name
parameters.
-----------------------------------------------------------------------
Summary of changes:
doc/CHANGELOG | 1 +
examples/dreamcast/basic/threading/Makefile | 6 +-
.../threading/{spinlock_test => atomics}/Makefile | 11 +-
.../dreamcast/basic/threading/atomics/atomics.c | 401 +++++++++++++++++++++
kernel/libc/c11/Makefile | 2 +-
kernel/libc/c11/atomics.c | 221 ++++++++++++
kernel/libc/posix/Makefile | 2 +-
kernel/libc/posix/sysconf.c | 43 +++
8 files changed, 678 insertions(+), 9 deletions(-)
copy examples/dreamcast/basic/threading/{spinlock_test => atomics}/Makefile (72%)
create mode 100644 examples/dreamcast/basic/threading/atomics/atomics.c
create mode 100644 kernel/libc/c11/atomics.c
create mode 100644 kernel/libc/posix/sysconf.c
diff --git a/doc/CHANGELOG b/doc/CHANGELOG
index 9072e76..d00c6d1 100644
--- a/doc/CHANGELOG
+++ b/doc/CHANGELOG
@@ -188,6 +188,7 @@ KallistiOS version 2.1.0 -----------------------------------------------
- *** Move definition of __RESTRICT from <sys/_types.h> to <kos/cdefs.h> [LS]
- DC Added DMA YUV converter path. Adjust some name of related #defines.
Added yuv examples [AB]
+- *** Added GCC builtin functions for supporting all of C11 atomics [FG]
KallistiOS version 2.0.0 -----------------------------------------------
- DC Broadband Adapter driver fixes [Megan Potter == MP]
diff --git a/examples/dreamcast/basic/threading/Makefile b/examples/dreamcast/basic/threading/Makefile
index fd7482f..91f63df 100644
--- a/examples/dreamcast/basic/threading/Makefile
+++ b/examples/dreamcast/basic/threading/Makefile
@@ -1,7 +1,7 @@
# KallistiOS ##version##
#
# examples/dreamcast/basic/threading/Makefile
-# (c)2002 Megan Potter
+# Copyright (C) 2002 Megan Potter
#
all:
@@ -11,6 +11,7 @@ all:
$(KOS_MAKE) -C once
$(KOS_MAKE) -C tls
$(KOS_MAKE) -C spinlock_test
+ $(KOS_MAKE) -C atomics
clean:
$(KOS_MAKE) -C general clean
@@ -19,6 +20,7 @@ clean:
$(KOS_MAKE) -C once clean
$(KOS_MAKE) -C tls clean
$(KOS_MAKE) -C spinlock_test clean
+ $(KOS_MAKE) -C atomics clean
dist:
$(KOS_MAKE) -C general dist
@@ -27,4 +29,4 @@ dist:
$(KOS_MAKE) -C once dist
$(KOS_MAKE) -C tls dist
$(KOS_MAKE) -C spinlock_test dist
-
+ $(KOS_MAKE) -C atomics dist
diff --git a/examples/dreamcast/basic/threading/spinlock_test/Makefile b/examples/dreamcast/basic/threading/atomics/Makefile
similarity index 72%
copy from examples/dreamcast/basic/threading/spinlock_test/Makefile
copy to examples/dreamcast/basic/threading/atomics/Makefile
index 403f45f..abc5d02 100644
--- a/examples/dreamcast/basic/threading/spinlock_test/Makefile
+++ b/examples/dreamcast/basic/threading/atomics/Makefile
@@ -1,12 +1,12 @@
# KallistiOS ##version##
#
-# basic/threading/spinlock_test/Makefile
-#
+# basic/threading/atomics/Makefile
# Copyright (C) 2023 Falco Girgis
#
-TARGET = spinlock_test.elf
-OBJS = spinlock_test.o
+TARGET = atomics.elf
+OBJS = atomics.o
+KOS_CFLAGS += -std=c11
all: rm-elf $(TARGET)
@@ -18,7 +18,7 @@ clean: rm-elf
rm-elf:
-rm -f $(TARGET)
-$(TARGET): $(OBJS)
+$(TARGET): $(OBJS)
kos-cc -o $(TARGET) $(OBJS)
run: $(TARGET)
@@ -27,3 +27,4 @@ run: $(TARGET)
dist: $(TARGET)
-rm -f $(OBJS)
$(KOS_STRIP) $(TARGET)
+
diff --git a/examples/dreamcast/basic/threading/atomics/atomics.c b/examples/dreamcast/basic/threading/atomics/atomics.c
new file mode 100644
index 0000000..156638e
--- /dev/null
+++ b/examples/dreamcast/basic/threading/atomics/atomics.c
@@ -0,0 +1,401 @@
+/* KallistiOS ##version##
+
+ examples/dreamcast/basic/threading/atomics.c
+
+ Copyright (C) 2023 Falco Girgis
+
+ This file serves as both an example of and a validation test for the
+ C11 atomics support provided by the SH-GCC toolchain and KOS. It
+ demonstrates advanced compiler-aware concurrency in pure standard C.
+
+ C11 atomics are an extremely convenient, easy-to-use concurrency
+ primitive supported at the language-level. They allow for thread-safe
+ access to and manipulation of variables without requiring an external
+ mutex or synchronization primitive to prevent multiple threads from
+ trying to modify the data simultaneously.
+
+ Atomics are also more efficient spatially on Dreamcast, because there is
+ no extra memory used for such additional mutexes to confer thread-safety
+ around such variables. In terms of runtime, they are implemented similarly
+ to mutexes, where interrupts are disabled around load/store/fetch operations.
+
+ Most of the back-end for atomics is provided by the compiler when using the
+ "-matomic-model=soft-imask" flag; however, KOS has to implement some of the
+ back-end for primitive types (64-bit types in particular) and generic structs.
+
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <threads.h>
+#include <stdatomic.h>
+
+/* Test that the standard library advertises that we even have atomics. */
+#ifdef __STDC_NO_ATOMICS__
+# error "The standard lib claims we don't support atomics!"
+#endif
+
+/* Test our compile-time macros for sanity. These can be used to detect
+ atomic locking characteristics at compile-time for your platform.
+ 0: The atomic type is never lock-free
+ 1: the atomic type is sometimes lock-free
+ 2: The atomic type is always lock-free
+*/
+_Static_assert(ATOMIC_BOOL_LOCK_FREE == 2,
+ "Our booleans are expected to be lock free!");
+_Static_assert(ATOMIC_CHAR_LOCK_FREE == 2,
+ "Our chars are expected to be lock free!");
+_Static_assert(ATOMIC_SHORT_LOCK_FREE == 2,
+ "Our shorts are expected to be lock free!");
+_Static_assert(ATOMIC_INT_LOCK_FREE == 2,
+ "Our ints are expected to be lock free!");
+_Static_assert(ATOMIC_LONG_LOCK_FREE == 2,
+ "Our longs are expected to be lock free!");
+_Static_assert(ATOMIC_POINTER_LOCK_FREE == 2,
+ "Our pointers are expected to be lock free!");
+_Static_assert(ATOMIC_LLONG_LOCK_FREE == 1,
+ "Our long longs are expected to sometimes be lock free!");
+
+#define THREAD_COUNT 20 /* # of threads to spawn */
+#define ITERATION_COUNT 5 /* # of times to iterate over each atomic */
+#define BUFFER_SIZE 4096 /* # of bytes in atomic buffer */
+#define BUFFER_UPDATE_COUNT 100 /* # of times to update atomic buffer */
+
+_Static_assert(THREAD_COUNT * ITERATION_COUNT <= UINT8_MAX,
+ "Threads * iterations would overflow uint8_t counters!");
+
+/* Generic buffer structure we will use with atomics. */
+typedef struct {
+ uint8_t values[BUFFER_SIZE];
+} Buffer;
+
+/* Atomic data our threads will be competing over accessing. */
+static atomic_flag flag_atomic = ATOMIC_FLAG_INIT;
+static atomic_bool bool_atomic = false;
+static atomic_int int_atomic = INT_MAX;
+static _Atomic uint64_t longlong_atomic = 0;
+static _Atomic(uint8_t) byte_atomic = 0;
+static atomic_short short_atomic = 0;
+static atomic_ptrdiff_t ptrdiff_atomic = 0;
+static _Atomic(Buffer) buffer_atomic = { {0} };
+
+/* Utility function to do an "atomic" fetch + add operation on our
+ massive buffer. */
+static void atomic_add_buffer(unsigned tid, int delta) {
+ /* Preload the initial value of the buffer. */
+ Buffer desired, expected = atomic_load(&buffer_atomic);
+
+ /* Attempt to update the value of our buffer to the "desired"
+ value. If another thread has preempted our "atomic" operation
+ and has modified the value first, atomic_compare_exchange()
+ will return false, updating the "expected" value. We increment
+ the new value and try again. */
+ do {
+ printf("Thread[%2u]: Attempting to add to buffer: [%u]\n",
+ tid,
+ expected.values[0]);
+
+ for(unsigned v = 0; v < sizeof(desired.values); ++v)
+ desired.values[v] = expected.values[v] + delta;
+
+ } while(!atomic_compare_exchange_strong(&buffer_atomic,
+ &expected,
+ desired));
+
+ printf("Thread[%2u]: Successfully incremented buffer.\n", tid);
+}
+
+/* Per-thread entry point. */
+static int thread(void *arg) {
+ unsigned tid = (unsigned)arg;
+ int retval = 0;
+
+ /* Do several iterations worth of atomic operations for each thread. */
+ for(unsigned i = 0; i < ITERATION_COUNT; ++i) {
+ /* Create a spin-lock out of "flag_atomic" by repeatedly testing
+ and setting its value, while its previous value was not false
+ (our initial "unlocked" state). */
+ while(atomic_flag_test_and_set(&flag_atomic))
+ printf("Thread[%2u]: Waiting to atomic flag lock.\n", tid);
+
+ printf("Thread[%2u]: Acquired atomic flag lock.\n", tid);
+
+ /* Yield thread execution within our "critical section" to see
+ that other threads aren't able to set "flag_atomic" and enter
+ it as well. */
+ thrd_yield();
+
+ /* Increment the longlong_atomic as a regular counter. */
+ atomic_fetch_add(&longlong_atomic, 1);
+
+ /* Release the ghetto flag_atomic spinlock. */
+ atomic_flag_clear(&flag_atomic);
+ printf("Thread[%2u]: Released atomic flag lock.\n", tid);
+
+ /* Attempt to atomically add a value to our huge buffer structure a
+ few times, to ensure the scheduler isn't able to preempt and break
+ its atomicity. */
+ for(int i = 0; i < BUFFER_UPDATE_COUNT; ++i) {
+ atomic_add_buffer(tid, i);
+ atomic_add_buffer(tid, -i);
+ }
+
+ /* Create a second type of spinlock out of an atomic
+ boolean, doing the same thing as before: attempting
+ to set "bool_atomic" to true if it was previously false
+ to claim the lock. */
+ bool expected = false;
+ while(!atomic_compare_exchange_weak(&bool_atomic,
+ &expected,
+ true)) {
+ printf("Thread[%2u]: Waiting to acquire atomic bool lock.\n", tid);
+ /* This time we won't hog all of the CPU time waiting. */
+ thrd_yield();
+ expected = false;
+ }
+
+ printf("Thread[%2u]: Acquired atomic bool lock.\n", tid);
+
+ /* This time lets give other threads a chance to mess
+ with us by sleeping for 1ms rather than yielding. */
+ static const struct timespec time = { .tv_nsec = 100000000 };
+ thrd_sleep(&time, NULL);
+
+ /* Decrement "short_atomic," treating it as a negative counter. */
+ atomic_fetch_sub(&short_atomic, 1);
+
+ printf("Thread[%2u]: Releasing atomic bool lock.\n", tid);
+
+ /* Do the reverse compare + exchange operation to release the lock, this
+ time expecting it to be previously owned (true) and setting it to
+ false to release. */
+ expected = true;
+ if(!atomic_compare_exchange_strong(&bool_atomic,
+ &expected,
+ false)) {
+ fprintf(stderr,
+ "Thread[%2u]: Unexpected value for atomic bool lock!\n",
+ tid);
+ retval = -1;
+ }
+
+ /* Ensure atomic bitwise operations work on various primitive types. */
+ printf("Thread[%2u]: Performing bitwise operations.\n", tid);
+
+ atomic_fetch_or(&byte_atomic, tid);
+ atomic_fetch_xor(&ptrdiff_atomic, tid);
+ atomic_fetch_and(&int_atomic, tid);
+ }
+
+ /* Return any errors back to the main thread. */
+ return retval;
+}
+
+/* Main thread entry point. */
+int main(int arg, char* argv[]) {
+ int retval = 0;
+ /* Array containing our spawned threads. */
+ thrd_t threads[THREAD_COUNT - 1];
+
+ /* First lets ensure that our atomics report the proper
+ runtime values for being lock-free. */
+ printf("Checking locking characteristics.\n");
+
+ if(!atomic_is_lock_free(&bool_atomic)) {
+ fprintf(stderr, "Bool atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(!atomic_is_lock_free(&byte_atomic)) {
+ fprintf(stderr, "Byte atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(!atomic_is_lock_free(&short_atomic)) {
+ fprintf(stderr, "Short atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(!atomic_is_lock_free(&int_atomic)) {
+ fprintf(stderr, "Int atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(!atomic_is_lock_free(&longlong_atomic)) {
+ fprintf(stderr, "Long long atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(!atomic_is_lock_free(&ptrdiff_atomic)) {
+ fprintf(stderr, "Ptrdiff atomics are not lock free!\n");
+ retval = -1;
+ }
+
+ if(atomic_is_lock_free(&buffer_atomic)) {
+ fprintf(stderr, "Struct atomics are lock free!\n");
+ retval = -1;
+ }
+
+ printf("Running threads: [%u]\n", THREAD_COUNT);
+
+ /* Create N-1 threads running the "thread()" function to
+ manipulate and fight over various atomic data. */
+ for(unsigned t = 0; t < THREAD_COUNT - 1; ++t) {
+ if(thrd_create(&threads[t], thread,
+ (void *)t + 1) != thrd_success) {
+ fprintf(stderr, "Failed to create thread: [%u]\n", t + 1);
+ retval = -1;
+ }
+ }
+
+ /* Run the same logic for the main thread as the last one (Thread 0). */
+ if(thread((void *)0) == -1)
+ retval = -1;
+
+ /* Await for each thread to complete its tasks and return its
+ satus code. */
+ printf("Joining threads: [%u]\n", THREAD_COUNT);
+
+ for(unsigned t = 0; t < THREAD_COUNT - 1; ++t) {
+ int res;
+ if(thrd_join(threads[t], &res) == thrd_error) {
+ fprintf(stderr, "Failed to join thread: [%u]\n", t + 1);
+ retval = -1;
+ continue;
+ }
+
+ if(res == -1)
+ retval = -1;
+ }
+
+ /* Validate that all of our atomics have their expected final values. */
+ printf("\nValidating results:\n");
+
+ /* Verify atomic_flag state. */
+ if(atomic_flag_test_and_set(&flag_atomic)) {
+ fprintf(stderr, "flag_atomic left in unexpected state: [true]\n");
+ retval = -1;
+ }
+ else {
+ printf("\tFlag atomics work.\n");
+ }
+
+ /* Verify atomic bool state. */
+ bool expected = false;
+ if(!atomic_compare_exchange_weak(&bool_atomic,
+ &expected,
+ true)) {
+ fprintf(stderr, "bool_atomic left in unexpected state: [true]\n");
+ retval = -1;
+ }
+ else {
+ printf("\tBool atomics work.\n");
+ }
+
+ /* Verify atomic byte state. */
+ uint8_t byte_value, byte_expected_value = 0;
+ for(unsigned i = 0; i < THREAD_COUNT; ++i) {
+ byte_expected_value |= i;
+ }
+
+ if((byte_value = atomic_load(&byte_atomic)) != byte_expected_value) {
+ fprintf(stderr,
+ "byte_atomic left in unexpected state: [%u]\n",
+ byte_value);
+ retval = -1;
+ }
+ else {
+ printf("\t8-bit atomics work.\n");
+ }
+
+ /* Verify atomic short state. */
+ short short_value;
+ /* Note that memory order shouldn't do anything for our platform, just testing. */
+ if((short_value = atomic_load(&short_atomic)) !=
+ -(THREAD_COUNT * ITERATION_COUNT)) {
+ fprintf(stderr,
+ "short_atomic left in unexpected state: [%i]\n",
+ short_value);
+ retval = -1;
+ }
+ else {
+ printf("\t16-bit atomics work.\n");
+ }
+
+ /* Verify atomic int state. */
+ int int_value, int_expected_value = INT_MAX;
+ for(int i = 0; i < THREAD_COUNT; ++i) {
+ int_expected_value &= i;
+ }
+
+ if((int_value = atomic_load(&int_atomic)) != int_expected_value) {
+ fprintf(stderr,
+ "int_atomic left in unexpected state: [%d]\n",
+ int_value);
+ retval = -1;
+ }
+ else {
+ printf("\t32-bit atomics work.\n");
+ }
+
+ /* Verify atomic long long state. */
+ uint64_t longlong_value;
+ if((longlong_value = atomic_load(&longlong_atomic)) !=
+ THREAD_COUNT * ITERATION_COUNT) {
+ fprintf(stderr,
+ "longlong_atomic left in unexpected state: [%llu]\n",
+ longlong_value);
+ retval = -1;
+ }
+ else {
+ printf("\t64-bit atomics work.\n");
+ }
+
+ /* Verify atomic ptrdiff_t state. */
+ ptrdiff_t ptrdiff_value, ptrdiff_expected_value = 0;
+ for(unsigned i = 0; i < THREAD_COUNT; ++i)
+ ptrdiff_expected_value ^= i;
+
+ if((ptrdiff_value = atomic_load(&ptrdiff_atomic))
+ != ptrdiff_expected_value)
+ {
+ fprintf(stderr,
+ "ptrdiff_atomic left in unexpected state: [%d]\n",
+ ptrdiff_value);
+ retval = -1;
+ }
+ else {
+ printf("\tptrdiff_t atomics work.\n");
+ }
+
+ /* Verify atomic buffer state. */
+ Buffer buff_value = atomic_load(&buffer_atomic);
+ bool buffer_works = true;
+ for(unsigned v = 0; v < sizeof(buff_value.values); ++v) {
+ if(buff_value.values[v]) {
+ fprintf(stderr,
+ "buffer_atomic[%u] left in unexpected state: [%d]\n",
+ v,
+ buff_value.values[v]);
+ buffer_works = false;
+ retval = -1;
+ }
+ }
+
+ if(buffer_works)
+ printf("\tGeneric atomics work.\n");
+
+ /* Print final test results and return status code. */
+ if(retval == -1) {
+ fprintf(stderr, "\n***** C11 ATOMICS TEST FAILED! *****\n\n");
+ return EXIT_FAILURE;
+ }
+ else {
+ printf("\n***** C11 ATOMICS TEST PASSED! *****\n\n");
+ return EXIT_SUCCESS;
+ }
+}
+
diff --git a/kernel/libc/c11/Makefile b/kernel/libc/c11/Makefile
index 4328d16..460e5bc 100644
--- a/kernel/libc/c11/Makefile
+++ b/kernel/libc/c11/Makefile
@@ -11,6 +11,6 @@ OBJS = call_once.o cnd_broadcast.o cnd_destroy.o cnd_init.o cnd_signal.o \
mtx_timedlock.o mtx_trylock.o mtx_unlock.o thrd_create.o thrd_current.o \
...<truncated>...
hooks/post-receive
--
A pseudo Operating System for the Dreamcast.
|
