[cadcdev-svn-commits] [SCM] branch master updated. v2.0.0-1332-gf7a14e26

[falcovorbis <fal...@us...>]

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- Log -----------------------------------------------------------------
commit f7a14e260dc6dfa55eec1f417b2c661101732773
Author: Paul Cercueil <pa...@cr...>
Date:   Sun Apr 21 10:03:27 2024 +0200

    maple: Fix race between IRQ and threads (#517)
    
    The IRQ handler and threads would read-modify-write the state->queue_len
    field as if races didn't exist.
    
    Address this issue by using atomics instead.
    
    Note that the code in the IRQ handler is using atomic routines as well
    just to be future-proof, as it may very well be called from a threaded
    interrupt handler in the future.
    
    This has the added benefit that it also tells GCC that the 'queue_len'
    may be updated outside the visible scope, and therefore its value may
    change at any moment. This fixes the code not working properly when
    building with LTO.
    
    Signed-off-by: Paul Cercueil <pa...@cr...>

-----------------------------------------------------------------------

Summary of changes:
 .gitignore                                        | 2 ++
 kernel/arch/dreamcast/hardware/maple/keyboard.c   | 8 ++++----
 kernel/arch/dreamcast/include/dc/maple/keyboard.h | 4 +++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/.gitignore b/.gitignore
index bfc7f1f1..9d351605 100644
--- a/.gitignore
+++ b/.gitignore
@@ -36,6 +36,8 @@ examples/dreamcast/kgl/basic/vq/fruit.vq
 examples/dreamcast/conio/adventure/data.c
 examples/dreamcast/conio/adventure/datagen
 examples/dreamcast/png/romdisk_boot.img
+examples/dreamcast/pvr/bumpmap/romdisk/bricks.kmg
+examples/dreamcast/pvr/bumpmap/romdisk/bumpmap.raw
 examples/dreamcast/pvr/modifier_volume_tex/romdisk/fruit.kmg
 examples/dreamcast/pvr/texture_render/texture_render.bin
 utils/dc-chain/logs
diff --git a/kernel/arch/dreamcast/hardware/maple/keyboard.c b/kernel/arch/dreamcast/hardware/maple/keyboard.c
index cc5dbe4f..9137ecc8 100644
--- a/kernel/arch/dreamcast/hardware/maple/keyboard.c
+++ b/kernel/arch/dreamcast/hardware/maple/keyboard.c
@@ -410,10 +410,10 @@ static int kbd_enqueue(kbd_state_t *state, uint8 keycode, int mods) {
         return 0;
 
     /* Queue the key up on the device-specific queue. */
-    if(state->queue_len < KBD_QUEUE_SIZE) {
+    if(atomic_load(&state->queue_len) < KBD_QUEUE_SIZE) {
         state->key_queue[state->queue_head] = keycode | (mods << 8);
         state->queue_head = (state->queue_head + 1) & (KBD_QUEUE_SIZE - 1);
-        ++state->queue_len;
+        atomic_fetch_add(&state->queue_len, 1);
     }
 
     /* If queueing is turned off, don't bother with the global queue. */
@@ -463,12 +463,12 @@ int kbd_queue_pop(maple_device_t *dev, int xlat) {
     uint32 rv, mods;
     uint8 ascii;
 
-    if(!state->queue_len)
+    if(!atomic_load(&state->queue_len))
         return -1;
 
     rv = state->key_queue[state->queue_tail];
     state->queue_tail = (state->queue_tail + 1) & (KBD_QUEUE_SIZE - 1);
-    --state->queue_len;
+    atomic_fetch_sub(&state->queue_len, 1);
 
     if(!xlat)
         return (int)rv;
diff --git a/kernel/arch/dreamcast/include/dc/maple/keyboard.h b/kernel/arch/dreamcast/include/dc/maple/keyboard.h
index 51be9173..56d1567e 100644
--- a/kernel/arch/dreamcast/include/dc/maple/keyboard.h
+++ b/kernel/arch/dreamcast/include/dc/maple/keyboard.h
@@ -28,6 +28,8 @@ __BEGIN_DECLS
 #include <arch/types.h>
 #include <dc/maple.h>
 
+#include <stdatomic.h>
+
 /** \defgroup kbd   Keyboard
     \brief          Driver for the Dreamcast's Keyboard Input Device
     \ingroup        peripherals
@@ -297,7 +299,7 @@ typedef struct kbd_state {
     uint32 key_queue[KBD_QUEUE_SIZE];
     int queue_tail;                     /**< \brief Key queue tail. */
     int queue_head;                     /**< \brief Key queue head. */
-    int queue_len;                      /**< \brief Current length of queue. */
+    atomic_int queue_len;               /**< \brief Current length of queue. */
 
     uint8 kbd_repeat_key;           /**< \brief Key that is repeating. */
     uint64 kbd_repeat_timer;        /**< \brief Time that the next repeat will trigger. */


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A pseudo Operating System for the Dreamcast.