soundness and cost

Cargo.toml

@@ -46,6 +46,10 @@ trybuild = "1"
 codegen-units = 1
 lto = true
 
+[features]
+inline-asm = ["cortex-m/inline-asm"]
+linker-plugin-lto = ["cortex-m/linker-plugin-lto"]
+
 [workspace]
 members = [
   "macros",

examples/lock_cost.rs

@@ -0,0 +1,79 @@
+//! examples/lock_cost.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use panic_semihosting as _;
+
+#[rtic::app(device = lm3s6965)]
+mod app {
+    #[shared]
+    struct Shared {
+        shared: u32,
+    }
+
+    #[local]
+    struct Local {}
+
+    #[init]
+    fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
+        (Shared { shared: 0 }, Local {}, init::Monotonics())
+    }
+
+    #[idle(shared = [shared])]
+    #[inline(never)]
+    fn idle(mut cx: idle::Context) -> ! {
+        cx.shared.shared.lock(|shared| *shared += 1);
+
+        loop {
+            cortex_m::asm::nop();
+        }
+    }
+
+    #[task(binds = UART0, shared = [shared])]
+    fn uart0(mut cx: uart0::Context) {
+        cx.shared.shared.lock(|shared| *shared += 1);
+    }
+}
+
+// cargo objdump --example lock_cost --target thumbv7m-none-eabi --release --features inline-asm -- --disassemble > lock_cost.objdump
+
+// 0000016c <lock_cost::app::idle::he8e6b27e7333515d>:
+//      16c: 80 b5        	push	{r7, lr}
+//      16e: 6f 46        	mov	r7, sp
+//      170: 01 78        	ldrb	r1, [r0]
+//      172: 39 b1        	cbz	r1, 0x184 <lock_cost::app::idle::he8e6b27e7333515d+0x18> @ imm = #14
+//      174: 40 f2 00 00  	movw	r0, #0
+//      178: c2 f2 00 00  	movt	r0, #8192
+//      17c: 01 68        	ldr	r1, [r0]
+//      17e: 01 31        	adds	r1, #1
+//      180: 01 60        	str	r1, [r0]
+//      182: 0f e0        	b	0x1a4 <lock_cost::app::idle::he8e6b27e7333515d+0x38> @ imm = #30
+//      184: 01 21        	movs	r1, #1
+//      186: 01 70        	strb	r1, [r0]
+//      188: e0 21        	movs	r1, #224
+//      18a: 81 f3 11 88  	msr	basepri, r1
+//      18e: 40 f2 00 01  	movw	r1, #0
+//      192: c2 f2 00 01  	movt	r1, #8192
+//      196: 0a 68        	ldr	r2, [r1]
+//      198: 01 32        	adds	r2, #1
+//      19a: 0a 60        	str	r2, [r1]
+//      19c: 00 21        	movs	r1, #0
+//      19e: 81 f3 11 88  	msr	basepri, r1
+//      1a2: 01 70        	strb	r1, [r0]
+//      1a4: 00 bf        	nop
+//      1a6: fd e7        	b	0x1a4 <lock_cost::app::idle::he8e6b27e7333515d+0x38> @ imm = #-6
+
+// 000001a8 <UART0>:
+//      1a8: 80 b5        	push	{r7, lr}
+//      1aa: 6f 46        	mov	r7, sp
+//      1ac: 40 f2 00 00  	movw	r0, #0
+//      1b0: c2 f2 00 00  	movt	r0, #8192
+//      1b4: 01 68        	ldr	r1, [r0]
+//      1b6: 01 31        	adds	r1, #1
+//      1b8: 01 60        	str	r1, [r0]
+//      1ba: 00 20        	movs	r0, #0
+//      1bc: 80 f3 11 88  	msr	basepri, r0
+//      1c0: 80 bd        	pop	{r7, pc}

examples/lockall_cost.rs

@@ -0,0 +1,81 @@
+//! examples/lockall_cost.rs
+
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use panic_semihosting as _;
+
+#[rtic::app(device = lm3s6965)]
+mod app {
+    #[shared]
+    struct Shared {
+        shared: u32,
+    }
+
+    #[local]
+    struct Local {}
+
+    #[init]
+    fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
+        (Shared { shared: 0 }, Local {}, init::Monotonics())
+    }
+
+    #[idle(shared = [shared])]
+    #[inline(never)]
+    fn idle(mut cx: idle::Context) -> ! {
+        cx.shared.lock(|x| *x.shared += 1);
+
+        loop {
+            cortex_m::asm::nop();
+        }
+    }
+
+    #[task(binds = UART0, shared = [shared])]
+    fn uart0(mut cx: uart0::Context) {
+        cx.shared.lock(|x| *x.shared += 1);
+    }
+}
+
+// cargo objdump --example lockall_cost --target thumbv7m-none-eabi --release --features inline-asm -- --disassemble > lockall_cost.ojbdump
+//
+// The priority cell not optimized out?
+// 0000016c <lockall_cost::app::idle::he14f20fbca3d3928>:
+//      16c: 80 b5        	push	{r7, lr}
+//      16e: 6f 46        	mov	r7, sp
+//      170: 01 78        	ldrb	r1, [r0]
+//      172: 39 b1        	cbz	r1, 0x184 <lockall_cost::app::idle::he14f20fbca3d3928+0x18> @ imm = #14
+//      174: 40 f2 00 00  	movw	r0, #0
+//      178: c2 f2 00 00  	movt	r0, #8192
+//      17c: 01 68        	ldr	r1, [r0]
+//      17e: 01 31        	adds	r1, #1
+//      180: 01 60        	str	r1, [r0]
+//      182: 0f e0        	b	0x1a4 <lockall_cost::app::idle::he14f20fbca3d3928+0x38> @ imm = #30
+//      184: 01 21        	movs	r1, #1
+//      186: 01 70        	strb	r1, [r0]
+//      188: e0 21        	movs	r1, #224
+//      18a: 81 f3 11 88  	msr	basepri, r1
+//      18e: 40 f2 00 01  	movw	r1, #0
+//      192: c2 f2 00 01  	movt	r1, #8192
+//      196: 0a 68        	ldr	r2, [r1]
+//      198: 01 32        	adds	r2, #1
+//      19a: 0a 60        	str	r2, [r1]
+//      19c: 00 21        	movs	r1, #0
+//      19e: 81 f3 11 88  	msr	basepri, r1
+//      1a2: 01 70        	strb	r1, [r0]
+//      1a4: 00 bf        	nop
+//      1a6: fd e7        	b	0x1a4 <lockall_cost::app::idle::he14f20fbca3d3928+0x38> @ imm = #-6
+
+// The lock at highest prio is zero cost
+// 000001a8 <UART0>:
+//      1a8: 80 b5        	push	{r7, lr}
+//      1aa: 6f 46        	mov	r7, sp
+//      1ac: 40 f2 00 00  	movw	r0, #0
+//      1b0: c2 f2 00 00  	movt	r0, #8192
+//      1b4: 01 68        	ldr	r1, [r0]
+//      1b6: 01 31        	adds	r1, #1
+//      1b8: 01 60        	str	r1, [r0]
+//      1ba: 00 20        	movs	r0, #0
+//      1bc: 80 f3 11 88  	msr	basepri, r0
+//      1c0: 80 bd        	pop	{r7, pc}

examples/lockall_soundness3.rs

@@ -0,0 +1,40 @@
+//! examples/lockall_soundness3.rs
+
+#![deny(unsafe_code)]
+// #![deny(warnings)]
+#![no_main]
+#![no_std]
+
+use panic_semihosting as _;
+
+#[rtic::app(device = lm3s6965, dispatchers = [GPIOA])]
+mod app {
+    use cortex_m_semihosting::{debug, hprintln};
+
+    #[shared]
+    struct Shared {
+        a: u32,
+        b: i64,
+    }
+
+    #[local]
+    struct Local {}
+
+    #[init]
+    fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
+        foo::spawn().unwrap();
+
+        (Shared { a: 1, b: 2 }, Local {}, init::Monotonics())
+    }
+
+    // when omitted priority is assumed to be `1`
+    #[task(shared = [a, b])]
+    fn foo(mut c: foo::Context) {
+        // let s = c.shared.lock(|s| s); // lifetime error
+        // hprintln!("a {}", s.a).ok();
+
+        // let a = c.shared.lock(|foo::Shared { a, b: _ }| a); // lifetime error
+        // hprintln!("a {}", a).ok();
+        debug::exit(debug::EXIT_SUCCESS); // Exit QEMU simulator
+    }
+}