fix skyzh#8 by checking if scheduler thread is running

Author: skyzh

Makefile

@@ -1,5 +1,5 @@
-TYPE=release
-RELEASE_FLAG=--release
+TYPE=debug
+RELEASE_FLAG=
 K=kernel/src
 U=user/src
 TARGET=riscv64gc-unknown-none-elf

README.md

@@ -94,7 +94,8 @@ multiple boards.
     - [ ] Allocator and stdlib in user-space
     - [ ] (WIP) Implement wait syscall
     - [ ] Simple shell
-    - [ ] **(WIP) Investigate frequent kernel panic ([#8](https://github.com/skyzh/core-os-riscv/issues/8))** (I'm mad about this one. I don't know what triggered kernel panic. The kernel just stop at kernelvec.)
+    - [x] Investigate frequent kernel panic ([#8](https://github.com/skyzh/core-os-riscv/issues/8))
+    - [ ] Reimplement process scheduling system ([#9](https://github.com/skyzh/core-os-riscv/issues/9))
 * Filesystem
     - [x] Fake fs and exec system call
     - [x] Real spinlock instead of nulllock

kernel/src/process/context.rs

@@ -55,6 +55,7 @@ pub fn sched() {
     let ctx = core::mem::replace(&mut c.scheduler_context, Context::zero());
 
     let intena = c.intr_lock.is_enabled_before;
+
     swtch(&mut p.context, ctx);
     c.intr_lock.is_enabled_before = intena;
 }

kernel/src/trap.rs

@@ -102,10 +102,12 @@ extern "C" fn kerneltrap() {
     };
 
     if dev_intr == Some(Timer) {
-        let p = &my_cpu().process;
-        if let Some(p) = p {
-            if p.state == process::ProcessState::RUNNING {
-                yield_cpu();
+        if my_cpu().scheduler_context.regs[0] != 0 {
+            let p = &my_cpu().process;
+            if let Some(p) = p {
+                if p.state == process::ProcessState::RUNNING {
+                    yield_cpu();
+                }
             }
         }
     }