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ke/sched: fix lock inversion in scheduler

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Taking next's lock can be a lock inversion with the turnstile code.
Use a switching field instead and spin on that.
This commit is contained in:
Loïc Grégoire
2026-07-19 20:40:50 -04:00
parent ea33fcab30
commit 878be31c7a
4 changed files with 24 additions and 9 deletions
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src/kern/amd64/impl.zig
+2 -2
View File
@@ -25,7 +25,7 @@ const ThreadFrame = extern struct {
extern fn asm_thread_entry() void;
extern fn do_context_switch(old: *ThreadContext, new: *ThreadContext, lock: *u8) callconv(.c) void;
extern fn do_context_switch(old: *ThreadContext, new: *ThreadContext, lock: *u8, switching: *bool) callconv(.c) void;
pub const ThreadContext = extern struct {
rsp: u64 align(1),
@@ -60,7 +60,7 @@ pub const ThreadContext = extern struct {
pub fn switch_to(self: *ThreadContext, new: *ThreadContext) callconv(.c) void {
const thread: *ke.Thread = @alignCast(@fieldParentPtr("context", self));
do_context_switch(self, new, &thread.lock.inner.locked.raw);
do_context_switch(self, new, &thread.lock.inner.locked.raw, &thread.switching.raw);
}
};
src/kern/amd64/locore.s
+6 -2
View File
@@ -149,9 +149,13 @@ do_context_switch:
/* Load new stack pointer. */
mov (%rsi), %rsp
/* Set switching to false. */
xorl %eax, %eax
xchgb %al, (%rcx)
/* Unlock passed lock. */
xorl %ecx, %ecx
xchgb %cl, (%rdx)
xorl %eax, %eax
xchgb %al, (%rdx)
/* Restore callee-saved registers. */
pop %rbp