From be9caff6b158a762418815ff2cbaf521b6727029 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jan@jantuomi.fi>
Date: Sat, 18 Jan 2025 09:48:55 +0200
Subject: Make lock manager stricter

---
 log_db/src/lock.rs | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

(limited to 'log_db/src/lock.rs')

diff --git a/log_db/src/lock.rs b/log_db/src/lock.rs
index 01961f9..adb2809 100644
--- a/log_db/src/lock.rs
+++ b/log_db/src/lock.rs
@@ -12,7 +12,6 @@ enum LockState {
     NotLocked,
     Shared,
     Exclusive,
-    ManualExclusive,
 }
 
 impl LockManager {
@@ -47,7 +46,13 @@ impl LockManager {
 
     pub fn lock_shared(&mut self) -> DBResult<()> {
         if self.state == LockState::Shared {
-            return Ok(());
+            return Err(DBError::LockRequestError(
+                "Already holding a shared lock".to_owned(),
+            ));
+        } else if self.state == LockState::Exclusive {
+            return Err(DBError::LockRequestError(
+                "Cannot acquire shared lock while holding an exclusive lock".to_owned(),
+            ));
         }
 
         let mut timeout = 5;
@@ -74,8 +79,14 @@ impl LockManager {
     }
 
     pub fn lock_exclusive(&mut self) -> DBResult<()> {
-        if self.state == LockState::Exclusive || self.state == LockState::ManualExclusive {
-            return Ok(());
+        if self.state == LockState::Exclusive {
+            return Err(DBError::LockRequestError(
+                "Already holding an exclusive lock".to_owned(),
+            ));
+        } else if self.state == LockState::Shared {
+            return Err(DBError::LockRequestError(
+                "Cannot acquire exclusive lock while holding a shared lock".to_owned(),
+            ));
         }
 
         // Create a lock on the exclusive lock request file to signal to readers that they should wait
@@ -93,6 +104,12 @@ impl LockManager {
     }
 
     pub fn unlock(&mut self) -> DBResult<()> {
+        if self.state == LockState::NotLocked {
+            return Err(DBError::LockRequestError(
+                "Not holding any locks".to_owned(),
+            ));
+        }
+
         self.lock_file.unlock()?;
         self.state = LockState::NotLocked;
         Ok(())
-- 
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