P21: Implementation of Hardware Spinlocks and Basic Concurrency#214
Merged
codenet merged 1 commit intocodenet:p21-spinlocksfrom Mar 14, 2026
Merged
P21: Implementation of Hardware Spinlocks and Basic Concurrency#214codenet merged 1 commit intocodenet:p21-spinlocksfrom
codenet merged 1 commit intocodenet:p21-spinlocksfrom
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Mar 14, 2026
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The PR looks very clean. Thanks.
But looks like it is missing locks. Can you carefully check it again?
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Owner
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Actually, let me merge it so other students can fix missing locks etc. |
Author
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Done, I have merged p22-sleeplocks into my branch and manually resolved all the merge conflicts |
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Note: I have targeted the p20-exec branch for this PR because the p21 branch does not yet exist in the upstream repo. Once the p21 branch is created, the base branch of this PR can be changed to p21 for merging.
Overview
This PR implements the P21 requirements by introducing basic concurrency controls. I have added hardware spinlocks and protected all core OS data structures to match the
xv6-publicstandard, preventing single-processor interrupt race conditions.Key Implementations:
spinlock.hand implementedacquire/releaselogic utilizing the existingpushcliandpopcliinterrupt controls.kalloc.c: Protected the physical memory allocator (kmem.lock).proc.c: Protected the process table (ptable.lock) and implementedforkretto properly release the scheduler lock for newly allocated processes.bio.c: Protected the block buffer cache (bcache.lock) across all return paths.file.c: Protected the open file table (ftable.lock).fs.c: Protected the inode cache (icache.lock), ensuring the lock is temporarily released before disk I/O iniputto prevent deadlocks duringitrunc.ide.c: Protected the disk request queue (idelock) while safely keeping the wait loop lock-free.console.c,trap.c,log.c: Secured the console (cons.lock), timer ticks (tickslock), and log headers (log.lockvialog_write).(Note:
fileread,filewrite, andconsolereadare intentionally left lock-free as they rely on Sleep Locks, which are planned for P22).