diff options
| author | Maria Matejka <mq@ucw.cz> | 2023-05-05 09:39:13 +0200 |
|---|---|---|
| committer | Maria Matejka <mq@ucw.cz> | 2023-05-06 10:50:32 +0200 |
| commit | a95141111c89803347c36501185a76fc73a9764a (patch) | |
| tree | a96a54914cf2498d02546ed49f8e2b852680229b /lib | |
| parent | 00f30ac40bda76b289b1dc5c5aa8a5d2e4941985 (diff) | |
Fixed a bug in hot page global storage
The original algorithm was suffering from an ABA race condition:
A: fp = page_stack
B: completely allocates the same page and writes into it some data
A: unsuspecting, loads (invalid) next = fp->next
B: finishes working with the page and returns it back to page_stack
A: compare-exchange page_stack: fp => next succeeds and writes garbage
to page_stack
Fixed this by using an implicit spinlock in hot page allocator.
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/birdlib.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/lib/birdlib.h b/lib/birdlib.h index 9132fb93..2eec5c0f 100644 --- a/lib/birdlib.h +++ b/lib/birdlib.h @@ -183,7 +183,11 @@ void bug(const char *msg, ...) NORET; void debug(const char *msg, ...); /* Printf to debug output */ void debug_safe(const char *msg); /* Printf to debug output, async-safe */ +/* Internal thread ID, useful for logging */ +extern _Atomic uint max_thread_id; extern _Thread_local uint this_thread_id; +#define THIS_THREAD_ID (this_thread_id ?: (this_thread_id = atomic_fetch_add_explicit(&max_thread_id, 1, memory_order_acq_rel))) + /* Debugging */ |