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The first issue fixed in this patch is that pending rwlock write locks could lock out new readers; this could cause a deadlock if a read lock was held on cpu 1, a write lock was then attempted on cpu 2 and was pending, and cpu 1 was interrupted and attempted to re-acquire a read lock. The write lock code was modified to not lock out new readers. The second issue fixed is that there was a narrow race window where a tns instruction had been issued (setting the lock value to "1") and the store instruction to reset the lock value correctly had not yet been issued. In this case, if an interrupt occurred and the same cpu then tried to manipulate the lock, it would find the lock value set to "1" and spin forever, assuming some other cpu was partway through updating it. The fix is to enforce an interrupt critical section around the tns/store pair. In addition, this change now arranges to always validate that after a readlock we have not wrapped around the count of readers, which is only eight bits. Since these changes make the rwlock "fast path" code heavier weight, I decided to move all the rwlock code all out of line, leaving only the conventional spinlock code with fastpath inlines. Since the read_lock and read_trylock implementations ended up very similar, I just expressed read_lock in terms of read_trylock. As part of this change I also eliminate support for the now-obsolete tns_atomic mode. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> |
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| .. | ||
| atomic_32.c | ||
| atomic_asm_32.S | ||
| cacheflush.c | ||
| checksum.c | ||
| cpumask.c | ||
| delay.c | ||
| exports.c | ||
| Makefile | ||
| memchr_32.c | ||
| memcpy_32.S | ||
| memcpy_tile64.c | ||
| memmove.c | ||
| memset_32.c | ||
| spinlock_32.c | ||
| spinlock_common.h | ||
| strchr_32.c | ||
| strlen_32.c | ||
| uaccess.c | ||
| usercopy_32.S | ||