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| author | mjg <mjg@FreeBSD.org> | 2017-03-16 06:51:00 +0000 |
|---|---|---|
| committer | mjg <mjg@FreeBSD.org> | 2017-03-16 06:51:00 +0000 |
| commit | d975a1ed7e0a13af274dc760127a8bf4b0da6130 (patch) | |
| tree | 3a0140220b257844885738a3e4ace466d83c38e5 /sys/sys | |
| parent | f690d08c057e8a0ec75f68e6a3b2e1d3d68ec977 (diff) | |
| download | FreeBSD-src-d975a1ed7e0a13af274dc760127a8bf4b0da6130.zip FreeBSD-src-d975a1ed7e0a13af274dc760127a8bf4b0da6130.tar.gz | |
MFC r313392,r313784:
rwlock: implement RW_LOCK_WRITER_RECURSED bit
This moves recursion handling out of the inlined wunlock path and in
particular saves a read and a branch.
==
rwlock: tidy up r313392
While a new bit was added and thread alignment got shifted to accomodate it,
RW_READERS_SHIFT was not modified accordingly and clashed with the new flag.
This was surprisingly harmless. If the lock was taken for writing, other flags
were tested. If the lock was taken for reading, it would correctly work for
readers > 1 and this was the only relevant test performed.
Diffstat (limited to 'sys/sys')
| -rw-r--r-- | sys/sys/rwlock.h | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/sys/sys/rwlock.h b/sys/sys/rwlock.h index d6dd4f0..aa4b0cc 100644 --- a/sys/sys/rwlock.h +++ b/sys/sys/rwlock.h @@ -58,13 +58,14 @@ #define RW_LOCK_READ_WAITERS 0x02 #define RW_LOCK_WRITE_WAITERS 0x04 #define RW_LOCK_WRITE_SPINNER 0x08 +#define RW_LOCK_WRITER_RECURSED 0x10 #define RW_LOCK_FLAGMASK \ (RW_LOCK_READ | RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS | \ - RW_LOCK_WRITE_SPINNER) + RW_LOCK_WRITE_SPINNER | RW_LOCK_WRITER_RECURSED) #define RW_LOCK_WAITERS (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS) #define RW_OWNER(x) ((x) & ~RW_LOCK_FLAGMASK) -#define RW_READERS_SHIFT 4 +#define RW_READERS_SHIFT 5 #define RW_READERS(x) (RW_OWNER((x)) >> RW_READERS_SHIFT) #define RW_READERS_LOCK(x) ((x) << RW_READERS_SHIFT | RW_LOCK_READ) #define RW_ONE_READER (1 << RW_READERS_SHIFT) @@ -111,13 +112,9 @@ #define __rw_wunlock(rw, tid, file, line) do { \ uintptr_t _tid = (uintptr_t)(tid); \ \ - if ((rw)->rw_recurse) \ - (rw)->rw_recurse--; \ - else { \ - if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) ||\ - !_rw_write_unlock((rw), _tid))) \ - _rw_wunlock_hard((rw), _tid, (file), (line)); \ - } \ + if (__predict_false(LOCKSTAT_PROFILE_ENABLED(rw__release) || \ + !_rw_write_unlock((rw), _tid))) \ + _rw_wunlock_hard((rw), _tid, (file), (line)); \ } while (0) /* |
