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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | */ |
27 | */ |
| 28 | 28 | ||
| - | 29 | /** |
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| - | 30 | * @file rwlock.c |
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| 29 | /** Reader/Writer locks |
31 | * @brief Reader/Writer locks. |
| 30 | * |
32 | * |
| 31 | * A reader/writer lock can be held by multiple readers at a time. |
33 | * A reader/writer lock can be held by multiple readers at a time. |
| 32 | * Or it can be exclusively held by a sole writer at a time. |
34 | * Or it can be exclusively held by a sole writer at a time. |
| 33 | */ |
35 | * |
| 34 | - | ||
| 35 | /* |
- | |
| 36 | * These locks are not recursive. |
36 | * These locks are not recursive. |
| - | 37 | * Because technique called direct hand-off is used, neither readers |
|
| 37 | * Neither readers nor writers will suffer starvation. |
38 | * nor writers will suffer starvation. |
| 38 | * |
39 | * |
| 39 | * If there is a writer followed by a reader waiting for the rwlock |
40 | * If there is a writer followed by a reader waiting for the rwlock |
| 40 | * and the writer times out, all leading readers are automatically woken up |
41 | * and the writer times out, all leading readers are automatically woken up |
| 41 | * and allowed in. |
42 | * and allowed in. |
| 42 | */ |
43 | */ |
| Line 143... | Line 144... | ||
| 143 | * @param rwl Reader/Writer lock. |
144 | * @param rwl Reader/Writer lock. |
| 144 | * @param usec Timeout in microseconds. |
145 | * @param usec Timeout in microseconds. |
| 145 | * @param trylock Switches between blocking and non-blocking mode. |
146 | * @param trylock Switches between blocking and non-blocking mode. |
| 146 | * |
147 | * |
| 147 | * For exact description of possible combinations of |
148 | * For exact description of possible combinations of |
| 148 | * @usec and @trylock, see comment for waitq_sleep_timeout(). |
149 | * usec and trylock, see comment for waitq_sleep_timeout(). |
| 149 | * |
150 | * |
| 150 | * @return See comment for waitq_sleep_timeout(). |
151 | * @return See comment for waitq_sleep_timeout(). |
| 151 | */ |
152 | */ |
| 152 | int _rwlock_read_lock_timeout(rwlock_t *rwl, __u32 usec, int trylock) |
153 | int _rwlock_read_lock_timeout(rwlock_t *rwl, __u32 usec, int trylock) |
| 153 | { |
154 | { |