diff options
Diffstat (limited to 'src/libstd')
| -rw-r--r-- | src/libstd/sys/unix/rwlock.rs | 26 |
1 files changed, 24 insertions, 2 deletions
diff --git a/src/libstd/sys/unix/rwlock.rs b/src/libstd/sys/unix/rwlock.rs index b754d3a97cf..7bb9fb68c14 100644 --- a/src/libstd/sys/unix/rwlock.rs +++ b/src/libstd/sys/unix/rwlock.rs @@ -10,6 +10,7 @@ use prelude::v1::*; +use libc; use cell::UnsafeCell; use sys::sync as ffi; @@ -26,7 +27,23 @@ impl RWLock { #[inline] pub unsafe fn read(&self) { let r = ffi::pthread_rwlock_rdlock(self.inner.get()); - debug_assert_eq!(r, 0); + + // According to the pthread_rwlock_rdlock spec, this function **may** + // fail with EDEADLK if a deadlock is detected. On the other hand + // pthread mutexes will *never* return EDEADLK if they are initialized + // as the "fast" kind (which ours always are). As a result, a deadlock + // situation may actually return from the call to pthread_rwlock_rdlock + // instead of blocking forever (as mutexes and Windows rwlocks do). Note + // that not all unix implementations, however, will return EDEADLK for + // their rwlocks. + // + // We roughly maintain the deadlocking behavior by panicking to ensure + // that this lock acquisition does not succeed. + if r == libc::EDEADLK { + panic!("rwlock read lock would result in deadlock"); + } else { + debug_assert_eq!(r, 0); + } } #[inline] pub unsafe fn try_read(&self) -> bool { @@ -35,7 +52,12 @@ impl RWLock { #[inline] pub unsafe fn write(&self) { let r = ffi::pthread_rwlock_wrlock(self.inner.get()); - debug_assert_eq!(r, 0); + // see comments above for why we check for EDEADLK + if r == libc::EDEADLK { + panic!("rwlock write lock would result in deadlock"); + } else { + debug_assert_eq!(r, 0); + } } #[inline] pub unsafe fn try_write(&self) -> bool { |