diff options
| author | Justus Winter <4winter@informatik.uni-hamburg.de> | 2015-08-18 12:07:26 +0200 |
|---|---|---|
| committer | Justus Winter <4winter@informatik.uni-hamburg.de> | 2015-08-20 19:59:30 +0200 |
| commit | 35cab1dc03d4454a523c4611f7c770029c29da19 (patch) | |
| tree | 7dee8f9f9d498e13c4e697a1905be1b9ee7d4169 /kern | |
| parent | c098b6467ff5cfc25dd800d5bb2966f6ba3edff7 (diff) | |
kern: provide a way to steal a lock
During the message transport, the sender acquires a lock that is
released by the sender. By making this explicit, we can provide
stronger guarantees about the locking.
* ipc/ipc_mqueue.c (ipc_mqueue_receive): Steal lock.
* ipc/ipc_object.h (io_lock_steal): New macro.
* ipc/ipc_port.h (ip_lock_steal): Likewise.
* ipc/mach_msg.c (mach_msg_trap): Steal lock in the inlined version of
`ipc_mqueue_receive'.
* kern/lock.c (lock_done): Assert that the current thread holds the lock.
* kern/lock.h (lock_write_steal): New macro.
Diffstat (limited to 'kern')
| -rw-r--r-- | kern/lock.c | 1 | ||||
| -rw-r--r-- | kern/lock.h | 11 |
2 files changed, 12 insertions, 0 deletions
diff --git a/kern/lock.c b/kern/lock.c index 1daf1b4..473e602 100644 --- a/kern/lock.c +++ b/kern/lock.c @@ -340,6 +340,7 @@ void lock_done( else { l->want_write = FALSE; #if MACH_LDEBUG + assert(have_write_lock(l)); l->writer = THREAD_NULL; #endif /* MACH_LDEBUG */ } diff --git a/kern/lock.h b/kern/lock.h index 74cd933..c8af883 100644 --- a/kern/lock.h +++ b/kern/lock.h @@ -211,10 +211,21 @@ extern void lock_clear_recursive(lock_t); #if ! MACH_LDEBUG #define have_read_lock(l) 1 #define have_write_lock(l) 1 +#define lock_write_surrender(l) +#define lock_write_steal(l) #else /* MACH_LDEBUG */ /* XXX: We don't keep track of readers, so this is an approximation. */ #define have_read_lock(l) ((l)->read_count > 0) #define have_write_lock(l) ((l)->writer == current_thread()) +#define THREAD_SURRENDERED ((thread_t) ~0U) +#define lock_write_surrender(l) ({ \ + assert(have_write_lock(l)); \ + (l)->writer = THREAD_SURRENDERED; \ + }) +#define lock_write_steal(l) ({ \ + assert((l)->writer == THREAD_SURRENDERED); \ + (l)->writer = current_thread(); \ + }) #endif /* MACH_LDEBUG */ #define have_lock(l) (have_read_lock(l) || have_write_lock(l)) |