threads: implement support for unnamed semaphores (#316)

[POSIX semaphores] come in two forms: named and unnamed. Roughly, named
semaphores use files to implement locking across processes; unnamed
semaphores use a shared memory region to implement locking across
threads in the same process. Since WASI currently has no process concept
(and it is relatively unclear how to map the WASI files as shared
memory), only the unnamed semaphores are supported by this changed. This
means that `sem_open`, `sem_close`, and `sem_unlink` will not available
to programs compiled with a threads-enabled `wasi-libc`.

[POSIX semaphores]: https://man7.org/linux/man-pages/man7/sem_overview.7.html

diff --git a/Makefile b/Makefile
index f73371a944a3d4f1462e165d9ed6bdfffa919faf..16da0f88ef455b5df6199ad1d06fc48be11b30f1 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -192,6 +192,7 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
     $(addprefix $(LIBC_TOP_HALF_MUSL_SRC_DIR)/, \
         thread/__wait.c \
         thread/__timedwait.c \
+        thread/pthread_cleanup_push.c \
         thread/pthread_mutex_consistent.c \
         thread/pthread_mutex_destroy.c \
         thread/pthread_mutex_init.c \
@@ -206,6 +207,14 @@ LIBC_TOP_HALF_MUSL_SOURCES += \
         thread/pthread_mutexattr_setpshared.c \
         thread/pthread_mutexattr_setrobust.c \
         thread/pthread_mutexattr_settype.c \
+        thread/pthread_testcancel.c \
+        thread/sem_destroy.c \
+        thread/sem_getvalue.c \
+        thread/sem_init.c \
+        thread/sem_post.c \
+        thread/sem_timedwait.c \
+        thread/sem_trywait.c \
+        thread/sem_wait.c \
         thread/pthread_setcancelstate.c \
     )
 endif

diff --git a/expected/wasm32-wasi/posix/defined-symbols.txt b/expected/wasm32-wasi/posix/defined-symbols.txt
index 5dfd0f6e3e946934a3fe07a36b99e5f5b093139b..fe91e4f17d81ae672d06b800d3b53d75588c13fb 100644 (file)
--- a/expected/wasm32-wasi/posix/defined-symbols.txt
+++ b/expected/wasm32-wasi/posix/defined-symbols.txt
@@ -38,6 +38,8 @@ __ctype_toupper_loc
 __cxa_atexit
 __cxa_finalize
 __des_setkey
+__do_cleanup_pop
+__do_cleanup_push
 __do_des
 __duplocale
 __env_rm_add
@@ -185,6 +187,7 @@ __pthread_mutex_trylock
 __pthread_mutex_trylock_owner
 __pthread_mutex_unlock
 __pthread_setcancelstate
+__pthread_testcancel
 __putenv
 __qsort_r
 __rand48_step
@@ -243,6 +246,7 @@ __sysv_signal
 __tan
 __tandf
 __tanl
+__testcancel
 __timedwait
 __timedwait_cp
 __tm_to_secs
@@ -365,6 +369,8 @@ _environ
 _exit
 _flushlbf
 _initialize
+_pthread_cleanup_pop
+_pthread_cleanup_push
 _start
 a64l
 abort
@@ -939,6 +945,7 @@ pthread_mutexattr_setpshared
 pthread_mutexattr_setrobust
 pthread_mutexattr_settype
 pthread_setcancelstate
+pthread_testcancel
 putc
 putc_unlocked
 putchar
@@ -1007,6 +1014,13 @@ sched_yield
 seed48
 seekdir
 select
+sem_destroy
+sem_getvalue
+sem_init
+sem_post
+sem_timedwait
+sem_trywait
+sem_wait
 send
 setbuf
 setbuffer

diff --git a/expected/wasm32-wasi/posix/predefined-macros.txt b/expected/wasm32-wasi/posix/predefined-macros.txt
index fd928b760a4782c3161a567412c18341190b7f81..ac909209ea7f1dbe2a6bb63c264fdb8e703818ad 100644 (file)
--- a/expected/wasm32-wasi/posix/predefined-macros.txt
+++ b/expected/wasm32-wasi/posix/predefined-macros.txt
@@ -1580,6 +1580,8 @@
 #define SEEK_SET __WASI_WHENCE_SET
 #define SEGSIZE 512
 #define SEM_FAILED ((sem_t *)0)
+#define SEM_NSEMS_MAX 256
+#define SEM_VALUE_MAX 0x7fffffff
 #define SERVFAIL ns_r_servfail
 #define SHORTBITS (sizeof(short) * 8)
 #define SHRT_MAX 0x7fff

diff --git a/libc-top-half/musl/include/limits.h b/libc-top-half/musl/include/limits.h
index a78cb2f7fb0c832e3ca4f35dfdf60f2805f77ef4..2fc0d2a38afadb8300cf511a91ccc09023478e27 100644 (file)
--- a/libc-top-half/musl/include/limits.h
+++ b/libc-top-half/musl/include/limits.h
@@ -70,7 +70,7 @@
 #define PTHREAD_STACK_MIN 2048
 #define PTHREAD_DESTRUCTOR_ITERATIONS 4
 #endif
-#ifdef __wasilibc_unmodified_upstream /* WASI has no semaphores */
+#if defined(__wasilibc_unmodified_upstream) || defined(_REENTRANT)
 #define SEM_VALUE_MAX 0x7fffffff
 #define SEM_NSEMS_MAX 256
 #endif