diff options
| -rw-r--r-- | sys/man/2/semacquire | 35 | ||||
| -rw-r--r-- | sys/src/9/port/syscallfmt.c | 5 |
2 files changed, 30 insertions, 10 deletions
diff --git a/sys/man/2/semacquire b/sys/man/2/semacquire index 386734800..0eb0fc97b 100644 --- a/sys/man/2/semacquire +++ b/sys/man/2/semacquire @@ -1,6 +1,6 @@ .TH SEMACQUIRE 2 .SH NAME -semacquire, semrelease \- user level semaphores +semacquire, tsemacquire, semrelease - user level semaphores .SH SYNOPSIS .B #include <u.h> .br @@ -10,10 +10,14 @@ semacquire, semrelease \- user level semaphores int semacquire(long *addr, int block); .PP .B +int tsemacquire(long *addr, ulong ms); +.PP +.B long semrelease(long *addr, long count); .SH DESCRIPTION -.I Semacquire -and +.IR Semacquire , +.IR tsemacquire , +and .I semrelease facilitate scheduling between processes sharing memory. Processes arrange to share memory by using @@ -22,7 +26,7 @@ with the .B RFMEM flag (see -.IR fork (2)), +.IR fork (2)), .IR segattach (2), or .IR thread (2). @@ -32,21 +36,30 @@ The semaphore's value is the integer pointed at by .I Semacquire atomically waits until the semaphore has a positive value and then decrements that value. -It returns 1 if the semaphore was acquired and \-1 on error -(e.g., if it was interrupted). If .I block is zero and the semaphore is not immediately available, .I semacquire returns 0 instead of waiting. +.I Tsemacquire +only waits +.I ms +milliseconds for the semaphore to attain a positive value +and, if available in that time, decrements that value. +It returns 0 otherwise. +Both functions return 1 if the semaphore was acquired +and -1 on error +(e.g., if they were interrupted). .I Semrelease -adds +adds .I count to the semaphore's value and returns the new value. .PP .I Semacquire +(and analogously for +.IR tsemacquire ) and .I semrelease can be thought of as efficient, correct replacements for: @@ -74,7 +87,8 @@ semrelease(long *addr, int count) .PP Like .IR rendezvous (2), -.I semacquire +.IR semacquire , +.IR tsemacquire , and .I semrelease are not typically used directly. @@ -86,8 +100,9 @@ locks, rendezvous points, and channels and .IR thread (2)). Also like -.I rendezvous , -.I semacquire +.IR rendezvous , +.IR semacquire , +.IR tsemacquire , and .I semrelease cannot be used to coordinate between threads diff --git a/sys/src/9/port/syscallfmt.c b/sys/src/9/port/syscallfmt.c index c04cc5cf8..fdd2e0519 100644 --- a/sys/src/9/port/syscallfmt.c +++ b/sys/src/9/port/syscallfmt.c @@ -231,6 +231,11 @@ syscallfmt(int syscallno, ulong pc, va_list list) i[0] = va_arg(list, int); fmtprint(&fmt, "%#p %d", v, i[0]); break; + case TSEMACQUIRE: + v = va_arg(list, int*); + l = va_arg(list, ulong); + fmtprint(&fmt, "%#p %ld", v, l); + break; case SEEK: v = va_arg(list, vlong*); i[0] = va_arg(list, int); |