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authorRich Felker <dalias@aerifal.cx>2011-04-17 11:43:03 -0400
committerRich Felker <dalias@aerifal.cx>2011-04-17 11:43:03 -0400
commitfeee98903cd8119d9a3db62589246a940f44a9f5 (patch)
tree37922ce54f00145d7fc0ac795216fce611e0806a /src/internal
parent90f09a0dde3b37ebfabc4d3f6e2bb64086b7e804 (diff)
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overhaul pthread cancellation
this patch improves the correctness, simplicity, and size of
cancellation-related code. modulo any small errors, it should now be
completely conformant, safe, and resource-leak free.

the notion of entering and exiting cancellation-point context has been
completely eliminated and replaced with alternative syscall assembly
code for cancellable syscalls. the assembly is responsible for setting
up execution context information (stack pointer and address of the
syscall instruction) which the cancellation signal handler can use to
determine whether the interrupted code was in a cancellable state.

these changes eliminate race conditions in the previous generation of
cancellation handling code (whereby a cancellation request received
just prior to the syscall would not be processed, leaving the syscall
to block, potentially indefinitely), and remedy an issue where
non-cancellable syscalls made from signal handlers became cancellable
if the signal handler interrupted a cancellation point.

x86_64 asm is untested and may need a second try to get it right.
Diffstat (limited to 'src/internal')
-rw-r--r--src/internal/libc.h8
-rw-r--r--src/internal/pthread_impl.h4
-rw-r--r--src/internal/syscall.h14
3 files changed, 18 insertions, 8 deletions
diff --git a/src/internal/libc.h b/src/internal/libc.h
index c0039e77..3f1e55e5 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -6,7 +6,7 @@
 
 struct __libc {
 	int *(*errno_location)(void);
-	void (*cancelpt)(int);
+	void (*testcancel)(void);
 	void (*lock)(volatile int *);
 	void (*lockfile)(FILE *);
 	void (*fork_handler)(int);
@@ -40,12 +40,6 @@ void __lock(volatile int *);
 void __lockfile(FILE *);
 #define LOCK(x) (libc.threads_minus_1 ? (__lock(x),1) : ((void)(x),1))
 #define UNLOCK(x) (*(x)=0)
-#define CANCELPT(x) (libc.cancelpt ? libc.cancelpt((x)),0 : (void)(x),0)
-#define CANCELPT_BEGIN CANCELPT(1)
-#define CANCELPT_TRY CANCELPT(0)
-#define CANCELPT_END CANCELPT(-1)
-#define CANCELPT_INHIBIT CANCELPT(2)
-#define CANCELPT_RESUME CANCELPT(-2)
 
 int __rsyscall(int, long, long, long, long, long, long);
 
diff --git a/src/internal/pthread_impl.h b/src/internal/pthread_impl.h
index a6d90e9b..304bf98d 100644
--- a/src/internal/pthread_impl.h
+++ b/src/internal/pthread_impl.h
@@ -24,7 +24,8 @@ struct pthread {
 	unsigned long tlsdesc[4];
 	pid_t tid, pid;
 	int tsd_used, errno_val, *errno_ptr;
-	volatile int canceldisable, cancelasync, cancelpoint, cancel;
+	volatile uintptr_t cp_sp, cp_ip;
+	volatile int cancel, canceldisable, cancelasync;
 	unsigned char *map_base;
 	size_t map_size;
 	void *start_arg;
@@ -85,6 +86,7 @@ void __lock(volatile int *);
 void __unmapself(void *, size_t);
 
 int __timedwait(volatile int *, int, clockid_t, const struct timespec *, int);
+int __timedwait_cp(volatile int *, int, clockid_t, const struct timespec *, int);
 void __wait(volatile int *, volatile int *, int, int);
 void __wake(volatile int *, int, int);
 
diff --git a/src/internal/syscall.h b/src/internal/syscall.h
index 39efc42d..0c71eca6 100644
--- a/src/internal/syscall.h
+++ b/src/internal/syscall.h
@@ -6,5 +6,19 @@
 #include <sys/syscall.h>
 
 #define socketcall __socketcall
+#define socketcall_cp __socketcall_cp
+
+#define __syscall_cp0(n) __syscall_cp(n,0,0,0,0,0,0)
+#define __syscall_cp1(n,a) __syscall_cp(n,(long)(a),0,0,0,0,0)
+#define __syscall_cp2(n,a,b) __syscall_cp(n,(long)(a),(long)(b),0,0,0,0)
+#define __syscall_cp3(n,a,b,c) __syscall_cp(n,(long)(a),(long)(b),(long)(c),0,0,0)
+#define __syscall_cp4(n,a,b,c,d) __syscall_cp(n,(long)(a),(long)(b),(long)(c),(long)(d),0,0)
+#define __syscall_cp5(n,a,b,c,d,e) __syscall_cp(n,(long)(a),(long)(b),(long)(c),(long)(d),(long)(e),0)
+#define __syscall_cp6(n,a,b,c,d,e,f) __syscall_cp(n,(long)(a),(long)(b),(long)(c),(long)(d),(long)(e),(long)(f))
+
+long (__syscall_cp)(long, long, long, long, long, long, long);
+
+#define __syscall_cp(...) __SYSCALL_DISP(__syscall_cp,__VA_ARGS__)
+#define syscall_cp(...) __syscall_ret(__syscall_cp(__VA_ARGS__))
 
 #endif