path: root/arch
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authorRich Felker <>2011-04-17 11:43:03 -0400
committerRich Felker <>2011-04-17 11:43:03 -0400
commitfeee98903cd8119d9a3db62589246a940f44a9f5 (patch)
tree37922ce54f00145d7fc0ac795216fce611e0806a /arch
parent90f09a0dde3b37ebfabc4d3f6e2bb64086b7e804 (diff)
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 'arch')
5 files changed, 12 insertions, 9 deletions
diff --git a/arch/i386/bits/pthread.h b/arch/i386/bits/pthread.h
index 7690ea39..c119dc8a 100644
--- a/arch/i386/bits/pthread.h
+++ b/arch/i386/bits/pthread.h
@@ -7,17 +7,17 @@ struct __ptcb {
static inline void __pthread_register_cancel_2(struct __ptcb *__cb)
- __asm__ __volatile__( "call __pthread_register_cancel" : : "a"(__cb) );
+ __asm__ __volatile__( "call __pthread_register_cancel" : : "a"(__cb) : "ecx", "edx", "memory" );
static inline void __pthread_unregister_cancel_2(struct __ptcb *__cb)
- __asm__ __volatile__( "call __pthread_unregister_cancel" : : "a"(__cb) );
+ __asm__ __volatile__( "call __pthread_unregister_cancel" : : "a"(__cb) : "ecx", "edx", "memory" );
static inline void __pthread_unwind_next_2(struct __ptcb *__cb)
- __asm__ __volatile__( "call __pthread_unwind_next" : : "a"(__cb) );
+ __asm__ __volatile__( "call __pthread_unwind_next" : : "a"(__cb) : "ecx", "edx", "memory" );
#define __pthread_register_cancel __pthread_register_cancel_2
diff --git a/arch/i386/bits/syscall.h b/arch/i386/bits/syscall.h
index 519e2dcd..274f205c 100644
--- a/arch/i386/bits/syscall.h
+++ b/arch/i386/bits/syscall.h
@@ -122,7 +122,9 @@ static inline long __syscall6(long __n, long __a1, long __a2, long __a3, long __
#define __SC_sendmsg 16
#define __SC_recvmsg 17
-#define __socketcall(nm, a, b, c, d, e, f) syscall(SYS_socketcall, __SC_##nm, \
+#define __socketcall(nm,a,b,c,d,e,f) syscall(SYS_socketcall, __SC_##nm, \
+ ((long [6]){ (long)a, (long)b, (long)c, (long)d, (long)e, (long)f }))
+#define __socketcall_cp(nm,a,b,c,d,e,f) syscall_cp(SYS_socketcall, __SC_##nm, \
((long [6]){ (long)a, (long)b, (long)c, (long)d, (long)e, (long)f }))
#define __NR_restart_syscall 0
diff --git a/arch/i386/pthread_arch.h b/arch/i386/pthread_arch.h
index 64d75cbc..b17dc87a 100644
--- a/arch/i386/pthread_arch.h
+++ b/arch/i386/pthread_arch.h
@@ -5,5 +5,5 @@ static inline struct pthread *__pthread_self()
return self;
-#define PC_AT_SYS(c) \
- (*(uint16_t *)(((ucontext_t *)(c))->uc_mcontext.__gregs[14])==0x80cd)
+#define CANCEL_REG_SP 7
+#define CANCEL_REG_IP 14
diff --git a/arch/x86_64/bits/syscall.h b/arch/x86_64/bits/syscall.h
index d18edece..21d4c23a 100644
--- a/arch/x86_64/bits/syscall.h
+++ b/arch/x86_64/bits/syscall.h
@@ -60,7 +60,8 @@ static inline long __syscall6(long __n, long __a1, long __a2, long __a3, long __
return __ret;
-#define __socketcall(nm, a, b, c, d, e, f) syscall(__NR_##nm, a, b, c, d, e, f)
+#define __socketcall(nm,a,b,c,d,e,f) syscall(__NR_##nm, a, b, c, d, e, f)
+#define __socketcall_cp(nm,a,b,c,d,e,f) syscall_cp(__NR_##nm, a, b, c, d, e, f)
#define __NR_read 0
#define __NR_write 1
diff --git a/arch/x86_64/pthread_arch.h b/arch/x86_64/pthread_arch.h
index af7ae86e..c424493a 100644
--- a/arch/x86_64/pthread_arch.h
+++ b/arch/x86_64/pthread_arch.h
@@ -5,5 +5,5 @@ static inline struct pthread *__pthread_self()
return self;
-#define PC_AT_SYS(c) \
- (*(uint16_t *)(((ucontext_t *)(c))->uc_mcontext.__gregs[16])==0x050f)
+#define CANCEL_REG_SP 15
+#define CANCEL_REG_IP 16