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git://git.musl-libc.org/musl
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feee98903c
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.
26 lines
782 B
C
26 lines
782 B
C
struct __ptcb {
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long __jb[7];
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int __dummy;
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struct __ptcb *__next;
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void *__ptrs[3];
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};
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static inline void __pthread_register_cancel_2(struct __ptcb *__cb)
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{
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__asm__ __volatile__( "call __pthread_register_cancel" : : "a"(__cb) : "ecx", "edx", "memory" );
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}
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static inline void __pthread_unregister_cancel_2(struct __ptcb *__cb)
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{
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__asm__ __volatile__( "call __pthread_unregister_cancel" : : "a"(__cb) : "ecx", "edx", "memory" );
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}
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static inline void __pthread_unwind_next_2(struct __ptcb *__cb)
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{
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__asm__ __volatile__( "call __pthread_unwind_next" : : "a"(__cb) : "ecx", "edx", "memory" );
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}
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#define __pthread_register_cancel __pthread_register_cancel_2
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#define __pthread_unregister_cancel __pthread_unregister_cancel_2
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#define __pthread_unwind_next __pthread_unwind_next_2
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