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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/thread/x86_64
parent90f09a0dde3b37ebfabc4d3f6e2bb64086b7e804 (diff)
downloadmusl-feee98903cd8119d9a3db62589246a940f44a9f5.tar.gz
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/thread/x86_64')
-rw-r--r--src/thread/x86_64/syscall_cp.s24
1 files changed, 24 insertions, 0 deletions
diff --git a/src/thread/x86_64/syscall_cp.s b/src/thread/x86_64/syscall_cp.s
new file mode 100644
index 00000000..1894ce19
--- /dev/null
+++ b/src/thread/x86_64/syscall_cp.s
@@ -0,0 +1,24 @@
+.text
+.global __syscall_cp_asm
+.type __syscall_cp_asm,%function
+__syscall_cp_asm:
+ lea 1f(%rip),%rax
+ mov %rax,8(%rdi)
+ mov %rsp,(%rdi)
+ mov 16(%rdi),%eax
+ test %eax,%eax
+ jnz 2f
+ mov %rsi,%rax
+ mov %rdx,%rdi
+ mov %rcx,%rsi
+ mov %r8,%rdx
+ mov %r9,%r10
+ mov 8(%rsp),%r8
+ mov 16(%rsp),%r9
+1: syscall
+ ret
+2: xor %edi,%edi
+ mov %rdi,8(%r10)
+ mov %rdi,(%r10)
+ dec %rdi
+ jmp pthread_exit