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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/ipc
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/ipc')
-rw-r--r--src/ipc/msgrcv.c8
-rw-r--r--src/ipc/msgsnd.c8
2 files changed, 4 insertions, 12 deletions
diff --git a/src/ipc/msgrcv.c b/src/ipc/msgrcv.c
index 13c282ee..ed4a448a 100644
--- a/src/ipc/msgrcv.c
+++ b/src/ipc/msgrcv.c
@@ -5,13 +5,9 @@
ssize_t msgrcv(int q, void *m, size_t len, long type, int flag)
{
- ssize_t r;
- CANCELPT_BEGIN;
#ifdef SYS_msgrcv
- r = syscall(SYS_msgrcv, q, m, len, type, flag);
+ return syscall_cp(SYS_msgrcv, q, m, len, type, flag);
#else
- r = syscall(SYS_ipc, IPCOP_msgrcv, q, len, flag, ((long[]){ (long)m, type }));
+ return syscall_cp(SYS_ipc, IPCOP_msgrcv, q, len, flag, ((long[]){ (long)m, type }));
#endif
- CANCELPT_END;
- return r;
}
diff --git a/src/ipc/msgsnd.c b/src/ipc/msgsnd.c
index 1e0b2fa5..23f4a4cb 100644
--- a/src/ipc/msgsnd.c
+++ b/src/ipc/msgsnd.c
@@ -5,13 +5,9 @@
int msgsnd(int q, const void *m, size_t len, int flag)
{
- ssize_t r;
- CANCELPT_BEGIN;
#ifdef SYS_msgsnd
- r = syscall(SYS_msgsnd, q, m, len, flag);
+ return syscall_cp(SYS_msgsnd, q, m, len, flag);
#else
- r = syscall(SYS_ipc, IPCOP_msgsnd, q, len, flag, m);
+ return syscall_cp(SYS_ipc, IPCOP_msgsnd, q, len, flag, m);
#endif
- CANCELPT_END;
- return r;
}