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authorAlexey Brodkin <Alexey.Brodkin@synopsys.com>2016-07-29 09:17:19 (GMT)
committerWaldemar Brodkorb <wbx@uclibc-ng.org>2016-07-31 10:50:54 (GMT)
commitb2c2bbcc8ccd0d0b281db653d22e568b8871ad46 (patch)
tree24a23d43d39ad86b6d058ae39c6d57f04859a7ad
parent25f4ae1de711b2001b4958d65e77b6dba222e7b5 (diff)
arc: clone: Fix CLONE_THREAD detection
For thread group case (CLONE_THREAD), the cached PID of new process/thread need not be reset. The old logic to decide that was flawed as it would be true only for exact combination of CLONE_THREAD + _VM, but would fail for CLONE_THREAD + _VM + _xyz. More detailed tear-down of current and new code below. Current implementation is: --------------------->8-------------------- ; r12 contains clone flags mov_s r2, CLONE_THREAD_N_VM; r2 contains bit mask and_s r2, r2, r12 ; r2 contains bit mask AND clone flags ; but r12 still contains the same flags brne r2, r12, .Lgo_thread ; here we compare modified mask with ; flags as they were and skip pthread TID/PID ; setup if r2 != r12 which happens all ; the time except clone flags were ; exactly CLONE_THREAD | CLONE_VM --------------------->8-------------------- New implementation is: --------------------->8-------------------- ; r12 contains clone flags mov_s r2, CLONE_THREAD_N_VM; r2 contains bit mask and_s r12, r12, r2 ; r12 contains clone flags AND bit mask ; i.e. we did mask all flags except ; CLONE_THREAD and CLONE_VM breq r2, r12, .Lgo_thread ; here we compare masked flags with ; target mask and if they match we skip ; pthread TID/PID setup --------------------->8-------------------- Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Acked-by: Vineet Gupta <vgupta@synopsys.com>
-rw-r--r--libc/sysdeps/linux/arc/clone.S4
1 files changed, 2 insertions, 2 deletions
diff --git a/libc/sysdeps/linux/arc/clone.S b/libc/sysdeps/linux/arc/clone.S
index dbb3fa7..fc8dfcf 100644
--- a/libc/sysdeps/linux/arc/clone.S
+++ b/libc/sysdeps/linux/arc/clone.S
@@ -69,8 +69,8 @@ ENTRY(clone)
.Lnext_clone_quirk:
#ifdef RESET_PID
mov_s r2, CLONE_THREAD_N_VM
- and_s r2, r2, r12
- brne r2, r12, .Lgo_thread
+ and_s r12, r12, r2
+ breq r2, r12, .Lgo_thread
mov r8, __NR_getpid
ARC_TRAP_INSN ; r0 has PID