Hi,
When copying a thread, access to the FPU is disabled by clearing
the ST0_CU1 bit in the new thread saved CP0_STATUS register. However, the
corresponding TIF_USEDFPU flag is not cleared at it should to indicate the
FPU has not yet been used by the new process.
This patch also clears user_tid in mips64 code, and moves it away
from the FPU comment in the mips code.
Vivien.
Index: arch/mips64/kernel/process.c
===================================================================
RCS file: /home/cvs/linux/arch/mips64/kernel/process.c,v
retrieving revision 1.36
diff -u -r1.36 process.c
--- arch/mips64/kernel/process.c 9 Jan 2003 19:16:50 -0000 1.36
+++ arch/mips64/kernel/process.c 4 Feb 2003 22:47:00 -0000
@@ -114,6 +114,8 @@
p->thread.reg29 = (unsigned long) childregs;
p->thread.reg31 = (unsigned long) ret_from_fork;
+ p->user_tid = NULL;
+
/*
* New tasks loose permission to use the fpu. This accelerates context
* switching for most programs since they don't use the fpu.
@@ -121,6 +123,7 @@
p->thread.cp0_status = read_c0_status() &
~(ST0_CU3|ST0_CU2|ST0_CU1|ST0_KSU);
childregs->cp0_status &= ~(ST0_CU3|ST0_CU2|ST0_CU1);
+ clear_ti_thread_flag(ti, TIF_USEDFPU);
return 0;
}
Index: arch/mips/kernel/process.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/process.c,v
retrieving revision 1.50
diff -u -r1.50 process.c
--- arch/mips/kernel/process.c 9 Jan 2003 19:16:50 -0000 1.50
+++ arch/mips/kernel/process.c 4 Feb 2003 22:47:04 -0000
@@ -117,6 +117,8 @@
p->thread.reg29 = (unsigned long) childregs;
p->thread.reg31 = (unsigned long) ret_from_fork;
+ p->user_tid = NULL;
+
/*
* New tasks loose permission to use the fpu. This accelerates context
* switching for most programs since they don't use the fpu.
@@ -124,7 +126,7 @@
p->thread.cp0_status = read_c0_status() &
~(ST0_CU2|ST0_CU1|KU_MASK);
childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
- p->user_tid = NULL;
+ clear_ti_thread_flag(ti, TIF_USEDFPU);
return 0;
}
