path: root/arch/ia64/kernel/ptrace.c
diff options
authorPeter Chubb <peterc@gelato.unsw.edu.au>2005-06-08 15:50:20 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-08 16:21:14 -0700
commit05062d96a23ec0959ee5ea969f40813170c73c0e (patch)
tree9aa09b58ff455cc43b81cae10d3c4dac9fe9f462 /arch/ia64/kernel/ptrace.c
parent[PATCH] ppc64 kprobes: remove spurious MSR_SE masking (diff)
[PATCH] ia64: fix floating-point preemption problem
There've been reports of problems with CONFIG_PREEMPT=y and the high floating point partition. This is caused by the possibility of preemption and rescheduling on a different processor while saving or restioirng the high partition. The only places where the FPU state is touched are in ptrace, in switch_to(), and where handling a floating-point exception. In switch_to() preemption is off. So it's only in trap.c and ptrace.c that we need to prevent preemption. Here is a patch that adds commentary to make the conditions clear, and adds appropriate preempt_{en,dis}able() calls to make it so. In trap.c I use preempt_enable_no_resched(), as we're about to return to user space where the preemption flag will be checked anyway. Signed-off-by: Peter Chubb <peterc@gelato.unsw.edu.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/ia64/kernel/ptrace.c')
1 files changed, 6 insertions, 0 deletions
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 08c8a5eb25ab..575a8f657b31 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -635,11 +635,17 @@ ia64_flush_fph (struct task_struct *task)
struct ia64_psr *psr = ia64_psr(ia64_task_regs(task));
+ /*
+ * Prevent migrating this task while
+ * we're fiddling with the FPU state
+ */
+ preempt_disable();
if (ia64_is_local_fpu_owner(task) && psr->mfh) {
psr->mfh = 0;
task->thread.flags |= IA64_THREAD_FPH_VALID;
+ preempt_enable();