From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <43BEBA0D.5090708@domain.hid> Date: Fri, 06 Jan 2006 20:42:21 +0200 From: Heikki Lindholm MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="------------080704050601020007070402" Subject: [Xenomai-core] [PATCH] Fix ppc fpu support List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xenomai@xenomai.org This is a multi-part message in MIME format. --------------080704050601020007070402 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Xenomai might preempt linux when linux has cleared a tasks MSR_FP, but not yet set last_task_used_math to NULL. As a result the tasks MSR_FP will get set, although it should be cleared. If the task happens to hit one of the codepaths that save FPU state if MSR_FP is set, the wrong FPU state might be saved to the task. The attached patch should fix this. I couldn't try it on most recent Xenomai trunk, because latency wouldn't build anymore. However, I see no reason it shouldn't work. All thee having trouble with X and Xenomai, give this a shot. -- Heikki Lindholm --------------080704050601020007070402 Content-Type: text/plain; x-mac-type="0"; x-mac-creator="0"; name="xenomai-060106-ppc-hwfpu.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="xenomai-060106-ppc-hwfpu.patch" diff -Nru xenomai/include/asm-powerpc/system.h xenomai-devel/include/asm-powerpc/system.h --- xenomai/include/asm-powerpc/system.h 2006-01-06 15:55:19.000000000 +0200 +++ xenomai-devel/include/asm-powerpc/system.h 2006-01-06 16:44:53.000000000 +0200 @@ -55,6 +55,7 @@ rthal_fpenv_t fpuenv __attribute__ ((aligned (16))); rthal_fpenv_t *fpup; /* Pointer to the FPU backup area */ struct task_struct *user_fpu_owner; + unsigned long user_fpu_owner_prev_msr; /* Pointer the the FPU owner in userspace: - NULL for RT K threads, - last_task_used_math for Linux US threads (only current or NULL when MP) @@ -368,7 +369,10 @@ rthal_save_fpu(tcb->fpup); if(tcb->user_fpu_owner && tcb->user_fpu_owner->thread.regs) + { + tcb->user_fpu_owner_prev_msr = tcb->user_fpu_owner->thread.regs->msr; tcb->user_fpu_owner->thread.regs->msr &= ~MSR_FP; + } } #endif /* CONFIG_XENO_HW_FPU */ @@ -383,7 +387,13 @@ { rthal_restore_fpu(tcb->fpup); - if(tcb->user_fpu_owner && tcb->user_fpu_owner->thread.regs) + /* Note: Only enable FP in MSR, if it was enabled when we saved the + * fpu state. We might have preempted Linux when it had disabled FP + * for the thread, but not yet set last_task_used_math to NULL + */ + if(tcb->user_fpu_owner && + tcb->user_fpu_owner->thread.regs && + ((tcb->user_fpu_owner_prev_msr & MSR_FP) != 0)) tcb->user_fpu_owner->thread.regs->msr |= MSR_FP; } --------------080704050601020007070402--