From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::147:1]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 8CD711A115A for ; Thu, 10 Dec 2015 20:45:06 +1100 (AEDT) Date: Thu, 10 Dec 2015 20:44:39 +1100 From: Anton Blanchard To: mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, cyrilbur@gmail.com, scottwood@freescale.com, mikey@neuling.org, linuxppc-dev@lists.ozlabs.org, Rashmica Subject: [PATCH v2] powerpc: Call restore_sprs() before _switch() Message-ID: <20151210204439.393ce017@kryten> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , commit 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()") moved the restore of SPRs after the call to _switch(). There is an issue with this approach - new tasks do not return through _switch(), they are set up by copy_thread() to directly return through ret_from_fork() or ret_from_kernel_thread(). This means restore_sprs() is not getting called for new tasks. Fix this by moving restore_sprs() before _switch(). Signed-off-by: Anton Blanchard Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()") fold --- arch/powerpc/kernel/process.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 58194c3..6f5c392 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -964,14 +964,17 @@ struct task_struct *__switch_to(struct task_struct *prev, tm_recheckpoint_new_task(new); - last = _switch(old_thread, new_thread); - - /* Need to recalculate these after calling _switch() */ - old_thread = &last->thread; - new_thread = ¤t->thread; - + /* + * Call restore_sprs() before calling _switch(). If we move it after + * _switch() then we miss out on calling it for new tasks. The reason + * for this is we manually create a stack frame for new tasks that + * directly returns through ret_from_fork() or + * ret_from_kernel_thread(). See copy_thread() for details. + */ restore_sprs(old_thread, new_thread); + last = _switch(old_thread, new_thread); + #ifdef CONFIG_PPC_BOOK3S_64 if (current_thread_info()->local_flags & _TLF_LAZY_MMU) { current_thread_info()->local_flags &= ~_TLF_LAZY_MMU; -- 2.5.0