From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Mon, 15 Apr 2013 11:11:59 +0100 Subject: [PATCH v2] arm64: Fix task tracing In-Reply-To: <1365510814-21343-1-git-send-email-cov@codeaurora.org> References: <20130408153132.GQ17476@mudshark.cambridge.arm.com> <1365510814-21343-1-git-send-email-cov@codeaurora.org> Message-ID: <20130415101159.GA25095@localhost.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Apr 09, 2013 at 01:33:34PM +0100, Christopher Covington wrote: > For accurate accounting pass contextidr_thread_switch the prev > task pointer, since cpu_switch_to has at that point changed the > the stack pointer. > > Signed-off-by: Christopher Covington > --- > arch/arm64/kernel/process.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 0337cdb..a49b25a 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -315,7 +315,7 @@ struct task_struct *__switch_to(struct task_struct *prev, > /* the actual thread switch */ > last = cpu_switch_to(prev, next); > > - contextidr_thread_switch(next); > + contextidr_thread_switch(prev); The original code was indeed wrong but using prev isn't any better. For a newly created thread, prev is probably 0 (if it's in a register, cpu_context has been zeroed by copy_thread()) or some random stack value. So we either use current or move the call before cpu_switch_to() (I would go for the former). -- Catalin