On Mon, Apr 15, 2013 at 11:45:42AM +0100, Will Deacon wrote: > On Mon, Apr 15, 2013 at 11:11:59AM +0100, Catalin Marinas wrote: > > 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 <cov@xxxxxxxxxxxxxx> > > > --- > > > 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. > > Really? If prev is NULL in context_switch(...), the scheduler will implode, > and I can't see where else switch_to is called from. > > Which code path are you thinking of? copy_thread() zeros cpu_context which is used by cpu_switch_to() to load the next saved registers. The switch_to() function sets prev to last as returned by __switch_to(), so this is valid but in __switch_to() we don't have a valid prev (nor next) after cpu_switch_to() for newly created threads. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
