Messages in this thread Patch in this message | | | Subject | Re: [PATCH 2/2] arm64: factor work_pending state machine to C | From | Chris Metcalf <> | Date | Tue, 5 Jan 2016 13:53:03 -0500 |
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On 01/05/2016 12:33 PM, Mark Rutland wrote: > Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc > state machine that can be difficult to reason about due to duplicated > code and a large number of branch targets. > > This patch factors the common logic out into the existing > do_notify_resume function, converting the code to C in the process, > making the code more legible. > > This patch tries to mirror the existing behaviour as closely as possible > while using the usual C control flow primitives. There should be no > functional change as a result of this patch. > > Signed-off-by: Mark Rutland<mark.rutland@arm.com> > Cc: Catalin Marinas<catalin.marinas@arm.com> > Cc: Chris Metcalf<cmetcalf@ezchip.com> > Cc: Will Deacon<will.deacon@arm.com> > --- > arch/arm64/kernel/entry.S | 24 +++--------------------- > arch/arm64/kernel/signal.c | 36 ++++++++++++++++++++++++++---------- > 2 files changed, 29 insertions(+), 31 deletions(-)
This looks good, and also makes the task isolation change drop in very cleanly (relatively speaking). Since do_notify_resume() is called unconditionally now, we don't have to worry about fussing with the bit numbering for the TIF_xxx flags in asm/threadinfo.h, so that whole part of the patch can be dropped, and the actual change to do_notify_resume() becomes:
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 3a6c60beadca..00d0ec3a8e60 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -25,6 +25,7 @@ #include <linux/uaccess.h> #include <linux/tracehook.h> #include <linux/ratelimit.h> +#include <linux/isolation.h> #include <asm/debug-monitors.h> #include <asm/elf.h> @@ -408,7 +409,8 @@ asmlinkage void do_notify_resume(void) local_irq_disable(); thread_flags = READ_ONCE(current_thread_info()->flags); - if (!(thread_flags & _TIF_WORK_MASK)) + if (!(thread_flags & _TIF_WORK_MASK) && + task_isolation_ready()) break; if (thread_flags & _TIF_NEED_RESCHED) { @@ -428,5 +430,7 @@ asmlinkage void do_notify_resume(void) if (thread_flags & _TIF_FOREIGN_FPSTATE) fpsimd_restore_current_state(); + + task_isolation_enter(); } }
For the moment I just added your two commits into my task-isolation tree and pushed it up, but if your changes make it into 4.5 and the task-isolation series doesn't, I will remove them and rebase on 4.5-rc1 once that's released. I've similarly staged the arch/tile enablement changes to go into 4.5 so I can drop them from the task-isolation tree as well at that point.
-- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com
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