| Message ID | 1452015215-29506-1-git-send-email-mark.rutland@arm.com |
|---|---|
| State | Accepted |
| Commit | ee03353bc04f8e460cc4e3da80d9721d9ecb89f1 |
| Headers | show |
On Tue, Jan 05, 2016 at 05:33:34PM +0000, Mark Rutland wrote: > In work_pending we may skip work if the stacked SPSR value represents > anything other than an EL0 context. We then immediately invoke the > kernel_exit 0 macro as part of ret_to_user, assuming a return to EL0. > This is somewhat confusing. > > We use work_pending as part of the ret_to_user/ret_fast_syscall state > machine. We only use ret_fast_syscall in the return from an SVC issued > from EL0. We use ret_to_user for return from EL0 exception handlers and > also for return from ret_from_fork in the case the task was not a kernel > thread (i.e. it is a user task). > > Thus in all cases the stacked SPSR value must represent an EL0 context, > and the check is redundant. This patch removes it, along with the now > unused no_work_pending label. > > 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> Acked-by: Catalin Marinas <catalin.marinas@arm.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 7ed3d75..6b30ab1 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -626,10 +626,7 @@ ret_fast_syscall_trace: work_pending: tbnz x1, #TIF_NEED_RESCHED, work_resched /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */ - ldr x2, [sp, #S_PSTATE] mov x0, sp // 'regs' - tst x2, #PSR_MODE_MASK // user mode regs? - b.ne no_work_pending // returning to kernel enable_irq // enable interrupts for do_notify_resume() bl do_notify_resume b ret_to_user @@ -645,7 +642,6 @@ ret_to_user: and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending enable_step_tsk x1, x2 -no_work_pending: kernel_exit 0 ENDPROC(ret_to_user)
In work_pending we may skip work if the stacked SPSR value represents anything other than an EL0 context. We then immediately invoke the kernel_exit 0 macro as part of ret_to_user, assuming a return to EL0. This is somewhat confusing. We use work_pending as part of the ret_to_user/ret_fast_syscall state machine. We only use ret_fast_syscall in the return from an SVC issued from EL0. We use ret_to_user for return from EL0 exception handlers and also for return from ret_from_fork in the case the task was not a kernel thread (i.e. it is a user task). Thus in all cases the stacked SPSR value must represent an EL0 context, and the check is redundant. This patch removes it, along with the now unused no_work_pending label. 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 | 4 ---- 1 file changed, 4 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/