From: Catalin Marinas catalin.marinas@arm.com

commit db3899a6477a4dccd26cbfb7f408b6be2cc068e0 upstream.

When a kernel is built with CONFIG_TRACE_IRQFLAGS the following warning is produced when entering userspace for the first time:

WARNING: at /work/Linux/linux-2.6-aarch64/kernel/locking/lockdep.c:3519 Modules linked in: CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc3+ #639 Hardware name: Juno (DT) task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000 PC is at check_flags.part.22+0x19c/0x1a8 LR is at check_flags.part.22+0x19c/0x1a8 pc : [<ffffffc0000fba6c>] lr : [<ffffffc0000fba6c>] pstate: 600001c5 sp : ffffffc9768abe10 x29: ffffffc9768abe10 x28: ffffffc9768a8000 x27: 0000000000000000 x26: 0000000000000001 x25: 00000000000000a6 x24: ffffffc00064be6c x23: ffffffc0009f249e x22: ffffffc9768a0000 x21: ffffffc97fea5480 x20: 00000000000001c0 x19: ffffffc00169a000 x18: 0000005558cc7b58 x17: 0000007fb78e3180 x16: 0000005558d2e238 x15: ffffffffffffffff x14: 0ffffffffffffffd x13: 0000000000000008 x12: 0101010101010101 x11: 7f7f7f7f7f7f7f7f x10: fefefefefefeff63 x9 : 7f7f7f7f7f7f7f7f x8 : 6e655f7371726964 x7 : 0000000000000001 x6 : ffffffc0001079c4 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffffffc001698438 x2 : 0000000000000000 x1 : ffffffc9768a0000 x0 : 000000000000002e Call trace: [<ffffffc0000fba6c>] check_flags.part.22+0x19c/0x1a8 [<ffffffc0000fc440>] lock_is_held+0x80/0x98 [<ffffffc00064bafc>] __schedule+0x404/0x730 [<ffffffc00064be6c>] schedule+0x44/0xb8 [<ffffffc000085bb0>] ret_to_user+0x0/0x24 possible reason: unannotated irqs-off. irq event stamp: 502169 hardirqs last enabled at (502169): [<ffffffc000085a98>] el0_irq_naked+0x1c/0x24 hardirqs last disabled at (502167): [<ffffffc0000bb3bc>] __do_softirq+0x17c/0x298 softirqs last enabled at (502168): [<ffffffc0000bb43c>] __do_softirq+0x1fc/0x298 softirqs last disabled at (502143): [<ffffffc0000bb830>] irq_exit+0xa0/0xf0

This happens because we disable interrupts in ret_to_user before calling schedule() in work_resched. This patch adds the necessary trace_hardirqs_off annotation.

Signed-off-by: Catalin Marinas catalin.marinas@arm.com Reported-by: Mark Rutland mark.rutland@arm.com Cc: Will Deacon will.deacon@arm.com Signed-off-by: Will Deacon will.deacon@arm.com --- Without this patch and CONFIG_TRACE_IRQFLAGS enabled, the mentioned warning is seen in v3.18.y and v4.4.y. The patch applies cleanly to both releases. I confirmed that the problem is gone after applying it.

arch/arm64/kernel/entry.S | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 7ed3d75f6304..e5b25389c48f 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -634,6 +634,9 @@ work_pending: bl do_notify_resume b ret_to_user work_resched: +#ifdef CONFIG_TRACE_IRQFLAGS + bl trace_hardirqs_off // the IRQs are off here, inform the tracing code +#endif bl schedule

/*