| From d8550860d910c6b7b70f830f59003b33daaa52c9 Mon Sep 17 00:00:00 2001 |
| From: Paul Burton <paul.burton@imgtec.com> |
| Date: Fri, 3 Mar 2017 15:26:05 -0800 |
| Subject: MIPS: Fix IRQ tracing & lockdep when rescheduling |
| |
| From: Paul Burton <paul.burton@imgtec.com> |
| |
| commit d8550860d910c6b7b70f830f59003b33daaa52c9 upstream. |
| |
| When the scheduler sets TIF_NEED_RESCHED & we call into the scheduler |
| from arch/mips/kernel/entry.S we disable interrupts. This is true |
| regardless of whether we reach work_resched from syscall_exit_work, |
| resume_userspace or by looping after calling schedule(). Although we |
| disable interrupts in these paths we don't call trace_hardirqs_off() |
| before calling into C code which may acquire locks, and we therefore |
| leave lockdep with an inconsistent view of whether interrupts are |
| disabled or not when CONFIG_PROVE_LOCKING & CONFIG_DEBUG_LOCKDEP are |
| both enabled. |
| |
| Without tracing this interrupt state lockdep will print warnings such |
| as the following once a task returns from a syscall via |
| syscall_exit_partial with TIF_NEED_RESCHED set: |
| |
| [ 49.927678] ------------[ cut here ]------------ |
| [ 49.934445] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3687 check_flags.part.41+0x1dc/0x1e8 |
| [ 49.946031] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) |
| [ 49.946355] CPU: 0 PID: 1 Comm: init Not tainted 4.10.0-00439-gc9fd5d362289-dirty #197 |
| [ 49.963505] Stack : 0000000000000000 ffffffff81bb5d6a 0000000000000006 ffffffff801ce9c4 |
| [ 49.974431] 0000000000000000 0000000000000000 0000000000000000 000000000000004a |
| [ 49.985300] ffffffff80b7e487 ffffffff80a24498 a8000000ff160000 ffffffff80ede8b8 |
| [ 49.996194] 0000000000000001 0000000000000000 0000000000000000 0000000077c8030c |
| [ 50.007063] 000000007fd8a510 ffffffff801cd45c 0000000000000000 a8000000ff127c88 |
| [ 50.017945] 0000000000000000 ffffffff801cf928 0000000000000001 ffffffff80a24498 |
| [ 50.028827] 0000000000000000 0000000000000001 0000000000000000 0000000000000000 |
| [ 50.039688] 0000000000000000 a8000000ff127bd0 0000000000000000 ffffffff805509bc |
| [ 50.050575] 00000000140084e0 0000000000000000 0000000000000000 0000000000040a00 |
| [ 50.061448] 0000000000000000 ffffffff8010e1b0 0000000000000000 ffffffff805509bc |
| [ 50.072327] ... |
| [ 50.076087] Call Trace: |
| [ 50.079869] [<ffffffff8010e1b0>] show_stack+0x80/0xa8 |
| [ 50.086577] [<ffffffff805509bc>] dump_stack+0x10c/0x190 |
| [ 50.093498] [<ffffffff8015dde0>] __warn+0xf0/0x108 |
| [ 50.099889] [<ffffffff8015de34>] warn_slowpath_fmt+0x3c/0x48 |
| [ 50.107241] [<ffffffff801c15b4>] check_flags.part.41+0x1dc/0x1e8 |
| [ 50.114961] [<ffffffff801c239c>] lock_is_held_type+0x8c/0xb0 |
| [ 50.122291] [<ffffffff809461b8>] __schedule+0x8c0/0x10f8 |
| [ 50.129221] [<ffffffff80946a60>] schedule+0x30/0x98 |
| [ 50.135659] [<ffffffff80106278>] work_resched+0x8/0x34 |
| [ 50.142397] ---[ end trace 0cb4f6ef5b99fe21 ]--- |
| [ 50.148405] possible reason: unannotated irqs-off. |
| [ 50.154600] irq event stamp: 400463 |
| [ 50.159566] hardirqs last enabled at (400463): [<ffffffff8094edc8>] _raw_spin_unlock_irqrestore+0x40/0xa8 |
| [ 50.171981] hardirqs last disabled at (400462): [<ffffffff8094eb98>] _raw_spin_lock_irqsave+0x30/0xb0 |
| [ 50.183897] softirqs last enabled at (400450): [<ffffffff8016580c>] __do_softirq+0x4ac/0x6a8 |
| [ 50.195015] softirqs last disabled at (400425): [<ffffffff80165e78>] irq_exit+0x110/0x128 |
| |
| Fix this by using the TRACE_IRQS_OFF macro to call trace_hardirqs_off() |
| when CONFIG_TRACE_IRQFLAGS is enabled. This is done before invoking |
| schedule() following the work_resched label because: |
| |
| 1) Interrupts are disabled regardless of the path we take to reach |
| work_resched() & schedule(). |
| |
| 2) Performing the tracing here avoids the need to do it in paths which |
| disable interrupts but don't call out to C code before hitting a |
| path which uses the RESTORE_SOME macro that will call |
| trace_hardirqs_on() or trace_hardirqs_off() as appropriate. |
| |
| We call trace_hardirqs_on() using the TRACE_IRQS_ON macro before calling |
| syscall_trace_leave() for similar reasons, ensuring that lockdep has a |
| consistent view of state after we re-enable interrupts. |
| |
| Signed-off-by: Paul Burton <paul.burton@imgtec.com> |
| Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") |
| Cc: linux-mips@linux-mips.org |
| Patchwork: https://patchwork.linux-mips.org/patch/15385/ |
| Signed-off-by: Ralf Baechle <ralf@linux-mips.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/mips/kernel/entry.S | 3 +++ |
| 1 file changed, 3 insertions(+) |
| |
| --- a/arch/mips/kernel/entry.S |
| +++ b/arch/mips/kernel/entry.S |
| @@ -11,6 +11,7 @@ |
| #include <asm/asm.h> |
| #include <asm/asmmacro.h> |
| #include <asm/compiler.h> |
| +#include <asm/irqflags.h> |
| #include <asm/regdef.h> |
| #include <asm/mipsregs.h> |
| #include <asm/stackframe.h> |
| @@ -119,6 +120,7 @@ work_pending: |
| andi t0, a2, _TIF_NEED_RESCHED # a2 is preloaded with TI_FLAGS |
| beqz t0, work_notifysig |
| work_resched: |
| + TRACE_IRQS_OFF |
| jal schedule |
| |
| local_irq_disable # make sure need_resched and |
| @@ -155,6 +157,7 @@ syscall_exit_work: |
| beqz t0, work_pending # trace bit set? |
| local_irq_enable # could let syscall_trace_leave() |
| # call schedule() instead |
| + TRACE_IRQS_ON |
| move a0, sp |
| jal syscall_trace_leave |
| b resume_userspace |