From: Andrew Bresticker abrestic@rivosinc.com
[ Upstream commit b0f4c74eadbf69a3298f38566bfaa2e202541f2f ]
The return to userspace path in entry.S may enable interrupts without the corresponding lockdep annotation, producing a splat[0] when DEBUG_LOCKDEP is enabled. Simply calling __trace_hardirqs_on() here gets a bit messy due to the use of RA to point back to ret_from_exception, so just move the whole slow-path loop into C. It's more readable and it lets us use local_irq_{enable,disable}(), avoiding the need for manual annotations altogether.
[0]: ------------[ cut here ]------------ DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled()) WARNING: CPU: 2 PID: 1 at kernel/locking/lockdep.c:5512 check_flags+0x10a/0x1e0 Modules linked in: CPU: 2 PID: 1 Comm: init Not tainted 6.1.0-rc4-00160-gb56b6e2b4f31 #53 Hardware name: riscv-virtio,qemu (DT) epc : check_flags+0x10a/0x1e0 ra : check_flags+0x10a/0x1e0 <snip> status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003 [<ffffffff808edb90>] lock_is_held_type+0x78/0x14e [<ffffffff8003dae2>] __might_resched+0x26/0x22c [<ffffffff8003dd24>] __might_sleep+0x3c/0x66 [<ffffffff80022c60>] get_signal+0x9e/0xa70 [<ffffffff800054a2>] do_notify_resume+0x6e/0x422 [<ffffffff80003c68>] ret_from_exception+0x0/0x10 irq event stamp: 44512 hardirqs last enabled at (44511): [<ffffffff808f901c>] _raw_spin_unlock_irqrestore+0x54/0x62 hardirqs last disabled at (44512): [<ffffffff80008200>] __trace_hardirqs_off+0xc/0x14 softirqs last enabled at (44472): [<ffffffff808f9fbe>] __do_softirq+0x3de/0x51e softirqs last disabled at (44467): [<ffffffff80017760>] irq_exit+0xd6/0x104 ---[ end trace 0000000000000000 ]--- possible reason: unannotated irqs-on.
Signed-off-by: Andrew Bresticker abrestic@rivosinc.com Fixes: 3c4697982982 ("riscv: Enable LOCKDEP_SUPPORT & fixup TRACE_IRQFLAGS_SUPPORT") Link: https://lore.kernel.org/r/20221111223108.1976562-1-abrestic@rivosinc.com Signed-off-by: Palmer Dabbelt palmer@rivosinc.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kernel/entry.S | 18 +++++------------- arch/riscv/kernel/signal.c | 34 +++++++++++++++++++++------------- 2 files changed, 26 insertions(+), 26 deletions(-)
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 186abd146eaf..3221a9e5f372 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -263,12 +263,11 @@ ret_from_exception: #endif bnez s0, resume_kernel
-resume_userspace: /* Interrupts must be disabled here so flags are checked atomically */ REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */ andi s1, s0, _TIF_WORK_MASK - bnez s1, work_pending - + bnez s1, resume_userspace_slow +resume_userspace: #ifdef CONFIG_CONTEXT_TRACKING_USER call user_enter_callable #endif @@ -368,19 +367,12 @@ resume_kernel: j restore_all #endif
-work_pending: +resume_userspace_slow: /* Enter slow path for supplementary processing */ - la ra, ret_from_exception - andi s1, s0, _TIF_NEED_RESCHED - bnez s1, work_resched -work_notifysig: - /* Handle pending signals and notify-resume requests */ - csrs CSR_STATUS, SR_IE /* Enable interrupts for do_notify_resume() */ move a0, sp /* pt_regs */ move a1, s0 /* current_thread_info->flags */ - tail do_notify_resume -work_resched: - tail schedule + call do_work_pending + j resume_userspace
/* Slow paths for ptrace. */ handle_syscall_trace_enter: diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 5c591123c440..bfb2afa4135f 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -313,19 +313,27 @@ static void do_signal(struct pt_regs *regs) }
/* - * notification of userspace execution resumption - * - triggered by the _TIF_WORK_MASK flags + * Handle any pending work on the resume-to-userspace path, as indicated by + * _TIF_WORK_MASK. Entered from assembly with IRQs off. */ -asmlinkage __visible void do_notify_resume(struct pt_regs *regs, - unsigned long thread_info_flags) +asmlinkage __visible void do_work_pending(struct pt_regs *regs, + unsigned long thread_info_flags) { - if (thread_info_flags & _TIF_UPROBE) - uprobe_notify_resume(regs); - - /* Handle pending signal delivery */ - if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) - do_signal(regs); - - if (thread_info_flags & _TIF_NOTIFY_RESUME) - resume_user_mode_work(regs); + do { + if (thread_info_flags & _TIF_NEED_RESCHED) { + schedule(); + } else { + local_irq_enable(); + if (thread_info_flags & _TIF_UPROBE) + uprobe_notify_resume(regs); + /* Handle pending signal delivery */ + if (thread_info_flags & (_TIF_SIGPENDING | + _TIF_NOTIFY_SIGNAL)) + do_signal(regs); + if (thread_info_flags & _TIF_NOTIFY_RESUME) + resume_user_mode_work(regs); + } + local_irq_disable(); + thread_info_flags = read_thread_flags(); + } while (thread_info_flags & _TIF_WORK_MASK); }