| Message ID | 20220918155246.1203293-7-guoren@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | riscv: Add GENERIC_ENTRY support and related features | expand |
On Sun, Sep 18, 2022 at 11:52:41AM -0400, guoren@kernel.org wrote: > From: Guo Ren <guoren@linux.alibaba.com> > > When DEBUG_PREEMPT=y, > exit_to_user_mode_prepare > ->tick_nohz_user_enter_prepare > ->tick_nohz_full_cpu(smp_processor_id()) > ->smp_processor_id() > ->debug_smp_processor_id() > ->check preempt_count() then: > > [ 5.717610] BUG: using smp_processor_id() in preemptible [00000000] > code: S20urandom/94 > [ 5.718111] caller is debug_smp_processor_id+0x24/0x38 > [ 5.718417] CPU: 1 PID: 94 Comm: S20urandom Not tainted > 6.0.0-rc3-00010-gfd0a0d619c63-dirty #238 > [ 5.718886] Hardware name: riscv-virtio,qemu (DT) > [ 5.719136] Call Trace: > [ 5.719281] [<ffffffff800055fc>] dump_backtrace+0x2c/0x3c > [ 5.719566] [<ffffffff80ae6cb0>] show_stack+0x44/0x5c > [ 5.720023] [<ffffffff80aee870>] dump_stack_lvl+0x74/0xa4 > [ 5.720557] [<ffffffff80aee8bc>] dump_stack+0x1c/0x2c > [ 5.721033] [<ffffffff80af65c0>] > check_preemption_disabled+0x104/0x108 > [ 5.721538] [<ffffffff80af65e8>] debug_smp_processor_id+0x24/0x38 > [ 5.722001] [<ffffffff800aee30>] exit_to_user_mode_prepare+0x48/0x178 > [ 5.722355] [<ffffffff80af5bf4>] irqentry_exit_to_user_mode+0x18/0x30 > [ 5.722685] [<ffffffff80af5c70>] irqentry_exit+0x64/0xa4 > [ 5.722953] [<ffffffff80af52f4>] do_page_fault+0x1d8/0x544 > [ 5.723291] [<ffffffff80003310>] ret_from_exception+0x0/0xb8 > > (Above is found in riscv platform with generic_entry) > > The smp_processor_id() needs irqs disable or preempt_disable, so use > preempt dis/in protecting the tick_nohz_user_enter_prepare(). > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > Signed-off-by: Guo Ren <guoren@kernel.org> > --- > kernel/entry/common.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > index 063068a9ea9b..36e4cd50531c 100644 > --- a/kernel/entry/common.c > +++ b/kernel/entry/common.c > @@ -194,8 +194,10 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) > > lockdep_assert_irqs_disabled(); Observe ^^^^ > > + preempt_disable(); > /* Flush pending rcuog wakeup before the last need_resched() check */ > tick_nohz_user_enter_prepare(); > + preempt_enable(); This makes no sense; if IRQs are disabled, check_preemption_disabled() should bail early per: if (irqs_disabled()) goto out;
On Mon, Sep 19, 2022 at 7:59 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Sun, Sep 18, 2022 at 11:52:41AM -0400, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > When DEBUG_PREEMPT=y, > > exit_to_user_mode_prepare > > ->tick_nohz_user_enter_prepare > > ->tick_nohz_full_cpu(smp_processor_id()) > > ->smp_processor_id() > > ->debug_smp_processor_id() > > ->check preempt_count() then: > > > > [ 5.717610] BUG: using smp_processor_id() in preemptible [00000000] > > code: S20urandom/94 > > [ 5.718111] caller is debug_smp_processor_id+0x24/0x38 > > [ 5.718417] CPU: 1 PID: 94 Comm: S20urandom Not tainted > > 6.0.0-rc3-00010-gfd0a0d619c63-dirty #238 > > [ 5.718886] Hardware name: riscv-virtio,qemu (DT) > > [ 5.719136] Call Trace: > > [ 5.719281] [<ffffffff800055fc>] dump_backtrace+0x2c/0x3c > > [ 5.719566] [<ffffffff80ae6cb0>] show_stack+0x44/0x5c > > [ 5.720023] [<ffffffff80aee870>] dump_stack_lvl+0x74/0xa4 > > [ 5.720557] [<ffffffff80aee8bc>] dump_stack+0x1c/0x2c > > [ 5.721033] [<ffffffff80af65c0>] > > check_preemption_disabled+0x104/0x108 > > [ 5.721538] [<ffffffff80af65e8>] debug_smp_processor_id+0x24/0x38 > > [ 5.722001] [<ffffffff800aee30>] exit_to_user_mode_prepare+0x48/0x178 > > [ 5.722355] [<ffffffff80af5bf4>] irqentry_exit_to_user_mode+0x18/0x30 > > [ 5.722685] [<ffffffff80af5c70>] irqentry_exit+0x64/0xa4 > > [ 5.722953] [<ffffffff80af52f4>] do_page_fault+0x1d8/0x544 > > [ 5.723291] [<ffffffff80003310>] ret_from_exception+0x0/0xb8 > > > > (Above is found in riscv platform with generic_entry) > > > > The smp_processor_id() needs irqs disable or preempt_disable, so use > > preempt dis/in protecting the tick_nohz_user_enter_prepare(). > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > --- > > kernel/entry/common.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > > index 063068a9ea9b..36e4cd50531c 100644 > > --- a/kernel/entry/common.c > > +++ b/kernel/entry/common.c > > @@ -194,8 +194,10 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) > > > > lockdep_assert_irqs_disabled(); > > Observe ^^^^ Thanks! I would enable PROVE_LOCKING for test. > > > > > + preempt_disable(); > > /* Flush pending rcuog wakeup before the last need_resched() check */ > > tick_nohz_user_enter_prepare(); > > + preempt_enable(); > > This makes no sense; if IRQs are disabled, check_preemption_disabled() > should bail early per: > > if (irqs_disabled()) > goto out; Ditto.
On Tue, Sep 20, 2022 at 9:45 AM Guo Ren <guoren@kernel.org> wrote: > > On Mon, Sep 19, 2022 at 7:59 PM Peter Zijlstra <peterz@infradead.org> wrote: > > > > On Sun, Sep 18, 2022 at 11:52:41AM -0400, guoren@kernel.org wrote: > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > > > When DEBUG_PREEMPT=y, > > > exit_to_user_mode_prepare > > > ->tick_nohz_user_enter_prepare > > > ->tick_nohz_full_cpu(smp_processor_id()) > > > ->smp_processor_id() > > > ->debug_smp_processor_id() > > > ->check preempt_count() then: > > > > > > [ 5.717610] BUG: using smp_processor_id() in preemptible [00000000] > > > code: S20urandom/94 > > > [ 5.718111] caller is debug_smp_processor_id+0x24/0x38 > > > [ 5.718417] CPU: 1 PID: 94 Comm: S20urandom Not tainted > > > 6.0.0-rc3-00010-gfd0a0d619c63-dirty #238 > > > [ 5.718886] Hardware name: riscv-virtio,qemu (DT) > > > [ 5.719136] Call Trace: > > > [ 5.719281] [<ffffffff800055fc>] dump_backtrace+0x2c/0x3c > > > [ 5.719566] [<ffffffff80ae6cb0>] show_stack+0x44/0x5c > > > [ 5.720023] [<ffffffff80aee870>] dump_stack_lvl+0x74/0xa4 > > > [ 5.720557] [<ffffffff80aee8bc>] dump_stack+0x1c/0x2c > > > [ 5.721033] [<ffffffff80af65c0>] > > > check_preemption_disabled+0x104/0x108 > > > [ 5.721538] [<ffffffff80af65e8>] debug_smp_processor_id+0x24/0x38 > > > [ 5.722001] [<ffffffff800aee30>] exit_to_user_mode_prepare+0x48/0x178 > > > [ 5.722355] [<ffffffff80af5bf4>] irqentry_exit_to_user_mode+0x18/0x30 > > > [ 5.722685] [<ffffffff80af5c70>] irqentry_exit+0x64/0xa4 > > > [ 5.722953] [<ffffffff80af52f4>] do_page_fault+0x1d8/0x544 > > > [ 5.723291] [<ffffffff80003310>] ret_from_exception+0x0/0xb8 > > > > > > (Above is found in riscv platform with generic_entry) > > > > > > The smp_processor_id() needs irqs disable or preempt_disable, so use > > > preempt dis/in protecting the tick_nohz_user_enter_prepare(). > > > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > > Signed-off-by: Guo Ren <guoren@kernel.org> > > > --- > > > kernel/entry/common.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > > > index 063068a9ea9b..36e4cd50531c 100644 > > > --- a/kernel/entry/common.c > > > +++ b/kernel/entry/common.c > > > @@ -194,8 +194,10 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) > > > > > > lockdep_assert_irqs_disabled(); > > > > Observe ^^^^ > Thanks! I would enable PROVE_LOCKING for test. It's my bug in page_fault, here is the solution: @@ -358,6 +358,8 @@ asmlinkage void noinstr do_page_fault(struct pt_regs *regs) __do_page_fault(regs); + local_irq_disable(); + irqentry_exit(regs, state); } NOKPROBE_SYMBOL(do_page_fault); > > > > > > > > > + preempt_disable(); > > > /* Flush pending rcuog wakeup before the last need_resched() check */ > > > tick_nohz_user_enter_prepare(); > > > + preempt_enable(); > > > > This makes no sense; if IRQs are disabled, check_preemption_disabled() > > should bail early per: > > > > if (irqs_disabled()) > > goto out; > Ditto. > > > -- > Best Regards > Guo Ren
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 063068a9ea9b..36e4cd50531c 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -194,8 +194,10 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) lockdep_assert_irqs_disabled(); + preempt_disable(); /* Flush pending rcuog wakeup before the last need_resched() check */ tick_nohz_user_enter_prepare(); + preempt_enable(); if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work);