| Message ID | 1455227590-9837-1-git-send-email-yang.shi@linaro.org |
|---|---|
| State | Accepted |
| Commit | a80a0eb70c358f8c7dda4bb62b2278dc6285217b |
| Headers | show |
On 2/12/2016 5:47 AM, James Morse wrote: > Hi! > > On 11/02/16 21:53, Yang Shi wrote: >> Switching between stacks is only valid if we are tracing ourselves while on the >> irq_stack, so it is only valid when in current and non-preemptible context, >> otherwise is is just zeroed off. > > Given it was picked up with CONFIG_DEBUG_PREEMPT: > > Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack") Wii add in v2. > > >> Signed-off-by: Yang Shi <yang.shi@linaro.org> >> --- >> arch/arm64/kernel/stacktrace.c | 13 ++++++------- >> arch/arm64/kernel/traps.c | 11 ++++++++++- >> 2 files changed, 16 insertions(+), 8 deletions(-) >> >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index 12a18cb..d9751a4 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) >> unsigned long irq_stack_ptr; >> >> /* >> - * Use raw_smp_processor_id() to avoid false-positives from >> - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping >> - * task stacks, we can be pre-empted in this case, so >> - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping >> - * tasks can't ever be on an interrupt stack, so regardless of cpu, >> - * the checks will always fail. >> + * Switching between stacks is valid when tracing current and in >> + * non-preemptible context. >> */ >> - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); >> + if (tsk == current && !preemptible()) >> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >> + else >> + irq_stack_ptr = 0; >> >> low = frame->sp; >> /* irq stacks are not THREAD_SIZE aligned */ >> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c >> index cbedd72..7d8db3a 100644 >> --- a/arch/arm64/kernel/traps.c >> +++ b/arch/arm64/kernel/traps.c >> @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) >> static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) >> { >> struct stackframe frame; >> - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >> + unsigned long irq_stack_ptr; >> int skip; >> >> + /* >> + * Switching between stacks is valid when tracing current and in > > Nit: Two spaces: "between[ ][ ]stacks" Will fix in v2. > > >> + * non-preemptible context. >> + */ >> + if (tsk == current && !preemptible()) >> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >> + else >> + irq_stack_ptr = 0; >> + >> pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); >> >> if (!tsk) >> > > Neither file includes 'linux/preempt.h' for the definition of preemptible(). > (I can't talk: I should have included smp.h for smp_processor_id()) I tried to build the kernel with preempt and without preempt, both works. And, I saw arch/arm64/include/asm/Kbuild has: generic-y += preempt.h So, it sounds preempt.h has been included by default. Thanks, Yang > > > Acked-by: James Morse <james.morse@arm.com> > Tested-by: James Morse <james.morse@arm.com> > > > Thanks! > > James > >
On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote: > On 2/12/2016 5:47 AM, James Morse wrote: > >On 11/02/16 21:53, Yang Shi wrote: > >>Switching between stacks is only valid if we are tracing ourselves while on the > >>irq_stack, so it is only valid when in current and non-preemptible context, > >>otherwise is is just zeroed off. > > > >Given it was picked up with CONFIG_DEBUG_PREEMPT: > > > >Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack") > > Wii add in v2. I already queued the patch with this and the whitespace fix, so no need for a v2. Will
On 2/12/2016 9:41 AM, Will Deacon wrote: > On Fri, Feb 12, 2016 at 09:38:51AM -0800, Shi, Yang wrote: >> On 2/12/2016 5:47 AM, James Morse wrote: >>> On 11/02/16 21:53, Yang Shi wrote: >>>> Switching between stacks is only valid if we are tracing ourselves while on the >>>> irq_stack, so it is only valid when in current and non-preemptible context, >>>> otherwise is is just zeroed off. >>> >>> Given it was picked up with CONFIG_DEBUG_PREEMPT: >>> >>> Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with irq_stack") >> >> Wii add in v2. > > I already queued the patch with this and the whitespace fix, so no need > for a v2. Thanks so much. Yang > > Will >
On 2/12/2016 9:38 AM, Shi, Yang wrote: > On 2/12/2016 5:47 AM, James Morse wrote: >> Hi! >> >> On 11/02/16 21:53, Yang Shi wrote: >>> Switching between stacks is only valid if we are tracing ourselves >>> while on the >>> irq_stack, so it is only valid when in current and non-preemptible >>> context, >>> otherwise is is just zeroed off. >> >> Given it was picked up with CONFIG_DEBUG_PREEMPT: >> >> Fixes: 132cd887b5c5 ("arm64: Modify stack trace and dump for use with >> irq_stack") > > Wii add in v2. > >> >> >>> Signed-off-by: Yang Shi <yang.shi@linaro.org> >>> --- >>> arch/arm64/kernel/stacktrace.c | 13 ++++++------- >>> arch/arm64/kernel/traps.c | 11 ++++++++++- >>> 2 files changed, 16 insertions(+), 8 deletions(-) >>> >>> diff --git a/arch/arm64/kernel/stacktrace.c >>> b/arch/arm64/kernel/stacktrace.c >>> index 12a18cb..d9751a4 100644 >>> --- a/arch/arm64/kernel/stacktrace.c >>> +++ b/arch/arm64/kernel/stacktrace.c >>> @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, >>> struct stackframe *frame) >>> unsigned long irq_stack_ptr; >>> >>> /* >>> - * Use raw_smp_processor_id() to avoid false-positives from >>> - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on >>> sleeping >>> - * task stacks, we can be pre-empted in this case, so >>> - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping >>> - * tasks can't ever be on an interrupt stack, so regardless of cpu, >>> - * the checks will always fail. >>> + * Switching between stacks is valid when tracing current and in >>> + * non-preemptible context. >>> */ >>> - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); >>> + if (tsk == current && !preemptible()) >>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >>> + else >>> + irq_stack_ptr = 0; >>> >>> low = frame->sp; >>> /* irq stacks are not THREAD_SIZE aligned */ >>> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c >>> index cbedd72..7d8db3a 100644 >>> --- a/arch/arm64/kernel/traps.c >>> +++ b/arch/arm64/kernel/traps.c >>> @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct >>> pt_regs *regs) >>> static void dump_backtrace(struct pt_regs *regs, struct task_struct >>> *tsk) >>> { >>> struct stackframe frame; >>> - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >>> + unsigned long irq_stack_ptr; >>> int skip; >>> >>> + /* >>> + * Switching between stacks is valid when tracing current and in >> >> Nit: Two spaces: "between[ ][ ]stacks" > > Will fix in v2. > >> >> >>> + * non-preemptible context. >>> + */ >>> + if (tsk == current && !preemptible()) >>> + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); >>> + else >>> + irq_stack_ptr = 0; >>> + >>> pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); >>> >>> if (!tsk) >>> >> >> Neither file includes 'linux/preempt.h' for the definition of >> preemptible(). >> (I can't talk: I should have included smp.h for smp_processor_id()) > > I tried to build the kernel with preempt and without preempt, both > works. And, I saw arch/arm64/include/asm/Kbuild has: > > generic-y += preempt.h > > So, it sounds preempt.h has been included by default. In addition, linux/sched.h, which is included by both traps.c and stacktrace.c, includes preempt.h already. Yang > > Thanks, > Yang > >> >> >> Acked-by: James Morse <james.morse@arm.com> >> Tested-by: James Morse <james.morse@arm.com> >> >> >> Thanks! >> >> James >> >> >
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 12a18cb..d9751a4 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,14 +44,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long irq_stack_ptr; /* - * Use raw_smp_processor_id() to avoid false-positives from - * CONFIG_DEBUG_PREEMPT. get_wchan() calls unwind_frame() on sleeping - * task stacks, we can be pre-empted in this case, so - * {raw_,}smp_processor_id() may give us the wrong value. Sleeping - * tasks can't ever be on an interrupt stack, so regardless of cpu, - * the checks will always fail. + * Switching between stacks is valid when tracing current and in + * non-preemptible context. */ - irq_stack_ptr = IRQ_STACK_PTR(raw_smp_processor_id()); + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0; low = frame->sp; /* irq stacks are not THREAD_SIZE aligned */ diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index cbedd72..7d8db3a 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -146,9 +146,18 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; - unsigned long irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + unsigned long irq_stack_ptr; int skip; + /* + * Switching between stacks is valid when tracing current and in + * non-preemptible context. + */ + if (tsk == current && !preemptible()) + irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id()); + else + irq_stack_ptr = 0; + pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); if (!tsk)
Switching between stacks is only valid if we are tracing ourselves while on the irq_stack, so it is only valid when in current and non-preemptible context, otherwise is is just zeroed off. Signed-off-by: Yang Shi <yang.shi@linaro.org> --- arch/arm64/kernel/stacktrace.c | 13 ++++++------- arch/arm64/kernel/traps.c | 11 ++++++++++- 2 files changed, 16 insertions(+), 8 deletions(-) -- 2.0.2