| Message ID | 20230601143109.v9.4.I6d7f7d5fa0aa293c8c3374194947254b93114d37@changeid (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Add debug IPI for backtraces / kgdb; try to use NMI for it | expand |
On Thu, Jun 01, 2023 at 02:31:48PM -0700, Douglas Anderson wrote: > From: Sumit Garg <sumit.garg@linaro.org> > > All current arm64 interrupt controllers have at least 8 > IPIs. Currently we are only using 7 of them on arm64. Let's use the > 8th one as a debug IPI. This uses the new "debug IPI" infrastructure > which will try to allocate this IPI as an NMI/pseudo NMI if possible. > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > Signed-off-by: Douglas Anderson <dianders@chromium.org> I think with my suggestion on the prior patch, we don't need the additional logic here. > --- > I could imagine that people object to using up the last free IPI on > interrupt controllers with only 8 IPIs. However, it shouldn't be a big > deal. If we later need an extra IPI, it shouldn't be too hard to > combine some of the existing ones. Presumably we could just get rid of > the "crash stop" IPI and have the normal "stop" IPI do the crash if > "waiting_for_crash_ipi" is non-zero TBH, I'd love to unify the logic for IPI_CPU_STOP and IPI_CPU_CRASH_STOP as they have a bunch of pointless divergence. We could also remove IPI_WAKEUP and replace that with something else (e.g. IPI_CALL_FUNC with an empty function) in order to free up an IPI. I'd *also* prefer to have separate IPI_CPU_BACKTRACE and IPI_CPU_DEBUG as the backtrace logic is used for a bunch of things other than KGDB (e.g. RCU stalls, panic), and that would clearly separate the logic for the two cases. Thanks, Mark. > > Changes in v9: > - Add a warning if we don't have enough IPIs for the NMI IPI > - Renamed "NMI IPI" to "debug IPI" since it might not be backed by NMI. > - Update commit description > > Changes in v8: > - debug_ipi_setup() and debug_ipi_teardown() no longer take cpu param > > arch/arm64/kernel/smp.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index edd63894d61e..db019b49d3bd 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -53,6 +53,8 @@ > > #include <trace/events/ipi.h> > > +#include "ipi_debug.h" > + > DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number); > EXPORT_PER_CPU_SYMBOL(cpu_number); > > @@ -935,6 +937,8 @@ static void ipi_setup(int cpu) > > for (i = 0; i < nr_ipi; i++) > enable_percpu_irq(ipi_irq_base + i, 0); > + > + debug_ipi_setup(); > } > > #ifdef CONFIG_HOTPLUG_CPU > @@ -947,6 +951,8 @@ static void ipi_teardown(int cpu) > > for (i = 0; i < nr_ipi; i++) > disable_percpu_irq(ipi_irq_base + i); > + > + debug_ipi_teardown(); > } > #endif > > @@ -968,6 +974,11 @@ void __init set_smp_ipi_range(int ipi_base, int n) > irq_set_status_flags(ipi_base + i, IRQ_HIDDEN); > } > > + if (n > nr_ipi) > + set_smp_debug_ipi(ipi_base + nr_ipi); > + else > + WARN(1, "Not enough IPIs for NMI IPI\n"); > + > ipi_irq_base = ipi_base; > > /* Setup the boot CPU immediately */ > -- > 2.41.0.rc2.161.g9c6817b8e7-goog >
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index edd63894d61e..db019b49d3bd 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -53,6 +53,8 @@ #include <trace/events/ipi.h> +#include "ipi_debug.h" + DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number); EXPORT_PER_CPU_SYMBOL(cpu_number); @@ -935,6 +937,8 @@ static void ipi_setup(int cpu) for (i = 0; i < nr_ipi; i++) enable_percpu_irq(ipi_irq_base + i, 0); + + debug_ipi_setup(); } #ifdef CONFIG_HOTPLUG_CPU @@ -947,6 +951,8 @@ static void ipi_teardown(int cpu) for (i = 0; i < nr_ipi; i++) disable_percpu_irq(ipi_irq_base + i); + + debug_ipi_teardown(); } #endif @@ -968,6 +974,11 @@ void __init set_smp_ipi_range(int ipi_base, int n) irq_set_status_flags(ipi_base + i, IRQ_HIDDEN); } + if (n > nr_ipi) + set_smp_debug_ipi(ipi_base + nr_ipi); + else + WARN(1, "Not enough IPIs for NMI IPI\n"); + ipi_irq_base = ipi_base; /* Setup the boot CPU immediately */