| Message ID | 20180605235305.GA72953@joelaf.mtv.corp.google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
On Tue, 2018-06-05 at 16:53 -0700, Joel Fernandes wrote: > (Resending since Andy wasn't on CC - sorry) > Andy, previously made some suggestions to this patch. The updated > version is > below and I am planning to send it along with this series as v9. I > have > included it in advance below for your Review. > > Andy, would you be Ok with adding your Reviewed-by to it? > FWIW, Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> P.S. I'm not familiar with the topic so much to have any insights about implementation, though. > ---8<----------------------- > > From: "Joel Fernandes (Google)" <joel@joelfernandes.org> > Date: Wed, 16 May 2018 23:46:06 -0700 > Subject: [PATCH v9 7/8] lib: Add module to simulate atomic sections > for testing > preemptoff tracers > > In this patch we introduce a test module for simulating a long atomic > section in the kernel which the preemptoff or irqsoff tracers can > detect. This module is to be used only for test purposes and is > default > disabled. > > Following is the expected output (only briefly shown) that can be > parsed > to verify that the tracers are working correctly. We will use this > from > the kselftests in future patches. > > For the preemptoff tracer: > > echo preemptoff > /d/tracing/current_tracer > sleep 1 > insmod ./test_atomic_sections.ko atomic_mode=preempt > atomic_time=500000 > sleep 1 > bash-4.3# cat /d/tracing/trace > preempt -1066 2...2 0us@: atomic_sect_run <-atomic_sect_run > preempt -1066 2...2 500002us : atomic_sect_run <-atomic_sect_run > preempt -1066 2...2 500004us : tracer_preempt_on <-atomic_sect_run > preempt -1066 2...2 500012us : <stack trace> > => kthread > => ret_from_fork > > For the irqsoff tracer: > > echo irqsoff > /d/tracing/current_tracer > sleep 1 > insmod ./test_atomic_sections.ko atomic_mode=irq atomic_time=500000 > sleep 1 > bash-4.3# cat /d/tracing/trace > irq dis -1069 1d..1 0us@: atomic_sect_run > irq dis -1069 1d..1 500001us : atomic_sect_run > irq dis -1069 1d..1 500002us : tracer_hardirqs_on <-atomic_sect_run > irq dis -1069 1d..1 500005us : <stack trace> > => ret_from_fork > > Co-developed-by: Erick Reyes <erickreyes@google.com> > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> > --- > lib/Kconfig.debug | 8 ++++ > lib/Makefile | 1 + > lib/test_atomic_sections.c | 77 > ++++++++++++++++++++++++++++++++++++++ > 3 files changed, 86 insertions(+) > create mode 100644 lib/test_atomic_sections.c > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index c40c7b734cd1..faebf0fe3bcf 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1933,6 +1933,14 @@ config TEST_KMOD > > If unsure, say N. > > +config TEST_ATOMIC_SECTIONS > + tristate "Simulate atomic sections for tracers to detect" > + depends on m > + help > + Select this option to build a test module that can help > test atomic > + sections by simulating them with a duration supplied as a > module > + parameter. Preempt disable and irq disable modes can be > requested. > + > config TEST_DEBUG_VIRTUAL > tristate "Test CONFIG_DEBUG_VIRTUAL feature" > depends on DEBUG_VIRTUAL > diff --git a/lib/Makefile b/lib/Makefile > index ce20696d5a92..e82cf5445b7b 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -46,6 +46,7 @@ obj-y += string_helpers.o > obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o > obj-y += hexdump.o > obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o > +obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o > obj-y += kstrtox.o > obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o > obj-$(CONFIG_TEST_BPF) += test_bpf.o > diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c > new file mode 100644 > index 000000000000..1eef518f0974 > --- /dev/null > +++ b/lib/test_atomic_sections.c > @@ -0,0 +1,77 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Atomic section emulation test module > + * > + * Emulates atomic sections by disabling IRQs or preemption > + * and doing a busy wait for a specified amount of time. > + * This can be used for testing of different atomic section > + * tracers such as irqsoff tracers. > + * > + * (c) 2018. Google LLC > + */ > + > +#include <linux/delay.h> > +#include <linux/interrupt.h> > +#include <linux/irq.h> > +#include <linux/kernel.h> > +#include <linux/kthread.h> > +#include <linux/ktime.h> > +#include <linux/module.h> > +#include <linux/printk.h> > +#include <linux/string.h> > + > +static ulong atomic_time = 100; > +static char atomic_mode[10] = "irq"; > + > +module_param_named(atomic_time, atomic_time, ulong, S_IRUGO); > +module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO); > +MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS > default)"); > +MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or > irq (default irq)"); > + > +static void busy_wait(ulong time) > +{ > + ktime_t start, end; > + start = ktime_get(); > + do { > + end = ktime_get(); > + if (kthread_should_stop()) > + break; > + } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); > +} > + > +int atomic_sect_run(void *data) > +{ > + unsigned long flags; > + > + if (!strcmp(atomic_mode, "irq")) { > + local_irq_save(flags); > + busy_wait(atomic_time); > + local_irq_restore(flags); > + } else if (!strcmp(atomic_mode, "preempt")) { > + preempt_disable(); > + busy_wait(atomic_time); > + preempt_enable(); > + } > + > + return 0; > +} > + > +static int __init atomic_sect_init(void) > +{ > + char task_name[50]; > + struct task_struct *test_task; > + > + snprintf(task_name, sizeof(task_name), "%s_test", > atomic_mode); > + > + test_task = kthread_run(atomic_sect_run, NULL, task_name); > + return PTR_ERR_OR_ZERO(test_task); > +} > + > +static void __exit atomic_sect_exit(void) > +{ > + return; > +} > + > +module_init(atomic_sect_init) > +module_exit(atomic_sect_exit) > +MODULE_LICENSE("GPL v2");
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index c40c7b734cd1..faebf0fe3bcf 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1933,6 +1933,14 @@ config TEST_KMOD If unsure, say N. +config TEST_ATOMIC_SECTIONS + tristate "Simulate atomic sections for tracers to detect" + depends on m + help + Select this option to build a test module that can help test atomic + sections by simulating them with a duration supplied as a module + parameter. Preempt disable and irq disable modes can be requested. + config TEST_DEBUG_VIRTUAL tristate "Test CONFIG_DEBUG_VIRTUAL feature" depends on DEBUG_VIRTUAL diff --git a/lib/Makefile b/lib/Makefile index ce20696d5a92..e82cf5445b7b 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -46,6 +46,7 @@ obj-y += string_helpers.o obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o obj-y += hexdump.o obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o +obj-$(CONFIG_TEST_ATOMIC_SECTIONS) += test_atomic_sections.o obj-y += kstrtox.o obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o obj-$(CONFIG_TEST_BPF) += test_bpf.o diff --git a/lib/test_atomic_sections.c b/lib/test_atomic_sections.c new file mode 100644 index 000000000000..1eef518f0974 --- /dev/null +++ b/lib/test_atomic_sections.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Atomic section emulation test module + * + * Emulates atomic sections by disabling IRQs or preemption + * and doing a busy wait for a specified amount of time. + * This can be used for testing of different atomic section + * tracers such as irqsoff tracers. + * + * (c) 2018. Google LLC + */ + +#include <linux/delay.h> +#include <linux/interrupt.h> +#include <linux/irq.h> +#include <linux/kernel.h> +#include <linux/kthread.h> +#include <linux/ktime.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/string.h> + +static ulong atomic_time = 100; +static char atomic_mode[10] = "irq"; + +module_param_named(atomic_time, atomic_time, ulong, S_IRUGO); +module_param_string(atomic_mode, atomic_mode, 10, S_IRUGO); +MODULE_PARM_DESC(atomic_time, "Period in microseconds (100 uS default)"); +MODULE_PARM_DESC(atomic_mode, "Mode of the test such as preempt or irq (default irq)"); + +static void busy_wait(ulong time) +{ + ktime_t start, end; + start = ktime_get(); + do { + end = ktime_get(); + if (kthread_should_stop()) + break; + } while (ktime_to_ns(ktime_sub(end, start)) < (time * 1000)); +} + +int atomic_sect_run(void *data) +{ + unsigned long flags; + + if (!strcmp(atomic_mode, "irq")) { + local_irq_save(flags); + busy_wait(atomic_time); + local_irq_restore(flags); + } else if (!strcmp(atomic_mode, "preempt")) { + preempt_disable(); + busy_wait(atomic_time); + preempt_enable(); + } + + return 0; +} + +static int __init atomic_sect_init(void) +{ + char task_name[50]; + struct task_struct *test_task; + + snprintf(task_name, sizeof(task_name), "%s_test", atomic_mode); + + test_task = kthread_run(atomic_sect_run, NULL, task_name); + return PTR_ERR_OR_ZERO(test_task); +} + +static void __exit atomic_sect_exit(void) +{ + return; +} + +module_init(atomic_sect_init) +module_exit(atomic_sect_exit) +MODULE_LICENSE("GPL v2");