* [PATCH v3] riscv: don't stop itself in smp_send_stop
@ 2018-12-17 9:47 Andreas Schwab
2018-12-17 18:36 ` Christoph Hellwig
0 siblings, 1 reply; 3+ messages in thread
From: Andreas Schwab @ 2018-12-17 9:47 UTC (permalink / raw)
To: linux-riscv
Add IPI_CPU_STOP message and use it in smp_send_stop to stop other cpus,
but not itself. Mark cpu offline on reception of IPI_CPU_STOP.
Signed-off-by: Andreas Schwab <schwab@suse.de>
---
v3: minor fixes
---
arch/riscv/kernel/smp.c | 43 ++++++++++++++++++++++++++++++++++-------
1 file changed, 36 insertions(+), 7 deletions(-)
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 57b1383e5e..d0bd3f1187 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -23,6 +23,7 @@
#include <linux/smp.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
+#include <linux/delay.h>
#include <asm/sbi.h>
#include <asm/tlbflush.h>
@@ -31,6 +32,7 @@
enum ipi_message_type {
IPI_RESCHEDULE,
IPI_CALL_FUNC,
+ IPI_CPU_STOP,
IPI_MAX
};
@@ -66,6 +68,13 @@ int setup_profiling_timer(unsigned int multiplier)
return -EINVAL;
}
+static void ipi_stop(void)
+{
+ set_cpu_online(smp_processor_id(), false);
+ while (1)
+ wait_for_interrupt();
+}
+
void riscv_software_interrupt(void)
{
unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
@@ -94,6 +103,11 @@ void riscv_software_interrupt(void)
generic_smp_call_function_interrupt();
}
+ if (ops & (1 << IPI_CPU_STOP)) {
+ stats[IPI_CPU_STOP]++;
+ ipi_stop();
+ }
+
BUG_ON((ops >> IPI_MAX) != 0);
/* Order data access and bit testing. */
@@ -121,6 +135,7 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
static const char * const ipi_names[] = {
[IPI_RESCHEDULE] = "Rescheduling interrupts",
[IPI_CALL_FUNC] = "Function call interrupts",
+ [IPI_CPU_STOP] = "CPU stop interrupts",
};
void show_ipi_stats(struct seq_file *p, int prec)
@@ -146,15 +161,29 @@ void arch_send_call_function_single_ipi(int cpu)
send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
}
-static void ipi_stop(void *unused)
-{
- while (1)
- wait_for_interrupt();
-}
-
void smp_send_stop(void)
{
- on_each_cpu(ipi_stop, NULL, 1);
+ unsigned long timeout;
+
+ if (num_online_cpus() > 1) {
+ cpumask_t mask;
+
+ cpumask_copy(&mask, cpu_online_mask);
+ cpumask_clear_cpu(smp_processor_id(), &mask);
+
+ if (system_state <= SYSTEM_RUNNING)
+ pr_crit("SMP: stopping secondary CPUs\n");
+ send_ipi_message(&mask, IPI_CPU_STOP);
+ }
+
+ /* Wait up to one second for other CPUs to stop */
+ timeout = USEC_PER_SEC;
+ while (num_online_cpus() > 1 && timeout--)
+ udelay(1);
+
+ if (num_online_cpus() > 1)
+ pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
+ cpumask_pr_args(cpu_online_mask));
}
void smp_send_reschedule(int cpu)
--
2.20.0
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] riscv: don't stop itself in smp_send_stop
2018-12-17 9:47 [PATCH v3] riscv: don't stop itself in smp_send_stop Andreas Schwab
@ 2018-12-17 18:36 ` Christoph Hellwig
2018-12-18 8:50 ` Andreas Schwab
0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2018-12-17 18:36 UTC (permalink / raw)
To: Andreas Schwab; +Cc: linux-riscv
> void smp_send_stop(void)
> {
> - on_each_cpu(ipi_stop, NULL, 1);
> + unsigned long timeout;
> +
> + if (num_online_cpus() > 1) {
> + cpumask_t mask;
> +
> + cpumask_copy(&mask, cpu_online_mask);
> + cpumask_clear_cpu(smp_processor_id(), &mask);
> +
> + if (system_state <= SYSTEM_RUNNING)
> + pr_crit("SMP: stopping secondary CPUs\n");
> + send_ipi_message(&mask, IPI_CPU_STOP);
> + }
> +
> + /* Wait up to one second for other CPUs to stop */
> + timeout = USEC_PER_SEC;
> + while (num_online_cpus() > 1 && timeout--)
> + udelay(1);
> +
> + if (num_online_cpus() > 1)
> + pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
> + cpumask_pr_args(cpu_online_mask));
Given that this function doesn't mark the current CPU as not offline
it seems we could just exit early for num_online_cpus() == 1?
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] riscv: don't stop itself in smp_send_stop
2018-12-17 18:36 ` Christoph Hellwig
@ 2018-12-18 8:50 ` Andreas Schwab
0 siblings, 0 replies; 3+ messages in thread
From: Andreas Schwab @ 2018-12-18 8:50 UTC (permalink / raw)
To: Christoph Hellwig; +Cc: linux-riscv
On Dez 17 2018, Christoph Hellwig <hch@infradead.org> wrote:
>> void smp_send_stop(void)
>> {
>> - on_each_cpu(ipi_stop, NULL, 1);
>> + unsigned long timeout;
>> +
>> + if (num_online_cpus() > 1) {
>> + cpumask_t mask;
>> +
>> + cpumask_copy(&mask, cpu_online_mask);
>> + cpumask_clear_cpu(smp_processor_id(), &mask);
>> +
>> + if (system_state <= SYSTEM_RUNNING)
>> + pr_crit("SMP: stopping secondary CPUs\n");
>> + send_ipi_message(&mask, IPI_CPU_STOP);
>> + }
>> +
>> + /* Wait up to one second for other CPUs to stop */
>> + timeout = USEC_PER_SEC;
>> + while (num_online_cpus() > 1 && timeout--)
>> + udelay(1);
>> +
>> + if (num_online_cpus() > 1)
>> + pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
>> + cpumask_pr_args(cpu_online_mask));
>
> Given that this function doesn't mark the current CPU as not offline
> it seems we could just exit early for num_online_cpus() == 1?
So much for copying existing implementations.
The only difference it would make is two less calls to num_online_cpus
on a single cpu system. Hardly worth it, IMHO.
Andreas.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-12-18 8:51 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-12-17 9:47 [PATCH v3] riscv: don't stop itself in smp_send_stop Andreas Schwab
2018-12-17 18:36 ` Christoph Hellwig
2018-12-18 8:50 ` Andreas Schwab
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).