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Message-Id: <200704052135.05043.kevcorry@us.ibm.com>
Date: Thu, 5 Apr 2007 21:35:04 -0500
From: Kevin Corry <kevcorry@...ibm.com>
To: Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...abs.org
Cc: LKML <linux-kernel@...r.kernel.org>, Carl Love <carll@...ibm.com>
Subject: Re: Questions about porting perfmon2 to powerpc
On Thu April 5 2007 3:32 pm, Kevin Corry wrote:
> On Thu April 5 2007 3:08 pm, Arnd Bergmann wrote:
> > On Thursday 05 April 2007, Kevin Corry wrote:
> > > First, the stock 2.6.20 kernel has a prototype in include/linux/smp.h
> > > for a function called smp_call_function_single(). However, this routine
> > > is only implemented on i386, x86_64, ia64, and mips. Perfmon2
> > > apparently needs to call this to run a function on a specific CPU.
> > > Powerpc provides an smp_call_function() routine to run a function on
> > > all active CPUs, so I used that as a basis to add an
> > > smp_call_function_single() routine. I've included the patch below and
> > > was wondering if it looked like a sane approach.
> >
> > The function itself looks good, but since it's very similar to the
> > existing smp_call_function(), you should probably try to share some of
> > the code, e.g. by making a helper function that gets an argument to
> > decide whether to run on a specific CPU or on all CPUs.
>
> Ok. I'll see what I can come up with and post another patch today or
> tomorrow.
Here's a new version that adds smp_call_function_single(), and moves the
code that's shared with smp_call_function() to __smp_call_function().
Thanks,
--
Kevin Corry
kevcorry@...ibm.com
http://www.ibm.com/linux/
Add an smp_call_function_single() to the powerpc architecture. Since this
is very similar to the existing smp_call_function() routine, the common
portions have been split out into __smp_call_function(). Since the
spin_lock(&call_lock) was moved to __smp_call_function(),
smp_call_function() now explicitly calls preempt_disable() before getting
the count of online CPUs.
Signed-off-by: Kevin Corry <kevcorry@...ibm.com>
Index: linux-2.6.20-arnd3-perfmon/arch/powerpc/kernel/smp.c
===================================================================
--- linux-2.6.20-arnd3-perfmon.orig/arch/powerpc/kernel/smp.c
+++ linux-2.6.20-arnd3-perfmon/arch/powerpc/kernel/smp.c
@@ -198,26 +198,11 @@ static struct call_data_struct {
/* delay of at least 8 seconds */
#define SMP_CALL_TIMEOUT 8
-/*
- * This function sends a 'generic call function' IPI to all other CPUs
- * in the system.
- *
- * [SUMMARY] Run a function on all other CPUs.
- * <func> The function to run. This must be fast and non-blocking.
- * <info> An arbitrary pointer to pass to the function.
- * <nonatomic> currently unused.
- * <wait> If true, wait (atomically) until function has completed on other CPUs.
- * [RETURNS] 0 on success, else a negative status code. Does not return until
- * remote CPUs are nearly ready to execute <<func>> or are or have executed.
- *
- * You must not call this function with disabled interrupts or from a
- * hardware interrupt handler or from a bottom half handler.
- */
-int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
- int wait)
-{
+static int __smp_call_function(void (*func)(void *info), void *info,
+ int wait, int target_cpu, int num_cpus)
+{
struct call_data_struct data;
- int ret = -1, cpus;
+ int ret = -1;
u64 timeout;
/* Can deadlock when called with interrupts disabled */
@@ -234,40 +219,33 @@ int smp_call_function (void (*func) (voi
atomic_set(&data.finished, 0);
spin_lock(&call_lock);
- /* Must grab online cpu count with preempt disabled, otherwise
- * it can change. */
- cpus = num_online_cpus() - 1;
- if (!cpus) {
- ret = 0;
- goto out;
- }
call_data = &data;
smp_wmb();
/* Send a message to all other CPUs and wait for them to respond */
- smp_ops->message_pass(MSG_ALL_BUT_SELF, PPC_MSG_CALL_FUNCTION);
+ smp_ops->message_pass(target_cpu, PPC_MSG_CALL_FUNCTION);
timeout = get_tb() + (u64) SMP_CALL_TIMEOUT * tb_ticks_per_sec;
/* Wait for response */
- while (atomic_read(&data.started) != cpus) {
+ while (atomic_read(&data.started) != num_cpus) {
HMT_low();
if (get_tb() >= timeout) {
- printk("smp_call_function on cpu %d: other cpus not "
- "responding (%d)\n", smp_processor_id(),
- atomic_read(&data.started));
+ printk("%s on cpu %d: other cpus not "
+ "responding (%d)\n", __FUNCTION__,
+ smp_processor_id(), atomic_read(&data.started));
debugger(NULL);
goto out;
}
}
if (wait) {
- while (atomic_read(&data.finished) != cpus) {
+ while (atomic_read(&data.finished) != num_cpus) {
HMT_low();
if (get_tb() >= timeout) {
- printk("smp_call_function on cpu %d: other "
- "cpus not finishing (%d/%d)\n",
- smp_processor_id(),
+ printk("%s on cpu %d: other cpus "
+ "not finishing (%d/%d)\n",
+ __FUNCTION__, smp_processor_id(),
atomic_read(&data.finished),
atomic_read(&data.started));
debugger(NULL);
@@ -285,8 +263,74 @@ int smp_call_function (void (*func) (voi
return ret;
}
+/*
+ * This function sends a 'generic call function' IPI to all other CPUs
+ * in the system.
+ *
+ * [SUMMARY] Run a function on all other CPUs.
+ * <func> The function to run. This must be fast and non-blocking.
+ * <info> An arbitrary pointer to pass to the function.
+ * <nonatomic> currently unused.
+ * <wait> If true, wait (atomically) until function has completed on other CPUs.
+ * [RETURNS] 0 on success, else a negative status code. Does not return until
+ * remote CPUs are nearly ready to execute <<func>> or are or have executed.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int smp_call_function (void (*func) (void *info), void *info, int nonatomic,
+ int wait)
+{
+ int num_cpus, ret = 0;
+
+ /* Must grab online cpu count with preempt disabled, otherwise
+ * it can change. */
+ preempt_disable();
+ num_cpus = num_online_cpus() - 1;
+ if (num_cpus) {
+ ret = __smp_call_function(func, info, wait,
+ MSG_ALL_BUT_SELF, num_cpus);
+ }
+ preempt_enable();
+ return ret;
+}
+
EXPORT_SYMBOL(smp_call_function);
+/*
+ * This function sends a 'generic call function' IPI to the specified CPU.
+ *
+ * [SUMMARY] Run a function on the specified CPUs.
+ * <cpuid> The CPU to run the function on.
+ * <func> The function to run. This must be fast and non-blocking.
+ * <info> An arbitrary pointer to pass to the function.
+ * <nonatomic> currently unused.
+ * <wait> If true, wait (atomically) until function has completed on the
+ * other CPU.
+ * [RETURNS] 0 on success, else a negative status code. Does not return until
+ * remote CPU is nearly ready to execute <<func>> or are or has executed.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler.
+ */
+int smp_call_function_single(int cpuid, void (*func)(void *info), void *info,
+ int nonatomic, int wait)
+{
+ int ret;
+
+ /* Prevent preemption and reschedule on another processor */
+ if (get_cpu() == cpuid) {
+ printk(KERN_INFO "%s: trying to call self\n", __FUNCTION__);
+ ret = -EBUSY;
+ } else
+ ret = __smp_call_function(func, info, wait, cpuid, 1);
+
+ put_cpu();
+ return ret;
+}
+
+EXPORT_SYMBOL(smp_call_function_single);
+
void smp_call_function_interrupt(void)
{
void (*func) (void *info);
-
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