On Sun, Jun 10, 2007 at 08:58:10PM -0500, Milton Miller wrote:
> The code is structured cleanly. However, when testing this patch, I
> found (1) you printed the mask as a cpulist instead of a cpumask.
> Since the user writes a cpumask to /proc/irq/xx/smp_affinity, it would
> make more sense to print a mask in the error message.
Attached patch uses cpumask_scnprintf function.
>
> However, this is all mute because (2) the common in /kenrel/irq/proc.c
> checks that a cpu in the mask is online and returns -EINVAL to the user
> without calling the ->set_affinity hook (we have no select_smp_affinity
> hook arch code). Unless there is another path to call ->set_affinity,
> we can only trigger the case of no online cpu by racing between setting
> the affinity and taking a cpu offline.
>
> Does anyone know of another path to set the affinity? If not I would
> remove this extra logic and change the behavior from ignore to set to
> default server.
>
tick_setup_device function in kernel/time/tick-common.c file calls
irq_set_affinity function without validating the new cpumask with the
cpu online mask. So IMHO the check in get_irq_server is required.
================
In some of the PPC970 based systems, interrupt would be distributed to
offline cpus also even when booted with "maxcpus=1". So check whether
cpu online map and cpu present map are equal or not. If they are equal
default_distrib_server is used as interrupt server otherwise boot cpu
(default_server) used as interrupt server.
In addition to this, if an interrupt is assigned to a specific cpu (ie
smp affinity) and if that cpu is not online, the earlier code used to
return the default_distrib_server as interrupt server. This patch
introduces an additional paramter to the get_irq function ie
strict_check, based on this parameter, if the cpu is not online either
default_distrib_server or -1 is returned.
Cc: Milton Miller <miltonm at bga.com>,
Michael Ellerman <michael at ellerman.id.au>
Signed-off-by: Mohan Kumar M <mohan at in.ibm.com>
---
arch/powerpc/platforms/pseries/xics.c | 53 ++++++++++++++++++----------------
1 file changed, 29 insertions(+), 24 deletions(-)
Index: linux-2.6.21.1/arch/powerpc/platforms/pseries/xics.c
===================================================================
--- linux-2.6.21.1.orig/arch/powerpc/platforms/pseries/xics.c
+++ linux-2.6.21.1/arch/powerpc/platforms/pseries/xics.c
@@ -156,9 +156,9 @@ static inline void lpar_qirr_info(int n_
#ifdef CONFIG_SMP
-static int get_irq_server(unsigned int virq)
+static int get_irq_server(unsigned int virq, unsigned int strict_check)
{
- unsigned int server;
+ int server;
/* For the moment only implement delivery to all cpus or one cpu */
cpumask_t cpumask = irq_desc[virq].affinity;
cpumask_t tmp = CPU_MASK_NONE;
@@ -166,22 +166,25 @@ static int get_irq_server(unsigned int v
if (!distribute_irqs)
return default_server;
- if (cpus_equal(cpumask, CPU_MASK_ALL)) {
- server = default_distrib_server;
- } else {
+ if (!cpus_equal(cpumask, CPU_MASK_ALL)) {
cpus_and(tmp, cpu_online_map, cpumask);
- if (cpus_empty(tmp))
- server = default_distrib_server;
- else
- server = get_hard_smp_processor_id(first_cpu(tmp));
+ server = first_cpu(tmp);
+
+ if (server < NR_CPUS)
+ return get_hard_smp_processor_id(server);
+
+ if (strict_check)
+ return -1;
}
- return server;
+ if (cpus_equal(cpu_online_map, cpu_present_map))
+ return default_distrib_server;
+ return default_server;
}
#else
-static int get_irq_server(unsigned int virq)
+static int get_irq_server(unsigned int virq, unsigned int strict_check)
{
return default_server;
}
@@ -192,7 +195,7 @@ static void xics_unmask_irq(unsigned int
{
unsigned int irq;
int call_status;
- unsigned int server;
+ int server;
pr_debug("xics: unmask virq %d\n", virq);
@@ -201,7 +204,7 @@ static void xics_unmask_irq(unsigned int
if (irq == XICS_IPI || irq == XICS_IRQ_SPURIOUS)
return;
- server = get_irq_server(virq);
+ server = get_irq_server(virq, 0);
call_status = rtas_call(ibm_set_xive, 3, 1, NULL, irq, server,
DEFAULT_PRIORITY);
@@ -398,8 +401,7 @@ static void xics_set_affinity(unsigned i
unsigned int irq;
int status;
int xics_status[2];
- unsigned long newmask;
- cpumask_t tmp = CPU_MASK_NONE;
+ int irq_server;
irq = (unsigned int)irq_map[virq].hwirq;
if (irq == XICS_IPI || irq == XICS_IRQ_SPURIOUS)
@@ -413,18 +415,21 @@ static void xics_set_affinity(unsigned i
return;
}
- /* For the moment only implement delivery to all cpus or one cpu */
- if (cpus_equal(cpumask, CPU_MASK_ALL)) {
- newmask = default_distrib_server;
- } else {
- cpus_and(tmp, cpu_online_map, cpumask);
- if (cpus_empty(tmp))
- return;
- newmask = get_hard_smp_processor_id(first_cpu(tmp));
+ /*
+ * For the moment only implement delivery to all cpus or one cpu.
+ * Get current irq_server for the given irq
+ */
+ irq_server = get_irq_server(irq, 1);
+ if (irq_server == -1) {
+ char cpulist[128];
+ cpumask_scnprintf(cpulist, sizeof(cpulist), cpumask);
+ printk(KERN_WARNING "xics_set_affinity: No online cpus in "
+ "the mask %s for irq %d\n", cpulist, virq);
+ return;
}
status = rtas_call(ibm_set_xive, 3, 1, NULL,
- irq, newmask, xics_status[1]);
+ irq, irq_server, xics_status[1]);
if (status) {
printk(KERN_ERR "xics_set_affinity: irq=%u ibm,set-xive "
