| Message ID | 1309372300-28911-1-git-send-email-sboyd@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 29, 2011 at 11:31:39AM -0700, Stephen Boyd wrote: > If an ARM system has multiple cpus in the same socket and the > kernel is booted with maxcpus=1, secondary cpus are possible but > not present due to how platform_smp_prepare_cpus() is called. > Fix this by always calling platform_smp_prepare_cpus() as long as > max_cpus is non-zero (0 means no SMP) to allow platform code to > decide if any non-boot cpus are present in the system. Since > all current platform code doesn't support physical hotplug we > have a situation where possible == present and thus we can > simply copy the possible map to the present map. > > With this patch it's possible to boot an ARM system with > maxcpus=1 on the command line and then hotplug in secondary cpus > via sysfs. This is more in line with how x86 works with maxcpus=1 > on the command line. > > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Paul Mundt <lethal@linux-sh.org>
On 6/30/2011 6:11 AM, Russell King - ARM Linux wrote: > On Wed, Jun 29, 2011 at 11:31:39AM -0700, Stephen Boyd wrote: >> void __init platform_smp_prepare_cpus(unsigned int max_cpus) >> { >> - int i; >> - >> /* >> * Initialise the present map, which describes the set of CPUs >> * actually populated at the present time. >> */ >> - for (i = 0; i < max_cpus; i++) >> - set_cpu_present(i, true); >> + init_cpu_present(&cpu_possible_map); > Ok, if we're now doing this in every platform, it might as well go into > arch/arm/kernel/smp.c - platforms can re-initialize the present map > in this callback if they need to do something different. That sounds better. V2 coming soon.
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index e7f92a4..fbaa24a 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -365,8 +365,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus) */ if (max_cpus > ncores) max_cpus = ncores; - - if (max_cpus > 1) { + if (ncores > 1 && max_cpus) { /* * Enable the local timer or broadcast device for the * boot CPU, but only if we have more than one CPU. diff --git a/arch/arm/mach-exynos4/platsmp.c b/arch/arm/mach-exynos4/platsmp.c index c5e65a0..3f870d2 100644 --- a/arch/arm/mach-exynos4/platsmp.c +++ b/arch/arm/mach-exynos4/platsmp.c @@ -154,14 +154,11 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); scu_enable(scu_base_addr()); diff --git a/arch/arm/mach-msm/platsmp.c b/arch/arm/mach-msm/platsmp.c index 2034098..84e293f 100644 --- a/arch/arm/mach-msm/platsmp.c +++ b/arch/arm/mach-msm/platsmp.c @@ -157,12 +157,9 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); } diff --git a/arch/arm/mach-omap2/omap-smp.c b/arch/arm/mach-omap2/omap-smp.c index ecfe93c..5895d19 100644 --- a/arch/arm/mach-omap2/omap-smp.c +++ b/arch/arm/mach-omap2/omap-smp.c @@ -125,14 +125,11 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); /* * Initialise the SCU and wake up the secondary core using diff --git a/arch/arm/mach-realview/platsmp.c b/arch/arm/mach-realview/platsmp.c index 963bf0d..00666be 100644 --- a/arch/arm/mach-realview/platsmp.c +++ b/arch/arm/mach-realview/platsmp.c @@ -68,14 +68,11 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); scu_enable(scu_base_addr()); diff --git a/arch/arm/mach-shmobile/platsmp.c b/arch/arm/mach-shmobile/platsmp.c index f3888fe..ca5b523 100644 --- a/arch/arm/mach-shmobile/platsmp.c +++ b/arch/arm/mach-shmobile/platsmp.c @@ -64,10 +64,7 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); shmobile_smp_prepare_cpus(); } diff --git a/arch/arm/mach-tegra/platsmp.c b/arch/arm/mach-tegra/platsmp.c index b8ae3c9..f11426a 100644 --- a/arch/arm/mach-tegra/platsmp.c +++ b/arch/arm/mach-tegra/platsmp.c @@ -129,14 +129,11 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); scu_enable(scu_base); } diff --git a/arch/arm/mach-ux500/platsmp.c b/arch/arm/mach-ux500/platsmp.c index 0c527fe..4509b7d 100644 --- a/arch/arm/mach-ux500/platsmp.c +++ b/arch/arm/mach-ux500/platsmp.c @@ -172,14 +172,11 @@ void __init smp_init_cpus(void) void __init platform_smp_prepare_cpus(unsigned int max_cpus) { - int i; - /* * Initialise the present map, which describes the set of CPUs * actually populated at the present time. */ - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); + init_cpu_present(&cpu_possible_map); scu_enable(scu_base_addr()); wakeup_secondary(); diff --git a/arch/arm/mach-vexpress/ct-ca9x4.c b/arch/arm/mach-vexpress/ct-ca9x4.c index 765a71f..c7cd438 100644 --- a/arch/arm/mach-vexpress/ct-ca9x4.c +++ b/arch/arm/mach-vexpress/ct-ca9x4.c @@ -229,10 +229,7 @@ static void ct_ca9x4_init_cpu_map(void) static void ct_ca9x4_smp_enable(unsigned int max_cpus) { - int i; - for (i = 0; i < max_cpus; i++) - set_cpu_present(i, true); - + init_cpu_present(&cpu_possible_map); scu_enable(MMIO_P2V(A9_MPCORE_SCU)); } #endif
If an ARM system has multiple cpus in the same socket and the kernel is booted with maxcpus=1, secondary cpus are possible but not present due to how platform_smp_prepare_cpus() is called. Fix this by always calling platform_smp_prepare_cpus() as long as max_cpus is non-zero (0 means no SMP) to allow platform code to decide if any non-boot cpus are present in the system. Since all current platform code doesn't support physical hotplug we have a situation where possible == present and thus we can simply copy the possible map to the present map. With this patch it's possible to boot an ARM system with maxcpus=1 on the command line and then hotplug in secondary cpus via sysfs. This is more in line with how x86 works with maxcpus=1 on the command line. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- This patch was tested along with an MSM patch: https://lkml.org/lkml/2011/4/7/354 I don't have any non-MSM hardware to test on so Acks and tested-bys are welcome. arch/arm/kernel/smp.c | 3 +-- arch/arm/mach-exynos4/platsmp.c | 5 +---- arch/arm/mach-msm/platsmp.c | 5 +---- arch/arm/mach-omap2/omap-smp.c | 5 +---- arch/arm/mach-realview/platsmp.c | 5 +---- arch/arm/mach-shmobile/platsmp.c | 5 +---- arch/arm/mach-tegra/platsmp.c | 5 +---- arch/arm/mach-ux500/platsmp.c | 5 +---- arch/arm/mach-vexpress/ct-ca9x4.c | 5 +---- 9 files changed, 9 insertions(+), 34 deletions(-)