From 32a7726c4f4aadfabdb82440d84f88a5a2c8fe13 Mon Sep 17 00:00:00 2001 From: Max Filippov Date: Fri, 21 Dec 2018 08:26:20 -0800 Subject: xtensa: SMP: fix secondary CPU initialization - add missing memory barriers to the secondary CPU synchronization spin loops; add comment to the matching memory barrier in the boot_secondary and __cpu_die functions; - use READ_ONCE/WRITE_ONCE to access cpu_start_id/cpu_start_ccount instead of reading/writing them directly; - re-initialize cpu_running every time before starting secondary CPU to flush possible previous CPU startup results. Signed-off-by: Max Filippov --- arch/xtensa/kernel/smp.c | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) (limited to 'arch/xtensa/kernel/smp.c') diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index 932d64689bac..c9fc2c4f71b3 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -195,9 +195,11 @@ static int boot_secondary(unsigned int cpu, struct task_struct *ts) int i; #ifdef CONFIG_HOTPLUG_CPU - cpu_start_id = cpu; - system_flush_invalidate_dcache_range( - (unsigned long)&cpu_start_id, sizeof(cpu_start_id)); + WRITE_ONCE(cpu_start_id, cpu); + /* Pairs with the third memw in the cpu_restart */ + mb(); + system_flush_invalidate_dcache_range((unsigned long)&cpu_start_id, + sizeof(cpu_start_id)); #endif smp_call_function_single(0, mx_cpu_start, (void *)cpu, 1); @@ -206,18 +208,21 @@ static int boot_secondary(unsigned int cpu, struct task_struct *ts) ccount = get_ccount(); while (!ccount); - cpu_start_ccount = ccount; + WRITE_ONCE(cpu_start_ccount, ccount); - while (time_before(jiffies, timeout)) { + do { + /* + * Pairs with the first two memws in the + * .Lboot_secondary. + */ mb(); - if (!cpu_start_ccount) - break; - } + ccount = READ_ONCE(cpu_start_ccount); + } while (ccount && time_before(jiffies, timeout)); - if (cpu_start_ccount) { + if (ccount) { smp_call_function_single(0, mx_cpu_stop, - (void *)cpu, 1); - cpu_start_ccount = 0; + (void *)cpu, 1); + WRITE_ONCE(cpu_start_ccount, 0); return -EIO; } } @@ -237,6 +242,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) pr_debug("%s: Calling wakeup_secondary(cpu:%d, idle:%p, sp: %08lx)\n", __func__, cpu, idle, start_info.stack); + init_completion(&cpu_running); ret = boot_secondary(cpu, idle); if (ret == 0) { wait_for_completion_timeout(&cpu_running, @@ -298,8 +304,10 @@ void __cpu_die(unsigned int cpu) unsigned long timeout = jiffies + msecs_to_jiffies(1000); while (time_before(jiffies, timeout)) { system_invalidate_dcache_range((unsigned long)&cpu_start_id, - sizeof(cpu_start_id)); - if (cpu_start_id == -cpu) { + sizeof(cpu_start_id)); + /* Pairs with the second memw in the cpu_restart */ + mb(); + if (READ_ONCE(cpu_start_id) == -cpu) { platform_cpu_kill(cpu); return; } -- cgit v1.2.1 From 8b1c42cdd7181200dc1fff39dcb6ac1a3fac2c25 Mon Sep 17 00:00:00 2001 From: Max Filippov Date: Sat, 19 Jan 2019 00:26:48 -0800 Subject: xtensa: SMP: mark each possible CPU as present Otherwise it is impossible to enable CPUs after booting with 'maxcpus' parameter. Signed-off-by: Max Filippov --- arch/xtensa/kernel/smp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/xtensa/kernel/smp.c') diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index c9fc2c4f71b3..80be6449c497 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -83,7 +83,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus) { unsigned i; - for (i = 0; i < max_cpus; ++i) + for_each_possible_cpu(i) set_cpu_present(i, true); } -- cgit v1.2.1 From 25384ce5f9530def39421597b1457d9462df6455 Mon Sep 17 00:00:00 2001 From: Max Filippov Date: Sat, 26 Jan 2019 20:35:18 -0800 Subject: xtensa: SMP: limit number of possible CPUs by NR_CPUS This fixes the following warning at boot when the kernel is booted on a board with more CPU cores than was configured in NR_CPUS: smp_init_cpus: Core Count = 8 smp_init_cpus: Core Id = 0 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at include/linux/cpumask.h:121 smp_init_cpus+0x54/0x74 Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc3-00015-g1459333f88a0 #124 Call Trace: __warn$part$3+0x6a/0x7c warn_slowpath_null+0x35/0x3c smp_init_cpus+0x54/0x74 setup_arch+0x1c0/0x1d0 start_kernel+0x44/0x310 _startup+0x107/0x107 Signed-off-by: Max Filippov --- arch/xtensa/kernel/smp.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'arch/xtensa/kernel/smp.c') diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index 80be6449c497..be1f280c322c 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -96,6 +96,11 @@ void __init smp_init_cpus(void) pr_info("%s: Core Count = %d\n", __func__, ncpus); pr_info("%s: Core Id = %d\n", __func__, core_id); + if (ncpus > NR_CPUS) { + ncpus = NR_CPUS; + pr_info("%s: limiting core count by %d\n", __func__, ncpus); + } + for (i = 0; i < ncpus; ++i) set_cpu_possible(i, true); } -- cgit v1.2.1