4.4-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 32a7726c4f4aadfabdb82440d84f88a5a2c8fe13 ]
- 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 jcmvbkbc@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/xtensa/kernel/head.S | 5 ++++- arch/xtensa/kernel/smp.c | 34 +++++++++++++++++++++------------- 2 files changed, 25 insertions(+), 14 deletions(-)
diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S index c7b3bedbfffe..e3823b4f9d08 100644 --- a/arch/xtensa/kernel/head.S +++ b/arch/xtensa/kernel/head.S @@ -286,12 +286,13 @@ should_never_return:
movi a2, cpu_start_ccount 1: + memw l32i a3, a2, 0 beqi a3, 0, 1b movi a3, 0 s32i a3, a2, 0 - memw 1: + memw l32i a3, a2, 0 beqi a3, 0, 1b wsr a3, ccount @@ -328,11 +329,13 @@ ENTRY(cpu_restart) rsr a0, prid neg a2, a0 movi a3, cpu_start_id + memw s32i a2, a3, 0 #if XCHAL_DCACHE_IS_WRITEBACK dhwbi a3, 0 #endif 1: + memw l32i a2, a3, 0 dhi a3, 0 bne a2, a0, 1b diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index 4d02e38514f5..545144d1431d 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -192,9 +192,11 @@ 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);
@@ -203,18 +205,21 @@ 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; } } @@ -234,6 +239,7 @@ 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, @@ -295,8 +301,10 @@ 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; }