The following lockdep warning occurrs when running with latest kernel: [ 3.178000] ------------[ cut here ]------------ [ 3.183000] WARNING: CPU: 128 PID: 0 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0xdd/0xe0() [ 3.193000] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)) [ 3.199000] Modules linked in: [ 3.203000] CPU: 128 PID: 0 Comm: swapper/128 Not tainted 4.1.0-rc3 #70 [ 3.221000] 0000000000000000 2d6601fb3e6d4e4c ffff88086fd5fc38 ffffffff81773f0a [ 3.230000] 0000000000000000 ffff88086fd5fc90 ffff88086fd5fc78 ffffffff8108c85a [ 3.238000] ffff88086fd60000 0000000000000092 ffff88086fd60000 00000000000000d0 [ 3.246000] Call Trace: [ 3.249000] [<ffffffff81773f0a>] dump_stack+0x4c/0x65 [ 3.255000] [<ffffffff8108c85a>] warn_slowpath_common+0x8a/0xc0 [ 3.261000] [<ffffffff8108c8e5>] warn_slowpath_fmt+0x55/0x70 [ 3.268000] [<ffffffff810ee24d>] lockdep_trace_alloc+0xdd/0xe0 [ 3.274000] [<ffffffff811cda0d>] __alloc_pages_nodemask+0xad/0xca0 [ 3.281000] [<ffffffff810ec7ad>] ? __lock_acquire+0xf6d/0x1560 [ 3.288000] [<ffffffff81219c8a>] alloc_page_interleave+0x3a/0x90 [ 3.295000] [<ffffffff8121b32d>] alloc_pages_current+0x17d/0x1a0 [ 3.301000] [<ffffffff811c869e>] ? __get_free_pages+0xe/0x50 [ 3.308000] [<ffffffff811c869e>] __get_free_pages+0xe/0x50 [ 3.314000] [<ffffffff8102640b>] init_espfix_ap+0x17b/0x320 [ 3.320000] [<ffffffff8105c691>] start_secondary+0xf1/0x1f0 [ 3.327000] ---[ end trace 1b3327d9d6a1d62c ]--- This seems a mis-warning by lockdep, as we alloc pages with GFP_KERNEL in init_espfix_ap() which is called before enabled local irq, and the lockdep sub-system considers this behaviour as allocating memory with GFP_FS with local irq disabled, then trigger the warning as mentioned about. Though here we use GFP_NOFS rather GFP_KERNEL to avoid the warning, but you know, init_espfix_ap is called with preempt and local irq disabled, it is not a good idea to use mutex (might sleep) here. So we convert the initialization lock to spin_lock here to avoid the noise. Signed-off-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx> Cc: Stable <stable@xxxxxxxxxxxxxxx> --- arch/x86/kernel/espfix_64.c | 13 +++++++------ 1 files changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c index f5d0730..ceb35a3 100644 --- a/arch/x86/kernel/espfix_64.c +++ b/arch/x86/kernel/espfix_64.c @@ -57,14 +57,14 @@ # error "Need more than one PGD for the ESPFIX hack" #endif -#define PGALLOC_GFP (GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO) +#define PGALLOC_GFP (GFP_ATOMIC | __GFP_NOTRACK | __GFP_ZERO) /* This contains the *bottom* address of the espfix stack */ DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_stack); DEFINE_PER_CPU_READ_MOSTLY(unsigned long, espfix_waddr); -/* Initialization mutex - should this be a spinlock? */ -static DEFINE_MUTEX(espfix_init_mutex); +/* Initialization lock */ +static DEFINE_SPINLOCK(espfix_init_lock); /* Page allocation bitmap - each page serves ESPFIX_STACKS_PER_PAGE CPUs */ #define ESPFIX_MAX_PAGES DIV_ROUND_UP(CONFIG_NR_CPUS, ESPFIX_STACKS_PER_PAGE) @@ -144,6 +144,7 @@ void init_espfix_ap(void) int n; void *stack_page; pteval_t ptemask; + unsigned long flags; /* We only have to do this once... */ if (likely(this_cpu_read(espfix_stack))) @@ -158,7 +159,7 @@ void init_espfix_ap(void) if (likely(stack_page)) goto done; - mutex_lock(&espfix_init_mutex); + spin_lock_irqsave(&espfix_init_lock, flags); /* Did we race on the lock? */ stack_page = ACCESS_ONCE(espfix_pages[page]); @@ -188,7 +189,7 @@ void init_espfix_ap(void) } pte_p = pte_offset_kernel(&pmd, addr); - stack_page = (void *)__get_free_page(GFP_KERNEL); + stack_page = (void *)__get_free_page(PGALLOC_GFP); pte = __pte(__pa(stack_page) | (__PAGE_KERNEL_RO & ptemask)); for (n = 0; n < ESPFIX_PTE_CLONES; n++) set_pte(&pte_p[n*PTE_STRIDE], pte); @@ -197,7 +198,7 @@ void init_espfix_ap(void) ACCESS_ONCE(espfix_pages[page]) = stack_page; unlock_done: - mutex_unlock(&espfix_init_mutex); + spin_unlock_irqrestore(&espfix_init_lock, flags); done: this_cpu_write(espfix_stack, addr); this_cpu_write(espfix_waddr, (unsigned long)stack_page -- 1.7.7 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html