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.f...@cn.fujitsu.com>
Cc: Stable <sta...@vger.kernel.org>
---
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
--
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