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Subject[PATCH] mm: Fix memory_dev_init() long delay
Date
One system with 2048g ram, reported soft lockup on recent kernel.

[ 34.426749] cpu_dev_init done
[ 61.166399] BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]
[ 61.166733] Modules linked in:
[ 61.166904] irq event stamp: 1935610
[ 61.178431] hardirqs last enabled at (1935609): [<ffffffff81ce8c05>] mutex_lock_nested+0x299/0x2b4
[ 61.178923] hardirqs last disabled at (1935610): [<ffffffff81cf2bab>] apic_timer_interrupt+0x6b/0x80
[ 61.198767] softirqs last enabled at (1935476): [<ffffffff8106e59c>] __do_softirq+0x195/0x1ab
[ 61.218604] softirqs last disabled at (1935471): [<ffffffff81cf359c>] call_softirq+0x1c/0x30
[ 61.238408] CPU 0
[ 61.238549] Modules linked in:
[ 61.238744]
[ 61.238825] Pid: 1, comm: swapper/0 Not tainted 3.3.0-rc1-tip-yh-02076-g962f689-dirty #171
[ 61.278212] RIP: 0010:[<ffffffff810b3e3a>] [<ffffffff810b3e3a>] lock_release+0x90/0x9c
[ 61.278627] RSP: 0018:ffff883f64dbfd70 EFLAGS: 00000246
[ 61.298287] RAX: ffff883f64dc0000 RBX: 0000000000000000 RCX: 000000000000008b
[ 61.298690] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[ 61.318383] RBP: ffff883f64dbfda0 R08: 0000000000000001 R09: 000000000000008b
[ 61.338215] R10: 0000000000000000 R11: 0000000000000000 R12: ffff883f64dbfd10
[ 61.338610] R13: ffff883f64dc0708 R14: ffff883f64dc0708 R15: ffffffff81095657
[ 61.358299] FS: 0000000000000000(0000) GS:ffff883f7d600000(0000) knlGS:0000000000000000
[ 61.378118] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 61.378450] CR2: 0000000000000000 CR3: 00000000024af000 CR4: 00000000000007f0
[ 61.398144] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 61.417918] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 61.418260] Process swapper/0 (pid: 1, threadinfo ffff883f64dbe000, task ffff883f64dc0000)
[ 61.445358] Stack:
[ 61.445511] 0000000000000002 ffff897f649ba168 ffff883f64dbfe10 ffff88ff64bb57a8
[ 61.458040] 0000000000000000 0000000000000000 ffff883f64dbfdc0 ffffffff81ceb1b4
[ 61.458491] 000000000011608c ffff88ff64bb58a8 ffff883f64dbfdf0 ffffffff81c57638
[ 61.478215] Call Trace:
[ 61.478367] [<ffffffff81ceb1b4>] _raw_spin_unlock+0x21/0x2e
[ 61.497994] [<ffffffff81c57638>] klist_next+0x9e/0xbc
[ 61.498264] [<ffffffff8148ba99>] next_device+0xe/0x1e
[ 61.517867] [<ffffffff8148c0cc>] subsys_find_device_by_id+0xb7/0xd6
[ 61.518197] [<ffffffff81498846>] find_memory_block_hinted+0x3d/0x66
[ 61.537927] [<ffffffff8149887f>] find_memory_block+0x10/0x12
[ 61.538193] [<ffffffff814988b6>] add_memory_section+0x35/0x9e
[ 61.557932] [<ffffffff827fecef>] memory_dev_init+0x68/0xda
[ 61.558227] [<ffffffff827fec01>] driver_init+0x97/0xa7
[ 61.577853] [<ffffffff827cdf3c>] kernel_init+0xf6/0x1c0
[ 61.578140] [<ffffffff81cf34a4>] kernel_thread_helper+0x4/0x10
[ 61.597850] [<ffffffff81ceb59d>] ? retint_restore_args+0xe/0xe
[ 61.598144] [<ffffffff827cde46>] ? start_kernel+0x3ab/0x3ab
[ 61.617826] [<ffffffff81cf34a0>] ? gs_change+0xb/0xb
[ 61.618060] Code: 10 48 83 3b 00 eb e8 4c 89 f2 44 89 fe 4c 89 ef e8 e1 fe ff ff 65 48 8b 04 25 40 bc 00 00 c7 80 cc 06 00 00 00 00 00 00 41 54 9d <5e> 5b 41 5c 41 5d 41 5e 41 5f 5d c3 55 48 89 e5 41 57 41 89 cf
[ 89.285380] memory_dev_init done
Found we should find the memory_block for BOOT path.

Root cause: for x86_64, 2048g (with 2g hole at [2g,4g), and TOP2 will be 2050g), will have 16400 memory block.

find_memory_block/subsys_find_device_by_id will be expensive with that much entries.

Actually, we don't need to find that memory block for BOOT case.

Skip that make it get back to normal.

[ 34.466696] cpu_dev_init done
[ 35.290080] memory_dev_init done

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Cc: Nathan Fontenot <nfont@austin.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>

---
drivers/base/memory.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
Index: linux-2.6/drivers/base/memory.c
===================================================================
--- linux-2.6.orig/drivers/base/memory.c
+++ linux-2.6/drivers/base/memory.c
@@ -574,12 +574,15 @@ static int init_memory_block(struct memo
static int add_memory_section(int nid, struct mem_section *section,
unsigned long state, enum mem_add_context context)
{
- struct memory_block *mem;
+ struct memory_block *mem = NULL;
int ret = 0;

mutex_lock(&mem_sysfs_mutex);

- mem = find_memory_block(section);
+ /* don't need to find memory block for BOOT */
+ if (context != BOOT)
+ mem = find_memory_block(section);
+
if (mem) {
mem->section_count++;
kobject_put(&mem->dev.kobj);

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