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Message-ID: <198c4edf-045c-8d85-1d5c-018378eeb490@roeck-us.net>
Date: Thu, 20 Jul 2023 07:26:54 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Mark Brown <broonie@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
linux-kernel@...r.kernel.org
Subject: Re: Traceback with CONFIG_REGMAP_KUNIT=y+CONFIG_DEBUG_ATOMIC_SLEEP=y
On 7/20/23 01:50, Dan Carpenter wrote:
> On Wed, Jul 19, 2023 at 03:37:54PM -0700, Guenter Roeck wrote:
>> Hi,
>>
>> when booting images with both CONFIG_REGMAP_KUNIT and
>> CONFIG_DEBUG_ATOMIC_SLEEP enabled, I get the following backtrace.
>>
>> [ 4.994957] # Subtest: regmap
>> [ 4.995067] 1..14
>> [ 4.995190] KTAP version 1
>> [ 4.995308] # Subtest: basic_read_write
>> [ 4.999402] ok 1 none
>> [ 5.003028] ok 2 flat
>> [ 5.005510] BUG: sleeping function called from invalid context at include/linux/sched/mm.h:306
>> [ 5.005960] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 117, name: kunit_try_catch
>> [ 5.006219] preempt_count: 1, expected: 0
>> [ 5.006414] 1 lock held by kunit_try_catch/117:
>> [ 5.006590] #0: 833b9010 (regmap_kunit:86:(config)->lock){....}-{2:2}, at: regmap_lock_spinlock+0x14/0x1c
>> [ 5.007493] irq event stamp: 162
>> [ 5.007627] hardirqs last enabled at (161): [<80786738>] crng_make_state+0x1a0/0x294
>> [ 5.007871] hardirqs last disabled at (162): [<80c531ec>] _raw_spin_lock_irqsave+0x7c/0x80
>> [ 5.008119] softirqs last enabled at (0): [<801110ac>] copy_process+0x810/0x2138
>> [ 5.008356] softirqs last disabled at (0): [<00000000>] 0x0
>> [ 5.008688] CPU: 0 PID: 117 Comm: kunit_try_catch Tainted: G N 6.4.4-rc3-g0e8d2fdfb188 #1
>> [ 5.009011] Hardware name: Generic DT based system
>> [ 5.009277] unwind_backtrace from show_stack+0x18/0x1c
>> [ 5.009497] show_stack from dump_stack_lvl+0x38/0x5c
>> [ 5.009676] dump_stack_lvl from __might_resched+0x188/0x2d0
>> [ 5.009860] __might_resched from __kmem_cache_alloc_node+0x1dc/0x25c
>> [ 5.010061] __kmem_cache_alloc_node from kmalloc_trace+0x30/0xc8
>> [ 5.010254] kmalloc_trace from regcache_rbtree_write+0x26c/0x468
>> [ 5.010446] regcache_rbtree_write from _regmap_write+0x88/0x140
>> [ 5.010634] _regmap_write from regmap_write+0x44/0x68
>> [ 5.010803] regmap_write from basic_read_write+0x8c/0x270
>> [ 5.010980] basic_read_write from kunit_try_run_case+0x48/0xa0
>> [ 5.011170] kunit_try_run_case from kunit_generic_run_threadfn_adapter+0x1c/0x28
>> [ 5.011396] kunit_generic_run_threadfn_adapter from kthread+0xf8/0x120
>> [ 5.011603] kthread from ret_from_fork+0x14/0x3c
>> [ 5.011801] Exception stack(0x881a5fb0 to 0x881a5ff8)
>> [ 5.012024] 5fa0: 00000000 00000000 00000000 00000000
>> [ 5.012269] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>> [ 5.012502] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
>> [ 5.014546] ok 3 rbtree
>> [ 5.018988] ok 4 maple
>>
>> This isn't surprising given that the regmap code allocates rbcache nodes
>> with GFP_KERNEL and the regmap configuration results in using spinlock
>> to lock regmap accesses.
>>
>> I'll be happy to submit a patch to fix the problem, but I would need
>> some advice. I could
>>
>> - Update the unit test regmap configuration to avoid using
>> spinlock as locking mechanism for rbtree tests.
>> That would work, but fail to catch situations where this happens
>> in the real world.
>> - Use a different method to allocate memory in regcache_rbtree_node_alloc().
>> - Replace GFP_KERNEL with GFP_NOWAIT or GFP_KERNEL | __GFP_NOWARN (?)
>> or something else, possibly only if gfpflags_allow_blocking() is false
>
> __GFP_NOWARN is only about allocation failure, not sleeping. I would
> have thought it should be.
>
> diff --git a/drivers/base/regmap/regcache-rbtree.c b/drivers/base/regmap/regcache-rbtree.c
> index fabf87058d80..d94e25120f2f 100644
> --- a/drivers/base/regmap/regcache-rbtree.c
> +++ b/drivers/base/regmap/regcache-rbtree.c
> @@ -187,7 +187,7 @@ static int regcache_rbtree_init(struct regmap *map)
> int i;
> int ret;
>
> - map->cache = kmalloc(sizeof *rbtree_ctx, GFP_KERNEL);
> + map->cache = kmalloc(sizeof *rbtree_ctx, map->alloc_flags);
Yes, that might work as well (and after looking more deeply into the code
I wondered why it wasn't used in the first place).
Based on Mark's feedback I submitted
https://lore.kernel.org/lkml/20230720032848.1306349-1-linux@roeck-us.net/
Sorry, I forgot to copy you on that one.
Mark, please let me know what you prefer.
Thanks,
Guenter
> if (!map->cache)
> return -ENOMEM;
>
> @@ -277,7 +277,7 @@ static int regcache_rbtree_insert_to_block(struct regmap *map,
>
> blk = krealloc(rbnode->block,
> blklen * map->cache_word_size,
> - GFP_KERNEL);
> + map->alloc_flags);
> if (!blk)
> return -ENOMEM;
>
> @@ -286,7 +286,7 @@ static int regcache_rbtree_insert_to_block(struct regmap *map,
> if (BITS_TO_LONGS(blklen) > BITS_TO_LONGS(rbnode->blklen)) {
> present = krealloc(rbnode->cache_present,
> BITS_TO_LONGS(blklen) * sizeof(*present),
> - GFP_KERNEL);
> + map->alloc_flags);
> if (!present)
> return -ENOMEM;
>
> @@ -320,7 +320,7 @@ regcache_rbtree_node_alloc(struct regmap *map, unsigned int reg)
> const struct regmap_range *range;
> int i;
>
> - rbnode = kzalloc(sizeof(*rbnode), GFP_KERNEL);
> + rbnode = kzalloc(sizeof(*rbnode), map->alloc_flags);
> if (!rbnode)
> return NULL;
>
> @@ -346,13 +346,13 @@ regcache_rbtree_node_alloc(struct regmap *map, unsigned int reg)
> }
>
> rbnode->block = kmalloc_array(rbnode->blklen, map->cache_word_size,
> - GFP_KERNEL);
> + map->alloc_flags);
> if (!rbnode->block)
> goto err_free;
>
> rbnode->cache_present = kcalloc(BITS_TO_LONGS(rbnode->blklen),
> sizeof(*rbnode->cache_present),
> - GFP_KERNEL);
> + map->alloc_flags);
> if (!rbnode->cache_present)
> goto err_free_block;
>
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