From: Ira Weiny <ira.weiny@intel.com>
To: Tomas Glozar <tglozar@redhat.com>, <nvdimm@lists.linux.dev>
Cc: <dan.j.williams@intel.com>, <vishal.l.verma@intel.com>,
<dave.jiang@intel.com>, <ira.weiny@intel.com>,
<linux-kernel@vger.kernel.org>, Tomas Glozar <tglozar@redhat.com>
Subject: Re: [PATCH v2] nd_btt: Make BTT lanes preemptible
Date: Mon, 25 Sep 2023 09:10:11 -0700 [thread overview]
Message-ID: <6511b0e3a4627_b00c32947a@iweiny-mobl.notmuch> (raw)
In-Reply-To: <20230920053712.499439-1-tglozar@redhat.com>
Tomas Glozar wrote:
> nd_region_acquire_lane uses get_cpu, which disables preemption. This is
> an issue on PREEMPT_RT kernels, since btt_write_pg and also
> nd_region_acquire_lane itself take a spin lock, resulting in BUG:
> sleeping function called from invalid context.
>
> Fix the issue by replacing get_cpu with smp_process_id and
> migrate_disable when needed. This makes BTT operations preemptible, thus
> permitting the use of spin_lock.
>
> BUG example occurring when running ndctl tests on PREEMPT_RT kernel:
>
> BUG: sleeping function called from invalid context at
> kernel/locking/spinlock_rt.c:48
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 4903, name:
> libndctl
> preempt_count: 1, expected: 0
> RCU nest depth: 0, expected: 0
> Preemption disabled at:
> [<ffffffffc1313db5>] nd_region_acquire_lane+0x15/0x90 [libnvdimm]
> Call Trace:
> <TASK>
> dump_stack_lvl+0x8e/0xb0
> __might_resched+0x19b/0x250
> rt_spin_lock+0x4c/0x100
> ? btt_write_pg+0x2d7/0x500 [nd_btt]
> btt_write_pg+0x2d7/0x500 [nd_btt]
> ? local_clock_noinstr+0x9/0xc0
> btt_submit_bio+0x16d/0x270 [nd_btt]
> __submit_bio+0x48/0x80
> __submit_bio_noacct+0x7e/0x1e0
> submit_bio_wait+0x58/0xb0
> __blkdev_direct_IO_simple+0x107/0x240
> ? inode_set_ctime_current+0x51/0x110
> ? __pfx_submit_bio_wait_endio+0x10/0x10
> blkdev_write_iter+0x1d8/0x290
> vfs_write+0x237/0x330
> ...
> </TASK>
>
> Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
> Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Thanks for the clarification.
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
prev parent reply other threads:[~2023-09-25 16:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-20 5:37 [PATCH v2] nd_btt: Make BTT lanes preemptible Tomas Glozar
2023-09-22 22:22 ` Verma, Vishal L
2023-09-25 16:10 ` Ira Weiny [this message]
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