d455f29f6d
Fix possible recursive lock warning. Its a false warning as the locks are part of two differnt HW Queue data structure - cmdq and creq. Debug kernel is throwing the following warning and stack trace. [ 783.914967] ============================================ [ 783.914970] WARNING: possible recursive locking detected [ 783.914973] 4.19.0-rc2+ #33 Not tainted [ 783.914976] -------------------------------------------- [ 783.914979] swapper/2/0 is trying to acquire lock: [ 783.914982] 000000002aa3949d (&(&hwq->lock)->rlock){..-.}, at: bnxt_qplib_service_creq+0x232/0x350 [bnxt_re] [ 783.914999] but task is already holding lock: [ 783.915002] 00000000be73920d (&(&hwq->lock)->rlock){..-.}, at: bnxt_qplib_service_creq+0x2a/0x350 [bnxt_re] [ 783.915013] other info that might help us debug this: [ 783.915016] Possible unsafe locking scenario: [ 783.915019] CPU0 [ 783.915021] ---- [ 783.915034] lock(&(&hwq->lock)->rlock); [ 783.915035] lock(&(&hwq->lock)->rlock); [ 783.915037] *** DEADLOCK *** [ 783.915038] May be due to missing lock nesting notation [ 783.915039] 1 lock held by swapper/2/0: [ 783.915040] #0: 00000000be73920d (&(&hwq->lock)->rlock){..-.}, at: bnxt_qplib_service_creq+0x2a/0x350 [bnxt_re] [ 783.915044] stack backtrace: [ 783.915046] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.19.0-rc2+ #33 [ 783.915047] Hardware name: Dell Inc. PowerEdge R730/0599V5, BIOS 1.0.4 08/28/2014 [ 783.915048] Call Trace: [ 783.915049] <IRQ> [ 783.915054] dump_stack+0x90/0xe3 [ 783.915058] __lock_acquire+0x106c/0x1080 [ 783.915061] ? sched_clock+0x5/0x10 [ 783.915063] lock_acquire+0xbd/0x1a0 [ 783.915065] ? bnxt_qplib_service_creq+0x232/0x350 [bnxt_re] [ 783.915069] _raw_spin_lock_irqsave+0x4a/0x90 [ 783.915071] ? bnxt_qplib_service_creq+0x232/0x350 [bnxt_re] [ 783.915073] bnxt_qplib_service_creq+0x232/0x350 [bnxt_re] [ 783.915078] tasklet_action_common.isra.17+0x197/0x1b0 [ 783.915081] __do_softirq+0xcb/0x3a6 [ 783.915084] irq_exit+0xe9/0x100 [ 783.915085] do_IRQ+0x6a/0x120 [ 783.915087] common_interrupt+0xf/0xf [ 783.915088] </IRQ> Use nested notation for the spin_lock to avoid this warning. Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.