d8fd372220
Fix the breakage resulting in the stacktrace below, due to tx queue being full when trying to send an up-reply. txmsg->seqno is -1 in this case leading to a corruption of the mstb object by txmsg->dst->tx_slots[txmsg->seqno] = NULL; in process_single_up_tx_qlock(). [ +0,005162] [drm:process_single_tx_qlock [drm_kms_helper]] set_hdr_from_dst_qlock: failed to find slot [ +0,000015] [drm:drm_dp_send_up_ack_reply.constprop.19 [drm_kms_helper]] failed to send msg in q -11 [ +0,000939] BUG: kernel NULL pointer dereference, address: 00000000000005a0 [ +0,006982] #PF: supervisor write access in kernel mode [ +0,005223] #PF: error_code(0x0002) - not-present page [ +0,005135] PGD 0 P4D 0 [ +0,002581] Oops: 0002 [#1] PREEMPT SMP NOPTI [ +0,004359] CPU: 1 PID: 1200 Comm: kworker/u16:3 Tainted: G U 5.2.0-rc1+ #410 [ +0,008433] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP, BIOS ICLSFWR1.R00.3175.A00.1904261428 04/26/2019 [ +0,013323] Workqueue: i915-dp i915_digport_work_func [i915] [ +0,005676] RIP: 0010:queue_work_on+0x19/0x70 [ +0,004372] Code: ff ff ff 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 41 56 49 89 f6 41 55 41 89 fd 41 54 55 53 48 89 d3 9c 5d fa e8 e7 81 0c 00 <f0> 48 0f ba 2b 00 73 31 45 31 e4 f7 c5 00 02 00 00 74 13 e8 cf 7f [ +0,018750] RSP: 0018:ffffc900007dfc50 EFLAGS: 00010006 [ +0,005222] RAX: 0000000000000046 RBX: 00000000000005a0 RCX: 0000000000000001 [ +0,007133] RDX: 000000000001b608 RSI: 0000000000000000 RDI: ffffffff82121972 [ +0,007129] RBP: 0000000000000202 R08: 0000000000000000 R09: 0000000000000001 [ +0,007129] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88847bfa5096 [ +0,007131] R13: 0000000000000010 R14: ffff88849c08f3f8 R15: 0000000000000000 [ +0,007128] FS: 0000000000000000(0000) GS:ffff88849dc80000(0000) knlGS:0000000000000000 [ +0,008083] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ +0,005749] CR2: 00000000000005a0 CR3: 0000000005210006 CR4: 0000000000760ee0 [ +0,007128] PKRU: 55555554 [ +0,002722] Call Trace: [ +0,002458] drm_dp_mst_handle_up_req+0x517/0x540 [drm_kms_helper] [ +0,006197] ? drm_dp_mst_hpd_irq+0x5b/0x9c0 [drm_kms_helper] [ +0,005764] drm_dp_mst_hpd_irq+0x5b/0x9c0 [drm_kms_helper] [ +0,005623] ? intel_dp_hpd_pulse+0x205/0x370 [i915] [ +0,005018] intel_dp_hpd_pulse+0x205/0x370 [i915] [ +0,004836] i915_digport_work_func+0xbb/0x140 [i915] [ +0,005108] process_one_work+0x245/0x610 [ +0,004027] worker_thread+0x37/0x380 [ +0,003684] ? process_one_work+0x610/0x610 [ +0,004184] kthread+0x119/0x130 [ +0,003240] ? kthread_park+0x80/0x80 [ +0,003668] ret_from_fork+0x24/0x50 Cc: Lyude Paul <lyude@redhat.com> Cc: Dave Airlie <airlied@redhat.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Reviewed-by: Lyude Paul <lyude@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190523212433.9058-1-imre.deak@intel.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.
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.