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Filename Latest commit message Latest commit date
Juri Lelli 83bdf7f8b7 sched/core: Fix PI boosting between RT and DEADLINE tasks
[ Upstream commit 740797ce3a124b7dd22b7fb832d87bc8fba1cf6f ]

syzbot reported the following warning:

 WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628
 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504

At deadline.c:628 we have:

 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se)
 624 {
 625 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 626 	struct rq *rq = rq_of_dl_rq(dl_rq);
 627
 628 	WARN_ON(dl_se->dl_boosted);
 629 	WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline));
        [...]
     }

Which means that setup_new_dl_entity() has been called on a task
currently boosted. This shouldn't happen though, as setup_new_dl_entity()
is only called when the 'dynamic' deadline of the new entity
is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this
condition.

Digging through the PI code I noticed that what above might in fact happen
if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the
first branch of boosting conditions we check only if a pi_task 'dynamic'
deadline is earlier than mutex holder's and in this case we set mutex
holder to be dl_boosted. However, since RT 'dynamic' deadlines are only
initialized if such tasks get boosted at some point (or if they become
DEADLINE of course), in general RT 'dynamic' deadlines are usually equal
to 0 and this verifies the aforementioned condition.

Fix it by checking that the potential donor task is actually (even if
temporary because in turn boosted) running at DEADLINE priority before
using its 'dynamic' deadline value.

Fixes: 2d3d891d33 ("sched/deadline: Add SCHED_DEADLINE inheritance logic")
Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Tested-by: Daniel Wagner <dwagner@suse.de>
Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-06-30 15:37:02 -04:00
arch ARM: imx5: add missing put_device() call in imx_suspend_alloc_ocram() 2020-06-30 15:37:00 -04:00
block block/bio-integrity: don't free 'buf' if bio_integrity_add_page() failed 2020-06-30 15:36:43 -04:00
certs
crypto crypto: algboss - don't wait during notifier callback 2020-06-24 17:50:51 +02:00
Documentation dt-bindings: display: mediatek: control dpi pins mode to avoid leakage 2020-06-22 09:30:58 +02:00
drivers i2c: core: check returned size of emulated smbus block read 2020-06-30 15:37:02 -04:00
fs afs: Fix storage of cell names 2020-06-30 15:37:02 -04:00
include net: qed: fix left elements count calculation 2020-06-30 15:36:58 -04:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel sched/core: Fix PI boosting between RT and DEADLINE tasks 2020-06-30 15:37:02 -04:00
lib lib/zlib: remove outdated and incorrect pre-increment optimization 2020-06-24 17:50:39 +02:00
LICENSES
mm mm: call cond_resched() from deferred_init_memmap() 2020-06-22 09:31:14 +02:00
net netfilter: ipset: fix unaligned atomic access 2020-06-30 15:37:01 -04:00
samples bpf, xdp, samples: Fix null pointer dereference in *_user code 2020-06-30 15:36:55 -04:00
scripts scripts: headers_install: Exit with error on config leak 2020-06-24 17:50:33 +02:00
security selinux: fix double free 2020-06-24 17:50:48 +02:00
sound ASoC: rockchip: Fix a reference count leak. 2020-06-30 15:36:57 -04:00
tools selftests/net: report etf errors correctly 2020-06-30 15:36:58 -04:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Save the host's PtrAuth keys in non-preemptible context 2020-06-17 16:40:38 +02:00
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Makefile Linux 5.4.49 2020-06-24 17:50:53 +02:00
README

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.