<feed xmlns='http://www.w3.org/2005/Atom'>
<title>BMC/Intel-BMC/linux.git/arch, branch v4.17.7</title>
<subtitle>Intel OpenBMC Linux kernel source tree (mirror)</subtitle>
<id>https://git.radix-linux.su/BMC/Intel-BMC/linux.git/atom?h=v4.17.7</id>
<link rel='self' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/atom?h=v4.17.7'/>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/'/>
<updated>2018-07-17T09:48:36+00:00</updated>
<entry>
<title>ARM: dts: armada-38x: use the new thermal binding</title>
<updated>2018-07-17T09:48:36+00:00</updated>
<author>
<name>Baruch Siach</name>
<email>baruch@tkos.co.il</email>
</author>
<published>2018-07-03T03:24:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=8d930a6f0a281a8012f6430aba62f81a0ddaaf56'/>
<id>urn:sha1:8d930a6f0a281a8012f6430aba62f81a0ddaaf56</id>
<content type='text'>
commit 568cc2f07c8ea5f71a0486464bd9703e4671045f upstream.

Commit 2f28e4c24b10e (thermal: armada: Clarify control registers
accesses) introduced the new thermal binding. The new binding extends
the second registers field size to 8. Switch to the new binding to fix
thermal reading values. Without this change the fix for errata #132698
introduced in commit 8c0b888f661 (thermal: armada: Change sensors trim
default value) has no effect.

Cc: stable@vger.kernel.org # v4.16+
Reviewed-by: Miquel Raynal &lt;miquel.raynal@bootlin.com&gt;
Signed-off-by: Baruch Siach &lt;baruch@tkos.co.il&gt;
Signed-off-by: Gregory CLEMENT &lt;gregory.clement@bootlin.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>kvm: vmx: Nested VM-entry prereqs for event inj.</title>
<updated>2018-07-17T09:48:34+00:00</updated>
<author>
<name>Marc Orr</name>
<email>marcorr@google.com</email>
</author>
<published>2018-06-21T00:21:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=65e044949dae058da0fe5373d8ff5ed3087e93dc'/>
<id>urn:sha1:65e044949dae058da0fe5373d8ff5ed3087e93dc</id>
<content type='text'>
commit 0447378a4a793da008451fad50bc0f93e9675ae6 upstream.

This patch extends the checks done prior to a nested VM entry.
Specifically, it extends the check_vmentry_prereqs function with checks
for fields relevant to the VM-entry event injection information, as
described in the Intel SDM, volume 3.

This patch is motivated by a syzkaller bug, where a bad VM-entry
interruption information field is generated in the VMCS02, which causes
the nested VM launch to fail. Then, KVM fails to resume L1.

While KVM should be improved to correctly resume L1 execution after a
failed nested launch, this change is justified because the existing code
to resume L1 is flaky/ad-hoc and the test coverage for resuming L1 is
sparse.

Reported-by: syzbot &lt;syzkaller@googlegroups.com&gt;
Signed-off-by: Marc Orr &lt;marcorr@google.com&gt;
[Removed comment whose parts were describing previous revisions and the
 rest was obvious from function/variable naming. - Radim]
Signed-off-by: Radim Krčmář &lt;rkrcmar@redhat.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>uprobes/x86: Remove incorrect WARN_ON() in uprobe_init_insn()</title>
<updated>2018-07-17T09:48:33+00:00</updated>
<author>
<name>Oleg Nesterov</name>
<email>oleg@redhat.com</email>
</author>
<published>2018-05-18T16:27:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=95262c792d3782659184648794a184d25801a26a'/>
<id>urn:sha1:95262c792d3782659184648794a184d25801a26a</id>
<content type='text'>
commit 90718e32e1dcc2479acfa208ccfc6442850b594c upstream.

insn_get_length() has the side-effect of processing the entire instruction
but only if it was decoded successfully, otherwise insn_complete() can fail
and in this case we need to just return an error without warning.

Reported-by: syzbot+30d675e3ca03c1c351e7@syzkaller.appspotmail.com
Signed-off-by: Oleg Nesterov &lt;oleg@redhat.com&gt;
Reviewed-by: Masami Hiramatsu &lt;mhiramat@kernel.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: syzkaller-bugs@googlegroups.com
Link: https://lkml.kernel.org/lkml/20180518162739.GA5559@redhat.com
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>crypto: x86/salsa20 - remove x86 salsa20 implementations</title>
<updated>2018-07-17T09:48:32+00:00</updated>
<author>
<name>Eric Biggers</name>
<email>ebiggers@google.com</email>
</author>
<published>2018-05-26T07:08:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=49c8ef6d52ed6dacbca5a731ebe253bfb44e0ea9'/>
<id>urn:sha1:49c8ef6d52ed6dacbca5a731ebe253bfb44e0ea9</id>
<content type='text'>
commit b7b73cd5d74694ed59abcdb4974dacb4ff8b2a2a upstream.

The x86 assembly implementations of Salsa20 use the frame base pointer
register (%ebp or %rbp), which breaks frame pointer convention and
breaks stack traces when unwinding from an interrupt in the crypto code.
Recent (v4.10+) kernels will warn about this, e.g.

WARNING: kernel stack regs at 00000000a8291e69 in syzkaller047086:4677 has bad 'bp' value 000000001077994c
[...]

But after looking into it, I believe there's very little reason to still
retain the x86 Salsa20 code.  First, these are *not* vectorized
(SSE2/SSSE3/AVX2) implementations, which would be needed to get anywhere
close to the best Salsa20 performance on any remotely modern x86
processor; they're just regular x86 assembly.  Second, it's still
unclear that anyone is actually using the kernel's Salsa20 at all,
especially given that now ChaCha20 is supported too, and with much more
efficient SSSE3 and AVX2 implementations.  Finally, in benchmarks I did
on both Intel and AMD processors with both gcc 8.1.0 and gcc 4.9.4, the
x86_64 salsa20-asm is actually slightly *slower* than salsa20-generic
(~3% slower on Skylake, ~10% slower on Zen), while the i686 salsa20-asm
is only slightly faster than salsa20-generic (~15% faster on Skylake,
~20% faster on Zen).  The gcc version made little difference.

So, the x86_64 salsa20-asm is pretty clearly useless.  That leaves just
the i686 salsa20-asm, which based on my tests provides a 15-20% speed
boost.  But that's without updating the code to not use %ebp.  And given
the maintenance cost, the small speed difference vs. salsa20-generic,
the fact that few people still use i686 kernels, the doubt that anyone
is even using the kernel's Salsa20 at all, and the fact that a SSE2
implementation would almost certainly be much faster on any remotely
modern x86 processor yet no one has cared enough to add one yet, I don't
think it's worthwhile to keep.

Thus, just remove both the x86_64 and i686 salsa20-asm implementations.

Reported-by: syzbot+ffa3a158337bbc01ff09@syzkaller.appspotmail.com
Signed-off-by: Eric Biggers &lt;ebiggers@google.com&gt;
Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>xen: setup pv irq ops vector earlier</title>
<updated>2018-07-17T09:48:32+00:00</updated>
<author>
<name>Juergen Gross</name>
<email>jgross@suse.com</email>
</author>
<published>2018-07-12T15:40:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=8d9399b13642eccaf40575f778ccd2fae59bebbc'/>
<id>urn:sha1:8d9399b13642eccaf40575f778ccd2fae59bebbc</id>
<content type='text'>
commit 0ce0bba4e5e0eb9b753bb821785de5d23c494392 upstream.

Setting pv_irq_ops for Xen PV domains should be done as early as
possible in order to support e.g. very early printk() usage.

The same applies to xen_vcpu_info_reset(0), as it is needed for the
pv irq ops.

Move the call of xen_setup_machphys_mapping() after initializing the
pv functions as it contains a WARN_ON(), too.

Remove the no longer necessary conditional in xen_init_irq_ops()
from PVH V1 times to make clear this is a PV only function.

Cc: &lt;stable@vger.kernel.org&gt; # 4.14
Signed-off-by: Juergen Gross &lt;jgross@suse.com&gt;
Reviewed-by: Boris Ostrovsky &lt;boris.ostrovsky@oracle.com&gt;
Signed-off-by: Juergen Gross &lt;jgross@suse.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>xen: remove global bit from __default_kernel_pte_mask for pv guests</title>
<updated>2018-07-17T09:48:32+00:00</updated>
<author>
<name>Juergen Gross</name>
<email>jgross@suse.com</email>
</author>
<published>2018-07-02T10:00:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=029da06d0ebe7dc2b2c23c8c8fbf830d98b21cb0'/>
<id>urn:sha1:029da06d0ebe7dc2b2c23c8c8fbf830d98b21cb0</id>
<content type='text'>
commit e69b5d308da72cbf4e7911c3979f9a46d28532af upstream.

When removing the global bit from __supported_pte_mask do the same for
__default_kernel_pte_mask in order to avoid the WARN_ONCE() in
check_pgprot() when setting a kernel pte before having called
init_mem_mapping().

Cc: &lt;stable@vger.kernel.org&gt; # 4.17
Reported-by: Michael Young &lt;m.a.young@durham.ac.uk&gt;
Signed-off-by: Juergen Gross &lt;jgross@suse.com&gt;
Reviewed-by: Boris Ostrovsky &lt;boris.ostrovsky@oracle.com&gt;
Signed-off-by: Juergen Gross &lt;jgross@suse.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>arm64: neon: Fix function may_use_simd() return error status</title>
<updated>2018-07-17T09:48:31+00:00</updated>
<author>
<name>Yandong Zhao</name>
<email>yandong77520@gmail.com</email>
</author>
<published>2018-07-11T11:06:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=372c759fdc675be4a3903668e8f6fc476eba3075'/>
<id>urn:sha1:372c759fdc675be4a3903668e8f6fc476eba3075</id>
<content type='text'>
commit 2fd8eb4ad87104c54800ef3cea498c92eb15c78a upstream.

It does not matter if the caller of may_use_simd() migrates to
another cpu after the call, but it is still important that the
kernel_neon_busy percpu instance that is read matches the cpu the
task is running on at the time of the read.

This means that raw_cpu_read() is not sufficient.  kernel_neon_busy
may appear true if the caller migrates during the execution of
raw_cpu_read() and the next task to be scheduled in on the initial
cpu calls kernel_neon_begin().

This patch replaces raw_cpu_read() with this_cpu_read() to protect
against this race.

Cc: &lt;stable@vger.kernel.org&gt;
Fixes: cb84d11e1625 ("arm64: neon: Remove support for nested or hardirq kernel-mode NEON")
Acked-by: Ard Biesheuvel &lt;ard.biesheuvel@linaro.org&gt;
Reviewed-by: Dave Martin &lt;Dave.Martin@arm.com&gt;
Reviewed-by: Mark Rutland &lt;mark.rutland@arm.com&gt;
Signed-off-by: Yandong Zhao &lt;yandong77520@gmail.com&gt;
Signed-off-by: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>x86/purgatory: add missing FORCE to Makefile target</title>
<updated>2018-07-17T09:48:29+00:00</updated>
<author>
<name>Philipp Rudo</name>
<email>prudo@linux.ibm.com</email>
</author>
<published>2018-07-13T23:59:09+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=3f09dcc110f61e4ca97f5563c9affe96161450e7'/>
<id>urn:sha1:3f09dcc110f61e4ca97f5563c9affe96161450e7</id>
<content type='text'>
commit fa8cbda88db12e632a8987c94b66f5caf25bcec4 upstream.

- Build the kernel without the fix
- Add some flag to the purgatories KBUILD_CFLAGS,I used
  -fno-asynchronous-unwind-tables
- Re-build the kernel

When you look at makes output you see that sha256.o is not re-build in the
last step.  Also readelf -S still shows the .eh_frame section for
sha256.o.

With the fix sha256.o is rebuilt in the last step.

Without FORCE make does not detect changes only made to the command line
options.  So object files might not be re-built even when they should be.
Fix this by adding FORCE where it is missing.

Link: http://lkml.kernel.org/r/20180704110044.29279-2-prudo@linux.ibm.com
Fixes: df6f2801f511 ("kernel/kexec_file.c: move purgatories sha256 to common code")
Signed-off-by: Philipp Rudo &lt;prudo@linux.ibm.com&gt;
Acked-by: Dave Young &lt;dyoung@redhat.com&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[4.17+]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>MIPS: Fix ioremap() RAM check</title>
<updated>2018-07-17T09:48:22+00:00</updated>
<author>
<name>Paul Burton</name>
<email>paul.burton@mips.com</email>
</author>
<published>2018-07-05T21:37:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=0c54c6ddd843d37f80406793b3a53bc7c844d8a1'/>
<id>urn:sha1:0c54c6ddd843d37f80406793b3a53bc7c844d8a1</id>
<content type='text'>
commit 523402fa9101090c91d2033b7ebdfdcf65880488 upstream.

We currently attempt to check whether a physical address range provided
to __ioremap() may be in use by the page allocator by examining the
value of PageReserved for each page in the region - lowmem pages not
marked reserved are presumed to be in use by the page allocator, and
requests to ioremap them fail.

The way we check this has been broken since commit 92923ca3aace ("mm:
meminit: only set page reserved in the memblock region"), because
memblock will typically not have any knowledge of non-RAM pages and
therefore those pages will not have the PageReserved flag set. Thus when
we attempt to ioremap a region outside of RAM we incorrectly fail
believing that the region is RAM that may be in use.

In most cases ioremap() on MIPS will take a fast-path to use the
unmapped kseg1 or xkphys virtual address spaces and never hit this path,
so the only way to hit it is for a MIPS32 system to attempt to ioremap()
an address range in lowmem with flags other than _CACHE_UNCACHED.
Perhaps the most straightforward way to do this is using
ioremap_uncached_accelerated(), which is how the problem was discovered.

Fix this by making use of walk_system_ram_range() to test the address
range provided to __ioremap() against only RAM pages, rather than all
lowmem pages. This means that if we have a lowmem I/O region, which is
very common for MIPS systems, we're free to ioremap() address ranges
within it. A nice bonus is that the test is no longer limited to lowmem.

The approach here matches the way x86 performed the same test after
commit c81c8a1eeede ("x86, ioremap: Speed up check for RAM pages") until
x86 moved towards a slightly more complicated check using walk_mem_res()
for unrelated reasons with commit 0e4c12b45aa8 ("x86/mm, resource: Use
PAGE_KERNEL protection for ioremap of memory pages").

Signed-off-by: Paul Burton &lt;paul.burton@mips.com&gt;
Reported-by: Serge Semin &lt;fancer.lancer@gmail.com&gt;
Tested-by: Serge Semin &lt;fancer.lancer@gmail.com&gt;
Fixes: 92923ca3aace ("mm: meminit: only set page reserved in the memblock region")
Cc: James Hogan &lt;jhogan@kernel.org&gt;
Cc: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # v4.2+
Patchwork: https://patchwork.linux-mips.org/patch/19786/
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

</content>
</entry>
<entry>
<title>MIPS: Use async IPIs for arch_trigger_cpumask_backtrace()</title>
<updated>2018-07-17T09:48:22+00:00</updated>
<author>
<name>Paul Burton</name>
<email>paul.burton@mips.com</email>
</author>
<published>2018-06-22T17:55:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.radix-linux.su/BMC/Intel-BMC/linux.git/commit/?id=12cb64bd0eb395dbe13134c3de0c49ae280f5d88'/>
<id>urn:sha1:12cb64bd0eb395dbe13134c3de0c49ae280f5d88</id>
<content type='text'>
commit b63e132b6433a41cf311e8bc382d33fd2b73b505 upstream.

The current MIPS implementation of arch_trigger_cpumask_backtrace() is
broken because it attempts to use synchronous IPIs despite the fact that
it may be run with interrupts disabled.

This means that when arch_trigger_cpumask_backtrace() is invoked, for
example by the RCU CPU stall watchdog, we may:

  - Deadlock due to use of synchronous IPIs with interrupts disabled,
    causing the CPU that's attempting to generate the backtrace output
    to hang itself.

  - Not succeed in generating the desired output from remote CPUs.

  - Produce warnings about this from smp_call_function_many(), for
    example:

    [42760.526910] INFO: rcu_sched detected stalls on CPUs/tasks:
    [42760.535755]  0-...!: (1 GPs behind) idle=ade/140000000000000/0 softirq=526944/526945 fqs=0
    [42760.547874]  1-...!: (0 ticks this GP) idle=e4a/140000000000000/0 softirq=547885/547885 fqs=0
    [42760.559869]  (detected by 2, t=2162 jiffies, g=266689, c=266688, q=33)
    [42760.568927] ------------[ cut here ]------------
    [42760.576146] WARNING: CPU: 2 PID: 1216 at kernel/smp.c:416 smp_call_function_many+0x88/0x20c
    [42760.587839] Modules linked in:
    [42760.593152] CPU: 2 PID: 1216 Comm: sh Not tainted 4.15.4-00373-gee058bb4d0c2 #2
    [42760.603767] Stack : 8e09bd20 8e09bd20 8e09bd20 fffffff0 00000007 00000006 00000000 8e09bca8
    [42760.616937]         95b2b379 95b2b379 807a0080 00000007 81944518 0000018a 00000032 00000000
    [42760.630095]         00000000 00000030 80000000 00000000 806eca74 00000009 8017e2b8 000001a0
    [42760.643169]         00000000 00000002 00000000 8e09baa4 00000008 808b8008 86d69080 8e09bca0
    [42760.656282]         8e09ad50 805e20aa 00000000 00000000 00000000 8017e2b8 00000009 801070ca
    [42760.669424]         ...
    [42760.673919] Call Trace:
    [42760.678672] [&lt;27fde568&gt;] show_stack+0x70/0xf0
    [42760.685417] [&lt;84751641&gt;] dump_stack+0xaa/0xd0
    [42760.692188] [&lt;699d671c&gt;] __warn+0x80/0x92
    [42760.698549] [&lt;68915d41&gt;] warn_slowpath_null+0x28/0x36
    [42760.705912] [&lt;f7c76c1c&gt;] smp_call_function_many+0x88/0x20c
    [42760.713696] [&lt;6bbdfc2a&gt;] arch_trigger_cpumask_backtrace+0x30/0x4a
    [42760.722216] [&lt;f845bd33&gt;] rcu_dump_cpu_stacks+0x6a/0x98
    [42760.729580] [&lt;796e7629&gt;] rcu_check_callbacks+0x672/0x6ac
    [42760.737476] [&lt;059b3b43&gt;] update_process_times+0x18/0x34
    [42760.744981] [&lt;6eb94941&gt;] tick_sched_handle.isra.5+0x26/0x38
    [42760.752793] [&lt;478d3d70&gt;] tick_sched_timer+0x1c/0x50
    [42760.759882] [&lt;e56ea39f&gt;] __hrtimer_run_queues+0xc6/0x226
    [42760.767418] [&lt;e88bbcae&gt;] hrtimer_interrupt+0x88/0x19a
    [42760.775031] [&lt;6765a19e&gt;] gic_compare_interrupt+0x2e/0x3a
    [42760.782761] [&lt;0558bf5f&gt;] handle_percpu_devid_irq+0x78/0x168
    [42760.790795] [&lt;90c11ba2&gt;] generic_handle_irq+0x1e/0x2c
    [42760.798117] [&lt;1b6d462c&gt;] gic_handle_local_int+0x38/0x86
    [42760.805545] [&lt;b2ada1c7&gt;] gic_irq_dispatch+0xa/0x14
    [42760.812534] [&lt;90c11ba2&gt;] generic_handle_irq+0x1e/0x2c
    [42760.820086] [&lt;c7521934&gt;] do_IRQ+0x16/0x20
    [42760.826274] [&lt;9aef3ce6&gt;] plat_irq_dispatch+0x62/0x94
    [42760.833458] [&lt;6a94b53c&gt;] except_vec_vi_end+0x70/0x78
    [42760.840655] [&lt;22284043&gt;] smp_call_function_many+0x1ba/0x20c
    [42760.848501] [&lt;54022b58&gt;] smp_call_function+0x1e/0x2c
    [42760.855693] [&lt;ab9fc705&gt;] flush_tlb_mm+0x2a/0x98
    [42760.862730] [&lt;0844cdd0&gt;] tlb_flush_mmu+0x1c/0x44
    [42760.869628] [&lt;cb259b74&gt;] arch_tlb_finish_mmu+0x26/0x3e
    [42760.877021] [&lt;1aeaaf74&gt;] tlb_finish_mmu+0x18/0x66
    [42760.883907] [&lt;b3fce717&gt;] exit_mmap+0x76/0xea
    [42760.890428] [&lt;c4c8a2f6&gt;] mmput+0x80/0x11a
    [42760.896632] [&lt;a41a08f4&gt;] do_exit+0x1f4/0x80c
    [42760.903158] [&lt;ee01cef6&gt;] do_group_exit+0x20/0x7e
    [42760.909990] [&lt;13fa8d54&gt;] __wake_up_parent+0x0/0x1e
    [42760.917045] [&lt;46cf89d0&gt;] smp_call_function_many+0x1a2/0x20c
    [42760.924893] [&lt;8c21a93b&gt;] syscall_common+0x14/0x1c
    [42760.931765] ---[ end trace 02aa09da9dc52a60 ]---
    [42760.938342] ------------[ cut here ]------------
    [42760.945311] WARNING: CPU: 2 PID: 1216 at kernel/smp.c:291 smp_call_function_single+0xee/0xf8
    ...

This patch switches MIPS' arch_trigger_cpumask_backtrace() to use async
IPIs &amp; smp_call_function_single_async() in order to resolve this
problem. We ensure use of the pre-allocated call_single_data_t
structures is serialized by maintaining a cpumask indicating that
they're busy, and refusing to attempt to send an IPI when a CPU's bit is
set in this mask. This should only happen if a CPU hasn't responded to a
previous backtrace IPI - ie. if it's hung - and we print a warning to
the console in this case.

I've marked this for stable branches as far back as v4.9, to which it
applies cleanly. Strictly speaking the faulty MIPS implementation can be
traced further back to commit 856839b76836 ("MIPS: Add
arch_trigger_all_cpu_backtrace() function") in v3.19, but kernel
versions v3.19 through v4.8 will require further work to backport due to
the rework performed in commit 9a01c3ed5cdb ("nmi_backtrace: add more
trigger_*_cpu_backtrace() methods").

Signed-off-by: Paul Burton &lt;paul.burton@mips.com&gt;
Patchwork: https://patchwork.linux-mips.org/patch/19597/
Cc: James Hogan &lt;jhogan@kernel.org&gt;
Cc: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Cc: Huacai Chen &lt;chenhc@lemote.com&gt;
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # v4.9+
Fixes: 856839b76836 ("MIPS: Add arch_trigger_all_cpu_backtrace() function")
Fixes: 9a01c3ed5cdb ("nmi_backtrace: add more trigger_*_cpu_backtrace() methods")
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;

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