These are only used in uuid.c and vsprintf.c and aren't something modules
should use directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Our "little endian" UUID really is a Wintel GUID, so rename it and its
helpers such (guid_t). The big endian UUID is the only true one, so
give it the name uuid_t. The uuid_le and uuid_be names are retained for
now, but will hopefully go away soon. The exception to that are the _cmp
helpers that will be replaced by better primitives ASAP and thus don't
get the new names.
Also the _to_bin helpers are named to match the better named uuid_parse
routine in userspace.
Also remove the existing typedef in XFS that's now been superceeded by
the generic type name.
Signed-off-by: Christoph Hellwig <hch@lst.de>
[andy: also update the UUID_LE/UUID_BE macros including fallout]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
We don't use uuid_be and the UUID_BE constants in any uapi headers, so make
them private to the kernel.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
The md private helper uuid_equal() collides with a generic helper
of the same name.
Rename the md private helper to md_uuid_equal() and do the same for
md_sb_equal().
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
It really makes no sense to have cls_act enabled without cls. In that
case, the cls_act code is dead. So select it.
This also fixes an issue recently reported by kbuild robot:
[linux-next:master 1326/4151] net/sched/act_api.c:37:18: error: implicit declaration of function 'tcf_chain_get'
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: db50514f9a ("net: sched: add termination action to allow goto chain")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This essentially is a partial revert of commit ff548773
("afs: Move UUID struct to linux/uuid.h") and moves struct uuid_v1 back into
fs/afs as struct afs_uuid. It however keeps it as big endian structure
so that we can use the normal uuid generation helpers when casting to/from
struct afs_uuid.
The V1 uuid intrepretation in struct form isn't really useful to the
rest of the kernel, and not really compatible to it either, so move it
back to AFS instead of polluting the global uuid.h.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: David Howells <dhowells@redhat.com>
commit d91824c08f ("genetlink: register family ops as array") removed the
ops_list member from both genl_family and genl_ops; while the
documentation of genl_family was updated accordingly by this patch,
ops_list remained in the documentation of the genl_ops object.
This patch fixes it by removing ops_list from genl_ops documentation.
Signed-off-by: Rami Rosen <rami.rosen@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Update tcp.txt to fix mandatory congestion control ops and default
CCA selection. Also, fix comment in tcp.h for undo_cwnd.
Signed-off-by: Anmol Sarma <me@anmolsarma.in>
Signed-off-by: David S. Miller <davem@davemloft.net>
Make it possible for a client to use AuriStor's service upgrade facility.
The client does this by adding an RXRPC_UPGRADE_SERVICE control message to
the first sendmsg() of a call. This takes no parameters.
When recvmsg() starts returning data from the call, the service ID field in
the returned msg_name will reflect the result of the upgrade attempt. If
the upgrade was ignored, srx_service will match what was set in the
sendmsg(); if the upgrade happened the srx_service will be altered to
indicate the service the server upgraded to.
Note that:
(1) The choice of upgrade service is up to the server
(2) Further client calls to the same server that would share a connection
are blocked if an upgrade probe is in progress.
(3) This should only be used to probe the service. Clients should then
use the returned service ID in all subsequent communications with that
server (and not set the upgrade). Note that the kernel will not
retain this information should the connection expire from its cache.
(4) If a server that supports upgrading is replaced by one that doesn't,
whilst a connection is live, and if the replacement is running, say,
OpenAFS 1.6.4 or older or an older IBM AFS, then the replacement
server will not respond to packets sent to the upgraded connection.
At this point, calls will time out and the server must be reprobed.
Signed-off-by: David Howells <dhowells@redhat.com>
Implement AuriStor's service upgrade facility. There are three problems
that this is meant to deal with:
(1) Various of the standard AFS RPC calls have IPv4 addresses in their
requests and/or replies - but there's no room for including IPv6
addresses.
(2) Definition of IPv6-specific RPC operations in the standard operation
sets has not yet been achieved.
(3) One could envision the creation a new service on the same port that as
the original service. The new service could implement improved
operations - and the client could try this first, falling back to the
original service if it's not there.
Unfortunately, certain servers ignore packets addressed to a service
they don't implement and don't respond in any way - not even with an
ABORT. This means that the client must then wait for the call timeout
to occur.
What service upgrade does is to see if the connection is marked as being
'upgradeable' and if so, change the service ID in the server and thus the
request and reply formats. Note that the upgrade isn't mandatory - a
server that supports only the original call set will ignore the upgrade
request.
In the protocol, the procedure is then as follows:
(1) To request an upgrade, the first DATA packet in a new connection must
have the userStatus set to 1 (this is normally 0). The userStatus
value is normally ignored by the server.
(2) If the server doesn't support upgrading, the reply packets will
contain the same service ID as for the first request packet.
(3) If the server does support upgrading, all future reply packets on that
connection will contain the new service ID and the new service ID will
be applied to *all* further calls on that connection as well.
(4) The RPC op used to probe the upgrade must take the same request data
as the shadow call in the upgrade set (but may return a different
reply). GetCapability RPC ops were added to all standard sets for
just this purpose. Ops where the request formats differ cannot be
used for probing.
(5) The client must wait for completion of the probe before sending any
further RPC ops to the same destination. It should then use the
service ID that recvmsg() reported back in all future calls.
(6) The shadow service must have call definitions for all the operation
IDs defined by the original service.
To support service upgrading, a server should:
(1) Call bind() twice on its AF_RXRPC socket before calling listen().
Each bind() should supply a different service ID, but the transport
addresses must be the same. This allows the server to receive
requests with either service ID.
(2) Enable automatic upgrading by calling setsockopt(), specifying
RXRPC_UPGRADEABLE_SERVICE and passing in a two-member array of
unsigned shorts as the argument:
unsigned short optval[2];
This specifies a pair of service IDs. They must be different and must
match the service IDs bound to the socket. Member 0 is the service ID
to upgrade from and member 1 is the service ID to upgrade to.
Signed-off-by: David Howells <dhowells@redhat.com>
Permit bind() to be called on an AF_RXRPC socket more than once (currently
maximum twice) to bind multiple listening services to it. There are some
restrictions:
(1) All bind() calls involved must have a non-zero service ID.
(2) The service IDs must all be different.
(3) The rest of the address (notably the transport part) must be the same
in all (a single UDP socket is shared).
(4) This must be done before listen() or sendmsg() is called.
This allows someone to connect to the service socket with different service
IDs and lays the foundation for service upgrading.
The service ID used by an incoming call can be extracted from the msg_name
returned by recvmsg().
Signed-off-by: David Howells <dhowells@redhat.com>
Keep the rxrpc_connection struct's idea of the service ID that is exposed
in the protocol separate from the service ID that's used as a lookup key.
This allows the protocol service ID on a client connection to get upgraded
without making the connection unfindable for other client calls that also
would like to use the upgraded connection.
The connection's actual service ID is then returned through recvmsg() by
way of msg_name.
Whilst we're at it, we get rid of the last_service_id field from each
channel. The service ID is per-connection, not per-call and an entire
connection is upgraded in one go.
Signed-off-by: David Howells <dhowells@redhat.com>
Commit c5a2ee7dde (cpufreq: intel_pstate: Active mode P-state
limits rework) incorrectly assumed that pstate.turbo_pstate would
always be nonzero for CPU0 in min_perf_pct_min() if
cpufreq_register_driver() had succeeded which may not be the case
in virtualized environments.
If that assumption doesn't hold, it leads to an early crash on boot
in intel_pstate_register_driver(), so add a sanity check to
min_perf_pct_min() to prevent the crash from happening.
Fixes: c5a2ee7dde (cpufreq: intel_pstate: Active mode P-state limits rework)
Reported-and-tested-by: Jongman Heo <jongman.heo@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Commit 3fde2999fa ("arm64: cpufeature: Don't dump useless backtrace on
CPU_OUT_OF_SPEC") changed the cpufeature detection code to use add_taint
instead of WARN_TAINT_ONCE when detecting a heterogeneous system with
mismatched feature support. Unfortunately, this resulted in all systems
getting the taint, regardless of any feature mismatch.
This patch fixes the problem by conditionalising the taint on detecting
a feature mismatch.
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
scpi_ops now provide APIs to get the transition_latency and to add
OPPs to the devices making those logic redundant here.
This patch makes use of those APIs and removes the redundant code in
this driver.
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Currently only CPU devices use the transition latency and the OPPs
populated in the SCPI driver. scpi-cpufreq has logic to handle these.
However, even GPU and other users of SCPI DVFS will need the same logic.
In order to avoid duplication, this patch adds support to get DVFS
transition latency and add all the OPPs to the device using OPP library
helper functions. The helper functions added here can be used for any
device whose DVFS are managed by SCPI.
Also, we also have incorrect dependency on the cluster identifier for
the CPUs. It's fundamentally wrong as the domain id need not match the
cluster id. This patch gets rid of that dependency by making use of the
clock bindings which are already in place.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
These two functions implement the same semantics, so unify their naming so we
can share code that calls them. The longer name is more descriptive so use it.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
As reported by Patrice, the header layout of the decompressor is
incorrect when building for v7-M. In this case, the __nop macro
resolves to 'mov r0, r0', which is emitted as a narrow encoding,
resulting in the header data fields to end up at lower offsets than
required.
Given the variety of targets we need to support with the same code,
the startup sequence is a bit of a jumble, and uses instructions
and macros whose encoding widths cannot be specified (badr), or only
exist in a narrow encoding (bx)
So force the use of a wide encoding in __nop, and replace the start
sequence with a simple jump to the label marking the start of code,
preceded by a Thumb2 mode switch if required (using explicit wide
encodings where appropriate). The label itself can be moved to the
start of code [where it belongs] due to the larger range of branch
instructions as compared to adr instructions.
Reported-by: Patrice CHOTARD <patrice.chotard@st.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
NOMMU build leads to the following error:
CC drivers/pci/mmap.o
drivers/pci/mmap.c: In function 'pci_mmap_resource_range':
drivers/pci/mmap.c:60:3: error: implicit declaration of function 'pgprot_device' [-Werror=implicit-function-declaration]
vma->vm_page_prot = pgprot_device(vma->vm_page_prot);
^
cc1: some warnings being treated as errors
scripts/Makefile.build:302: recipe for target 'drivers/pci/mmap.o' failed
make[2]: *** [drivers/pci/mmap.o] Error 1
scripts/Makefile.build:561: recipe for target 'drivers/pci' failed
make[1]: *** [drivers/pci] Error 2
Makefile:1016: recipe for target 'drivers' failed
make: *** [drivers] Error 2
Fix it with support of pgprot_device() macro for NOMMU.
Fixes: 00d2904ffe ("ARM/PCI: Use generic pci_mmap_resource_range()")
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Add support in pte_alloc_one() and pgd_alloc() by
passing __GFP_ACCOUNT in the flags
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Introduce a helper pgtable_gfp_flags() which
just returns the current gfp flags and adds
__GFP_ACCOUNT to account for page table allocation.
The generic helper is added to include/asm/pgalloc.h
and has two variants - WARNING ugly bits ahead
1. If the header is included from a module, no check
for mm == &init_mm is done, since init_mm is not
exported
2. For kernel includes, the check is done and required
see (3e79ec7 arch: x86: charge page tables to kmemcg)
The fundamental assumption is that no module should be
doing pgd/pud/pmd and pte alloc's on behalf of init_mm
directly.
NOTE: This adds an overhead to pmd/pud/pgd allocations
similar to x86. The other alternative was to implement
pmd_alloc_kernel/pud_alloc_kernel and pgd_alloc_kernel
with their offset variants.
For 4k page size, pte_alloc_one no longer calls
pte_alloc_one_kernel.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Currently in hpte_need_flush() if there is no batch pending we always do a
global TLB flush, which is inefficient if the mm has never run on another
thread.
Instead do the same check that __flush_tlb_pending() does and check if a local
flush is sufficient when batch->active is false. Instead of open-coding it we
use mm_is_thread_local().
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
[mpe: Don't use a local, just inline mm_is_thread_local()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Many DRM drivers have common code to make a stub connector
implementation that wraps a drm_panel. By wrapping the panel in a DRM
bridge, all of the connector code (including calls during encoder
enable/disable) goes away.
v2: Fix build with CONFIG_DRM=m, drop "dev" argument that should just
be the panel's dev, move kerneldoc up a level and document
_remove().
v3: Fix another breakage with CONFIG_DRM=m, fix breakage with
CONFIG_OF=n, move protos under CONFIG_DRM_PANEL_BRIDGE, wrap a
line.
Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
Acked-by: Archit Taneja <architt@codeaurora.org> (v2)
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170602202514.11900-1-eric@anholt.net
When PCID is enabled, CR3's PCID bits can change during context
switches, so KVM won't be able to treat CR3 as a per-mm constant any
more.
I structured this like the existing CR4 handling. Under ordinary
circumstances (PCID disabled or if the current PCID and the value
that's already in the VMCS match), then we won't do an extra VMCS
write, and we'll never do an extra direct CR3 read. The overhead
should be minimal.
I disallowed using the new helper in non-atomic context because
PCID support will cause CR3 to stop being constant in non-atomic
process context.
(Frankly, it also scares me a bit that KVM ever treated CR3 as
constant, but it looks like it was okay before.)
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Lazy TLB state is currently managed in a rather baroque manner.
AFAICT, there are three possible states:
- Non-lazy. This means that we're running a user thread or a
kernel thread that has called use_mm(). current->mm ==
current->active_mm == cpu_tlbstate.active_mm and
cpu_tlbstate.state == TLBSTATE_OK.
- Lazy with user mm. We're running a kernel thread without an mm
and we're borrowing an mm_struct. We have current->mm == NULL,
current->active_mm == cpu_tlbstate.active_mm, cpu_tlbstate.state
!= TLBSTATE_OK (i.e. TLBSTATE_LAZY or 0). The current cpu is set
in mm_cpumask(current->active_mm). CR3 points to
current->active_mm->pgd. The TLB is up to date.
- Lazy with init_mm. This happens when we call leave_mm(). We
have current->mm == NULL, current->active_mm ==
cpu_tlbstate.active_mm, but that mm is only relelvant insofar as
the scheduler is tracking it for refcounting. cpu_tlbstate.state
!= TLBSTATE_OK. The current cpu is clear in
mm_cpumask(current->active_mm). CR3 points to swapper_pg_dir,
i.e. init_mm->pgd.
This patch simplifies the situation. Other than perf, x86 stops
caring about current->active_mm at all. We have
cpu_tlbstate.loaded_mm pointing to the mm that CR3 references. The
TLB is always up to date for that mm. leave_mm() just switches us
to init_mm. There are no longer any special cases for mm_cpumask,
and switch_mm() switches mms without worrying about laziness.
After this patch, cpu_tlbstate.state serves only to tell the TLB
flush code whether it may switch to init_mm instead of doing a
normal flush.
This makes fairly extensive changes to xen_exit_mmap(), which used
to look a bit like black magic.
Perf is unchanged. With or without this change, perf may behave a bit
erratically if it tries to read user memory in kernel thread context.
We should build on this patch to teach perf to never look at user
memory when cpu_tlbstate.loaded_mm != current->mm.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The UP asm/tlbflush.h generates somewhat nicer code than the SMP version.
Aside from that, it's fallen quite a bit behind the SMP code:
- flush_tlb_mm_range() didn't flush individual pages if the range
was small.
- The lazy TLB code was much weaker. This usually wouldn't matter,
but, if a kernel thread flushed its lazy "active_mm" more than
once (due to reclaim or similar), it wouldn't be unlazied and
would instead pointlessly flush repeatedly.
- Tracepoints were missing.
Aside from that, simply having the UP code around was a maintanence
burden, since it means that any change to the TLB flush code had to
make sure not to break it.
Simplify everything by deleting the UP code.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The local flush path is very similar to the remote flush path.
Merge them.
This is intended to make no difference to behavior whatsoever. It
removes some code and will make future changes to the flushing
mechanics simpler.
This patch does remove one small optimization: flush_tlb_mm_range()
now has an unconditional smp_mb() instead of using MOV to CR3 or
INVLPG as a full barrier when applicable. I think this is okay for
a few reasons. First, smp_mb() is quite cheap compared to the cost
of a TLB flush. Second, this rearrangement makes a bigger
optimization available: with some work on the SMP function call
code, we could do the local and remote flushes in parallel. Third,
I'm planning a rework of the TLB flush algorithm that will require
an atomic operation at the beginning of each flush, and that
operation will replace the smp_mb().
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Rather than passing all the contents of flush_tlb_info to
flush_tlb_others(), pass a pointer to the structure directly. For
consistency, this also removes the unnecessary cpu parameter from
uv_flush_tlb_others() to make its signature match the other
*flush_tlb_others() functions.
This serves two purposes:
- It will dramatically simplify future patches that change struct
flush_tlb_info, which I'm planning to do.
- struct flush_tlb_info is an adequate description of what to do
for a local flush, too, so by reusing it we can remove duplicated
code between local and remove flushes in a future patch.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
[ Fix build warning. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When the tick is stopped and we reach the dynticks evaluation code on
IRQ exit, we perform a soft tick restart if we observe an expired timer
from there. It means we program the nearest possible tick but we stay in
dynticks mode (ts->tick_stopped = 1) because we may need to stop the tick
again after that expired timer is handled.
Now this solution works most of the time but if we suffer an IRQ storm
and those interrupts trigger faster than the hardware clockevents min
delay, our tick won't fire until that IRQ storm is finished.
Here is the problem: on IRQ exit we reprog the timer to at least
NOW() + min_clockevents_delay. Another IRQ fires before the tick so we
reschedule again to NOW() + min_clockevents_delay, etc... The tick
is eternally rescheduled min_clockevents_delay ahead.
A solution is to simply remove this soft tick restart. After all
the normal dynticks evaluation path can handle 0 delay just fine. And
by doing that we benefit from the optimization branch which avoids
clock reprogramming if the clockevents deadline hasn't changed since
the last reprog. This fixes our issue because we don't do repetitive
clock reprog that always add hardware min delay.
As a side effect it should even optimize the 0 delay path in general.
Reported-and-tested-by: Octavian Purdila <octavian.purdila@nxp.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1496328429-13317-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
