All People I know including myself took a long time to figure out that
typical wakeup will always go to fast path and never go to slow path
except WF_FORK and WF_EXEC.
Vincent reminded me once in a linaro meeting and made me understand
slow path won't happen for WF_TTWU. But my other friends repeatedly
wasted a lot of time on testing this path like me before I reminded
them.
So obviously the code needs some document.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211016111109.5559-1-21cnbao@gmail.com
Add a new helper to deal with the swiotlb case. This keeps the code
nicely boundled and removes the not required call to
dma_direct_optimal_gfp_mask for the swiotlb case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
swiotlb_alloc and swiotlb_free are properly stubbed out if
CONFIG_DMA_RESTRICTED_POOL is not set, so skip the extra checks.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Instead of blindly running into a blocking operation for a non-blocking gfp,
return NULL and spew an error. Note that Kconfig prevents this for all
currently relevant platforms, and this is just a debug check.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
If the architecture can't remap or set an address uncached there is no way
to fullfill a request for a coherent allocation. Return NULL in that case.
Note that this case currently does not happen, so this is a theoretical
fixup and/or a preparation for eventually supporting platforms that
can't support coherent allocations with the generic code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Add a big central !dev_is_dma_coherent(dev) block to deal with as much
as of the uncached allocation schemes and document the schemes a bit
better.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Split the code for DMA_ATTR_NO_KERNEL_MAPPING allocations into a separate
helper to make dma_direct_alloc a little more readable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: David Rientjes <rientjes@google.com>
Add two local variables to track if we want to remap the returned
address using vmap or call dma_set_uncached and use that to simplify
the code flow.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
We must never let unencrypted memory go back into the general page pool.
So if we fail to set it back to encrypted when freeing DMA memory, leak
the memory instead and warn the user.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Remapped allocations handle the encrypted bit through the pgprot passed
to vmap, so there is no call dma_set_decrypted. Note that this case is
currently entirely theoretical as no valid kernel configuration supports
remapped allocations and memory encryption currently.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Factor out helpers the make dealing with memory encryption a little less
cumbersome.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
When CONFIG_DEBUG_INFO_BTF_MODULES is not set
the following warning can be seen:
kernel/bpf/btf.c:6588:13: warning: 'purge_cand_cache' defined but not used [-Wunused-function]
Fix it.
Fixes: 1e89106da2 ("bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn().")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211207014839.6976-1-alexei.starovoitov@gmail.com
Instead of invoking a synchronize_rcu() to free a pointer
after a grace period we can directly make use of new API
that does the same but in more efficient way.
Link: https://lkml.kernel.org/r/20211124110308.2053-10-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
To be consistent with kprobes and eprobes, use
trace_event_buffer_reserver() and trace_event_buffer_commit(). This will
ensure that any updates to trace events will also be implemented on uprobe
events.
Link: https://lkml.kernel.org/r/20211206162440.69fbf96c@gandalf.local.home
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
As kprobe events use trace_event_buffer_commit() to commit the event to
the ftrace ring buffer, for consistency, it should use
trace_event_buffer_reserve() to allocate it, as the two functions are
related.
Link: https://lkml.kernel.org/r/20211130024319.257430762@goodmis.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The eprobes open code the reserving of the event on the ring buffer for
ftrace instead of using the ftrace event wrappers, which means that it
doesn't get affected by the filters, breaking the filtering logic on user
space.
Link: https://lkml.kernel.org/r/20211130024319.068451680@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
In case trace_event_buffer_lock_reserve() is called with preemption
enabled, the algorithm that defines the usage of the per cpu filter buffer
may fail if the task schedules to another CPU after determining which
buffer it will use.
Disable preemption when using the filter buffer. And because that same
buffer must be used throughout the call, keep preemption disabled until
the filter buffer is released.
This will also keep the semantics between the use case of when the filter
buffer is used, and when the ring buffer itself is used, as that case also
disables preemption until the ring buffer is released.
Link: https://lkml.kernel.org/r/20211130024318.880190623@goodmis.org
[ Fixed warning of assignment in if statement
Reported-by: kernel test robot <lkp@intel.com> ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The value read by this_cpu_read() is used later and its use is expected to
stay on the same CPU as being read. But this_cpu_read() does not warn if
it is called without preemption disabled, where as __this_cpu_read() will
check if preemption is disabled on CONFIG_DEBUG_PREEMPT
Currently all callers have preemption disabled, but there may be new
callers in the future that may not.
Link: https://lkml.kernel.org/r/20211130024318.698165354@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add '__rel_loc' using trace event macros. These macros are usually
not used in the kernel, except for testing purpose.
This also add "rel_" variant of macros for dynamic_array string,
and bitmask.
Link: https://lkml.kernel.org/r/163757342119.510314.816029622439099016.stgit@devnote2
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add '__rel_loc' new dynamic data location attribute which encodes
the data location from the next to the field itself.
The '__data_loc' is used for encoding the dynamic data location on
the trace event record. But '__data_loc' is not useful if the writer
doesn't know the event header (e.g. user event), because it records
the dynamic data offset from the entry of the record, not the field
itself.
This new '__rel_loc' attribute encodes the data location relatively
from the next of the field. For example, when there is a record like
below (the number in the parentheses is the size of fields)
|header(N)|common(M)|fields(K)|__data_loc(4)|fields(L)|data(G)|
In this case, '__data_loc' field will be
__data_loc = (G << 16) | (N+M+K+4+L)
If '__rel_loc' is used, this will be
|header(N)|common(M)|fields(K)|__rel_loc(4)|fields(L)|data(G)|
where
__rel_loc = (G << 16) | (L)
This case shows L bytes after the '__rel_loc' attribute field,
if there is no fields after the __rel_loc field, L must be 0.
This is relatively easy (and no need to consider the kernel header
change) when the event data fields are composed by user who doesn't
know header and common fields.
Link: https://lkml.kernel.org/r/163757341258.510314.4214431827833229956.stgit@devnote2
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Branch data available to BPF programs can be very useful to get stack traces
out of userspace application.
Commit fff7b64355 ("bpf: Add bpf_read_branch_records() helper") added BPF
support to capture branch records in x86. Enable this feature also for other
architectures as well by removing checks specific to x86.
If an architecture doesn't support branch records, bpf_read_branch_records()
still has appropriate checks and it will return an -EINVAL in that scenario.
Based on UAPI helper doc in include/uapi/linux/bpf.h, unsupported architectures
should return -ENOENT in such case. Hence, update the appropriate check to
return -ENOENT instead.
Selftest 'perf_branches' result on power9 machine which has the branch stacks
support:
- Before this patch:
[command]# ./test_progs -t perf_branches
#88/1 perf_branches/perf_branches_hw:FAIL
#88/2 perf_branches/perf_branches_no_hw:OK
#88 perf_branches:FAIL
Summary: 0/1 PASSED, 0 SKIPPED, 1 FAILED
- After this patch:
[command]# ./test_progs -t perf_branches
#88/1 perf_branches/perf_branches_hw:OK
#88/2 perf_branches/perf_branches_no_hw:OK
#88 perf_branches:OK
Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED
Selftest 'perf_branches' result on power9 machine which doesn't have branch
stack report:
- After this patch:
[command]# ./test_progs -t perf_branches
#88/1 perf_branches/perf_branches_hw:SKIP
#88/2 perf_branches/perf_branches_no_hw:OK
#88 perf_branches:OK
Summary: 1/1 PASSED, 1 SKIPPED, 0 FAILED
Fixes: fff7b64355 ("bpf: Add bpf_read_branch_records() helper")
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211206073315.77432-1-kjain@linux.ibm.com
The variable @bcon has two meanings. It is used several times for iterating
the list of registered consoles. In the meantime, it holds the information
whether a boot console is first in @console_drivers list.
The information about the 1st console driver used to be important for
the decision whether to install the new console by default or not.
It allowed to re-evaluate the variable @need_default_console when
a real console with tty binding has been unregistered in the meantime.
The decision about the default console is not longer affected by @bcon
variable. The current code checks whether the first driver is real
and has tty binding directly.
The information about the first console is still used for two more
decisions:
1. It prevents duplicate output on non-boot consoles with
CON_CONSDEV flag set.
2. Early/boot consoles are unregistered when a real console with
CON_CONSDEV is registered and @keep_bootcon is not set.
The behavior in the real life is far from obvious. @bcon is set according
to the first console @console_drivers list. But the first position in
the list is special:
1. Consoles with CON_CONSDEV flag are put at the beginning of
the list. It is either the preferred console or any console
with tty binding registered by default.
2. Another console might become the first in the list when
the first console in the list is unregistered. It might
happen either explicitly or automatically when boot
consoles are unregistered.
There is one more important rule:
+ Boot consoles can't be registered when any real console
is already registered.
It is a puzzle. The main complication is the dependency on the first
position is the list and the complicated rules around it.
Let's try to make it easier:
1. Add variable @bootcon_enabled and set it by iterating all registered
consoles. The variable has obvious meaning and more predictable
behavior. Any speed optimization and other tricks are not worth it.
2. Use a generic name for the variable that is used to iterate
the list on registered console drivers.
Behavior change:
No, maybe surprisingly, there is _no_ behavior change!
Let's provide the proof by contradiction. Both operations, duplicate
output prevention and boot consoles removal, are done only when
the newly added console has CON_CONSDEV flag set. The behavior
would change when the new @bootcon_enabled has different value
than the original @bcon.
By other words, the behavior would change when the following conditions
are true:
+ a console with CON_CONSDEV flag is added
+ a real (non-boot) console is the first in the list
+ a boot console is later in the list
Now, a real console might be first in the list only when:
+ It was the first registered console. In this case, there can't be
any boot console because any later ones were rejected.
+ It was put at the first position because it had CON_CONSDEV flag
set. It was either the preferred console or it was a console with
tty binding registered by default. We are interested only in
a real consoles here. And real console with tty binding fulfills
conditions of the default console.
Now, there is always only one console that is either preferred
or fulfills conditions of the default console. It can't be already
in the list and being registered at the same time.
As a result, the above three conditions could newer be "true" at
the same time. Therefore the behavior can't change.
Final dilemma:
OK, the new code has the same behavior. But is the change in the right
direction? What if the handling of @console_drivers is updated in
the future?
OK, let's look at it from another angle:
1. The ordering of @console_drivers list is important only in
console_device() function. The first console driver with tty
binding gets associated with /dev/console.
2. CON_CONSDEV flag is shown in /proc/consoles. And it should be set
for the driver that is returned by console_device().
3. A boot console is removed and the duplicated output is prevented
when the real console with CON_CONSDEV flag is registered.
Now, in the ideal world:
+ The driver associated with /dev/console should be either a console
preferred via the command line, device tree, or SPCR. Or it should
be the first real console with tty binding registered by default.
+ The code should match the related boot and real console drivers.
It should unregister only the obsolete boot driver. And the duplicated
output should be prevented only on the related real driver.
It is clear that it is not guaranteed by the current code. Instead,
the current code looks like a maze of heuristics that try to achieve
the above.
It is result of adding several features over last few decades. For example,
a possibility to register more consoles, unregister consoles, boot
consoles, consoles without tty binding, device tree, SPCR, braille
consoles.
Anyway, there is no reason why the decision, about removing boot consoles
and preventing duplicated output, should depend on the first console
in the list. The current code does the decisions primary by CON_CONSDEV
flag that is used for the preferred console. It looks like a
good compromise. And the change seems to be in the right direction.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211122132649.12737-6-pmladek@suse.com
The variable @need_default_console is used to decide whether a newly
registered console should get enabled by default.
The logic is complicated. It can be modified in a register_console()
call. But it is always re-evaluated in the next call by the following
condition:
if (need_default_console || bcon || !console_drivers)
need_default_console = preferred_console < 0;
In short, the value is updated when either of the condition is valid:
+ the value is still, or again, "true"
+ boot/early console is still the first in @console_driver list
+ @console_driver list is empty
The value is updated according to @preferred_console. In particular,
it is set to "false" when a @preferred_console was set by
__add_preferred_console(). This happens when a non-braille console
was added via the command line, device tree, or SPCR.
It far from clear what this all means together. Let's look at
@need_default_console from another angle:
1. The value is "true" by default. It means that it is always set
according to @preferred_console during the first register_console()
call.
By other words, the first register_console() call will register
the console by default only when none non-braille console was defined
via the command line, device tree, or SPCR.
2. The value will always stay "false" when @preferred_console is set.
By other words, try_enable_default_console() will never get called
when a non-braille console is explicitly required.
4. The value might be set to "false" in try_enable_default_console()
when a console with tty binding (driver) gets enabled.
In this case CON_CONSDEV is set as well. It causes that the console
will be inserted as first into the list @console_driver. It might
be either real or boot/early console.
5. The value will be set _back_ to "true" in the next register_console()
call when:
+ The console added by the previous register_console() had been
a boot/early one.
+ The last console has been unregistered in the meantime and
a boot/early console became first in @console_drivers list
again. Or the list became empty.
By other words, the value will stay "false" only when the last
registered console was real, had tty binding, and was not removed
in the mean time.
The main logic looks clear:
+ Consoles are enabled by default only when no one is preferred
via the command line, device tree, or SPCR.
+ By default, any console is enabled until a real console
with tty binding gets registered.
The behavior when the real console with tty binding is later removed
is a bit unclear:
+ By default, any new console is registered again only when there
is no console or the first console in the list is a boot one.
The question is why the code is suddenly happy when a real console
without tty binding is the first in the list. It looks like an overlook
and bug.
Conclusion:
The state of @preferred_console and the first console in @console_driver
list should be enough to decide whether we need to enable the given console
by default.
The rules are simple. New consoles are _not_ enabled by default
when either of the following conditions is true:
+ @preferred_console is set. It means that a non-braille console
is explicitly configured via the command line, device tree, or SPCR.
+ A real console with tty binding is registered. Such a console will
have CON_CONSDEV flag set and will always be the first in
@console_drivers list.
Note:
The new code does not use @bcon variable. The meaning of the variable
is far from clear. The direct check of the first console in the list
makes it more clear that only real console fulfills requirements
of the default console.
Behavior change:
As already discussed above. There was one situation where the original
code worked a strange way. Let's have:
+ console A: real console without tty binding
+ console B: real console with tty binding
and do:
register_console(A); /* 1st step */
register_console(B); /* 2nd step */
unregister_console(B); /* 3rd step */
register_console(B); /* 4th step */
The original code will not register the console B in the 4th step.
@need_default_console is set to "false" in 2nd step. The real console
with tty binding (driver) is then removed in the 3rd step.
But @need_default_console will stay "false" in the 4th step because
there is no boot/early console and @registered_consoles list is not
empty.
The new code will register the console B in the 4th step because
it checks whether the first console has tty binding (->driver)
This behavior change should acceptable:
1. The scenario requires manual intervention (console removal).
The system should boot with the same consoles as before.
2. Console B is registered again probably because the user wants
to use it. The most likely scenario is that the related
module is reloaded.
3. It makes the behavior more consistent and predictable.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211122132649.12737-5-pmladek@suse.com
There is no need to clear @need_default_console when a console
preferred by the command line, device tree, or SPCR, gets enabled.
The code is called only when some non-braille console matched a console
in @console_cmdline array. It means that a non-braille console was added
in __add_preferred_console() and the variable preferred_console is set
to a number >= 0. As a result, @need_default_console is always set to
"false" in the magic condition:
if (need_default_console || bcon || !console_drivers)
need_default_console = preferred_console < 0;
This is one small step in removing the above magic condition
that is hard to follow.
The patch removes one superfluous assignment and should not change
the functionality.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211122132649.12737-4-pmladek@suse.com
The logic around the variable @has_preferred_console made my head
spin many times. Part of the problem is the ambiguous name.
There is the variable @preferred_console. It points to the last
non-braille console in @console_cmdline array. This array contains
consoles preferred via the command line, device tree, or SPCR.
Then there is the variable @has_preferred_console. It is set to
"true" when @preferred_console is enabled or when a console with
tty binding gets enabled by default.
It might get reset back by the magic condition:
if (!has_preferred_console || bcon || !console_drivers)
has_preferred_console = preferred_console >= 0;
It is a puzzle. Dumb explanation is that it gets re-evaluated
when:
+ it was not set before (see above when it gets set)
+ there is still an early console enabled (bcon)
+ there is no console enabled (!console_drivers)
This is still a puzzle.
It gets more clear when we see where the value is checked. The only
meaning of the variable is to decide whether we should try to enable
the new console by default.
Rename the variable according to the single situation where
the value is checked.
The rename requires an inverted logic. Otherwise, it is a simple
search & replace. It does not change the functionality.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Link: https://lore.kernel.org/r/20211122132649.12737-3-pmladek@suse.com
Put the code enabling a console by default into a separate function
called try_enable_default_console().
Rename try_enable_new_console() to try_enable_preferred_console() to
make the purpose of the different variants more clear.
It is a code refactoring without any functional change.
Signed-off-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Link: https://lore.kernel.org/r/20211122132649.12737-2-pmladek@suse.com
mode runs for prolonged periods with interrupts disabled and ends up
programming the next tick in the past, leading to that storm
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Merge tag 'timers_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Borislav Petkov:
- Prevent a tick storm when a dedicated timekeeper CPU in nohz_full
mode runs for prolonged periods with interrupts disabled and ends up
programming the next tick in the past, leading to that storm
* tag 'timers_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/nohz: Last resort update jiffies on nohz_full IRQ entry
- Fix preempt= callback return values
- Correct utime/stime resource usage reporting on nohz_full to return
the proper times instead of shorter ones
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Merge tag 'sched_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Borislav Petkov:
- Properly init uclamp_flags of a runqueue, on first enqueuing
- Fix preempt= callback return values
- Correct utime/stime resource usage reporting on nohz_full to return
the proper times instead of shorter ones
* tag 'sched_urgent_for_v5.16_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/uclamp: Fix rq->uclamp_max not set on first enqueue
preempt/dynamic: Fix setup_preempt_mode() return value
sched/cputime: Fix getrusage(RUSAGE_THREAD) with nohz_full
BPF_LOG_KERNEL is only used internally, so disallow bpf_btf_load()
to set log level as BPF_LOG_KERNEL. The same checking has already
been done in bpf_check(), so factor out a helper to check the
validity of log attributes and use it in both places.
Fixes: 8580ac9404 ("bpf: Process in-kernel BTF")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20211203053001.740945-1-houtao1@huawei.com
Move the owner_on_cpu() from kernel/locking/rwsem.c into
include/linux/sched.h with under CONFIG_SMP, then use it
in the mutex/rwsem/rtmutex to simplify the code.
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211203075935.136808-2-wangkefeng.wang@huawei.com
There is not really a softirq context on PREEMPT_RT. Softirqs on
PREEMPT_RT are always invoked within the context of a threaded
interrupt handler or within ksoftirqd. The "in-softirq" context is
preemptible and is protected by a per-CPU lock to ensure mutual
exclusion.
There is no difference on PREEMPT_RT between spin_lock_irq() and
spin_lock() because the former does not disable interrupts. Therefore
if a lock is used in_softirq() and locked once with spin_lock_irq()
then lockdep will report this with "inconsistent {SOFTIRQ-ON-W} ->
{IN-SOFTIRQ-W} usage".
Teach lockdep that we don't really do softirqs on -RT.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-6-bigeasy@linutronix.de
The locking selftest for ww-mutex expects to operate directly on the
base-mutex which becomes a rtmutex on PREEMPT_RT.
Add a rtmutex based implementation of mutex_lock_nest_lock() and
mutex_lock_killable() named rt_mutex_lock_nest_lock() abd
rt_mutex_lock_killable().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-5-bigeasy@linutronix.de
Similar to the issues in commits:
6467822b8c ("locking/rtmutex: Prevent spurious EDEADLK return caused by ww_mutexes")
a055fcc132 ("locking/rtmutex: Return success on deadlock for ww_mutex waiters")
ww_rt_mutex_lock() should not return EDEADLK without first going through
the __ww_mutex logic to set the required state. In fact, the chain-walk
can deal with the spurious cycles (per the above commits) this check
warns about and is trying to avoid.
Therefore ignore this test for ww_rt_mutex and simply let things fall
in place.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-4-bigeasy@linutronix.de
rt_rwlock_is_contended() has no users. It makes no sense to use it as
rwlock_is_contended() because it is a sleeping lock on RT and
preemption is possible. It reports always != 0 if used by a writer and
even if there is a waiter then the lock might not be handed over if
the current owner has the highest priority.
Remove rt_rwlock_is_contended().
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-3-bigeasy@linutronix.de
If migrate_enable() is used more often than its counter part then it
remains undetected and rq::nr_pinned will underflow, too.
Add a warning if migrate_enable() is attempted if without a matching a
migrate_disable().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-2-bigeasy@linutronix.de
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread where the selected CPU is the previous one. For asymmetric CPU
capacity systems, the assumption was that the wakee couldn't have a
bigger utilization during task placement than it used to have during the
last activation. That was not considering uclamp.min which can completely
change between two task activations and as a consequence mandates the
fitness criterion asym_fits_capacity(), even for the exit path described
above.
Fixes: b4c9c9f156 ("sched/fair: Prefer prev cpu in asymmetric wakeup path")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211129173115.4006346-1-vincent.donnefort@arm.com
select_idle_sibling() has a special case for tasks woken up by a per-CPU
kthread, where the selected CPU is the previous one. However, the current
condition for this exit path is incomplete. A task can wake up from an
interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A
such scenario would spuriously trigger the special case described above.
Also, a recent change made the idle task like a regular per-CPU kthread,
hence making that situation more likely to happen
(is_per_cpu_kthread(swapper) being true now).
Checking for task context makes sure select_idle_sibling() will not
interpret a wake up from any other context as a wake up by a per-CPU
kthread.
Fixes: 52262ee567 ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression")
Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com
Commit d81ae8aac8 ("sched/uclamp: Fix initialization of struct
uclamp_rq") introduced a bug where uclamp_max of the rq is not reset to
match the woken up task's uclamp_max when the rq is idle.
The code was relying on rq->uclamp_max initialized to zero, so on first
enqueue
static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
enum uclamp_id clamp_id)
{
...
if (uc_se->value > READ_ONCE(uc_rq->value))
WRITE_ONCE(uc_rq->value, uc_se->value);
}
was actually resetting it. But since commit d81ae8aac8 changed the
default to 1024, this no longer works. And since rq->uclamp_flags is
also initialized to 0, neither above code path nor uclamp_idle_reset()
update the rq->uclamp_max on first wake up from idle.
This is only visible from first wake up(s) until the first dequeue to
idle after enabling the static key. And it only matters if the
uclamp_max of this task is < 1024 since only then its uclamp_max will be
effectively ignored.
Fix it by properly initializing rq->uclamp_flags = UCLAMP_FLAG_IDLE to
ensure uclamp_idle_reset() is called which then will update the rq
uclamp_max value as expected.
Fixes: d81ae8aac8 ("sched/uclamp: Fix initialization of struct uclamp_rq")
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20211202112033.1705279-1-qais.yousef@arm.com
__setup() callbacks expect 1 for success and 0 for failure. Correct the
usage here to reflect that.
Fixes: 826bfeb37b ("preempt/dynamic: Support dynamic preempt with preempt= boot option")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211203233203.133581-1-ahalaney@redhat.com
I completed the first batch of signal changes for v5.17 against
v5.16-rc1 before the SA_IMMUTABLE fixes where completed. Which leaves
me with two lines of development that I want on my signal development
branch both rooted at v5.16-rc1. Especially as I am hoping
to reach the point of being able to remove SA_IMMUTABLE.
Linus merged my SA_IMUTABLE fixes as:
7af959b5d5 ("Merge branch 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
To avoid rebasing the development changes that are currently complete I am
merging the work I sent upstream to Linus to make my life simpler.
The SA_IMMUTABLE changes as they are described in Linus's merge commit.
Pull exit-vs-signal handling fixes from Eric Biederman:
"This is a small set of changes where debuggers were no longer able to
intercept synchronous SIGTRAP and SIGSEGV, introduced by the exit
cleanups.
This is essentially the change you suggested with all of i's dotted
and the t's crossed so that ptrace can intercept all of the cases it
has been able to intercept the past, and all of the cases that made it
to exit without giving ptrace a chance still don't give ptrace a
chance"
* 'SA_IMMUTABLE-fixes-for-v5.16-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
signal: Replace force_fatal_sig with force_exit_sig when in doubt
signal: Don't always set SA_IMMUTABLE for forced signals
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
The first commit cited below attempts to fix the off-by-one error that
appeared in some comparisons with an open range. Due to this error,
arithmetically equivalent pieces of code could get different verdicts
from the verifier, for example (pseudocode):
// 1. Passes the verifier:
if (data + 8 > data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
// 2. Rejected by the verifier (should still pass):
if (data + 7 >= data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
The attempted fix, however, shifts the range by one in a wrong
direction, so the bug not only remains, but also such piece of code
starts failing in the verifier:
// 3. Rejected by the verifier, but the check is stricter than in #1.
if (data + 8 >= data_end)
return early
read *(u64 *)data, i.e. [data; data+7]
The change performed by that fix converted an off-by-one bug into
off-by-two. The second commit cited below added the BPF selftests
written to ensure than code chunks like #3 are rejected, however,
they should be accepted.
This commit fixes the off-by-two error by adjusting new_range in the
right direction and fixes the tests by changing the range into the
one that should actually fail.
Fixes: fb2a311a31 ("bpf: fix off by one for range markings with L{T, E} patterns")
Fixes: b37242c773 ("bpf: add test cases to bpf selftests to cover all access tests")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211130181607.593149-1-maximmi@nvidia.com
At CPU-hotplug time, unbind_workers() may preempt a worker while it is
going to sleep. In that case the following scenario can happen:
unbind_workers() wq_worker_sleeping()
-------------- -------------------
if (worker->flags & WORKER_NOT_RUNNING)
return;
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_dec_and_test(&pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of -1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == -1", all sorts of hazards can
happen, starting with queued works being ignored because no workers are
awaken at insert_work() time.
Fix this with checking again the worker flags while pool->lock is locked.
Fixes: b945efcdd0 ("sched: Remove pointless preemption disable in sched_submit_work()")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
At CPU-hotplug time, unbind_worker() may preempt a worker while it is
waking up. In that case the following scenario can happen:
unbind_workers() wq_worker_running()
-------------- -------------------
if (!(worker->flags & WORKER_NOT_RUNNING))
//PREEMPTED by unbind_workers
worker->flags |= WORKER_UNBOUND;
[...]
atomic_set(&pool->nr_running, 0);
//resume to worker
atomic_inc(&worker->pool->nr_running);
After unbind_worker() resets pool->nr_running, the value is expected to
remain 0 until the pool ever gets rebound in case cpu_up() is called on
the target CPU in the future. But here the race leaves pool->nr_running
with a value of 1, triggering the following warning when the worker goes
idle:
WARNING: CPU: 3 PID: 34 at kernel/workqueue.c:1823 worker_enter_idle+0x95/0xc0
Modules linked in:
CPU: 3 PID: 34 Comm: kworker/3:0 Not tainted 5.16.0-rc1+ #34
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
Workqueue: 0x0 (rcu_par_gp)
RIP: 0010:worker_enter_idle+0x95/0xc0
Code: 04 85 f8 ff ff ff 39 c1 7f 09 48 8b 43 50 48 85 c0 74 1b 83 e2 04 75 99 8b 43 34 39 43 30 75 91 8b 83 00 03 00 00 85 c0 74 87 <0f> 0b 5b c3 48 8b 35 70 f1 37 01 48 8d 7b 48 48 81 c6 e0 93 0
RSP: 0000:ffff9b7680277ed0 EFLAGS: 00010086
RAX: 00000000ffffffff RBX: ffff93465eae9c00 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff9346418a0000 RDI: ffff934641057140
RBP: ffff934641057170 R08: 0000000000000001 R09: ffff9346418a0080
R10: ffff9b768027fdf0 R11: 0000000000002400 R12: ffff93465eae9c20
R13: ffff93465eae9c20 R14: ffff93465eae9c70 R15: ffff934641057140
FS: 0000000000000000(0000) GS:ffff93465eac0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000001cc0c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
worker_thread+0x89/0x3d0
? process_one_work+0x400/0x400
kthread+0x162/0x190
? set_kthread_struct+0x40/0x40
ret_from_fork+0x22/0x30
</TASK>
Also due to this incorrect "nr_running == 1", further queued work may
end up not being served, because no worker is awaken at work insert time.
This raises rcutorture writer stalls for example.
Fix this with disabling preemption in the right place in
wq_worker_running().
It's worth noting that if the worker migrates and runs concurrently with
unbind_workers(), it is guaranteed to see the WORKER_UNBOUND flag update
due to set_cpus_allowed_ptr() acquiring/releasing rq->lock.
Fixes: 6d25be5782 ("sched/core, workqueues: Distangle worker accounting from rq lock")
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When module registering its set is built-in, THIS_MODULE will be NULL,
hence we cannot return early in case owner is NULL.
Fixes: 14f267d95f ("bpf: btf: Introduce helpers for dynamic BTF set registration")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211122144742.477787-3-memxor@gmail.com
Vinicius Costa Gomes reported [0] that build fails when
CONFIG_DEBUG_INFO_BTF is enabled and CONFIG_BPF_SYSCALL is disabled.
This leads to btf.c not being compiled, and then no symbol being present
in vmlinux for the declarations in btf.h. Since BTF is not useful
without enabling BPF subsystem, disallow this combination.
However, theoretically disabling both now could still fail, as the
symbol for kfunc_btf_id_list variables is not available. This isn't a
problem as the compiler usually optimizes the whole register/unregister
call, but at lower optimization levels it can fail the build in linking
stage.
Fix that by adding dummy variables so that modules taking address of
them still work, but the whole thing is a noop.
[0]: https://lore.kernel.org/bpf/20211110205418.332403-1-vinicius.gomes@intel.com
Fixes: 14f267d95f ("bpf: btf: Introduce helpers for dynamic BTF set registration")
Reported-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211122144742.477787-2-memxor@gmail.com
Given BPF program's BTF root type name perform the following steps:
. search in vmlinux candidate cache.
. if (present in cache and candidate list >= 1) return candidate list.
. do a linear search through kernel BTFs for possible candidates.
. regardless of number of candidates found populate vmlinux cache.
. if (candidate list >= 1) return candidate list.
. search in module candidate cache.
. if (present in cache) return candidate list (even if list is empty).
. do a linear search through BTFs of all kernel modules
collecting candidates from all of them.
. regardless of number of candidates found populate module cache.
. return candidate list.
Then wire the result into bpf_core_apply_relo_insn().
When BPF program is trying to CO-RE relocate a type
that doesn't exist in either vmlinux BTF or in modules BTFs
these steps will perform 2 cache lookups when cache is hit.
Note the cache doesn't prevent the abuse by the program that might
have lots of relocations that cannot be resolved. Hence cond_resched().
CO-RE in the kernel requires CAP_BPF, since BTF loading requires it.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211201181040.23337-9-alexei.starovoitov@gmail.com
