For the ring buffer iterator (non-consuming read), the event needs to be
copied into the iterator buffer to make sure that a writer does not
overwrite it while the user is reading it. If a write happens during the
copy, the buffer is simply discarded.
But the temp buffer itself was not big enough. The allocation of the
buffer was only BUF_MAX_DATA_SIZE, which is the maximum data size that can
be passed into the ring buffer and saved. But the temp buffer needs to
hold the meta data as well. That would be BUF_PAGE_SIZE and not
BUF_MAX_DATA_SIZE.
Link: https://lore.kernel.org/linux-trace-kernel/20231212072558.61f76493@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 785888c544 ("ring-buffer: Have rb_iter_head_event() handle concurrent writer")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The ring buffer timestamps are synchronized by two timestamp placeholders.
One is the "before_stamp" and the other is the "write_stamp" (sometimes
referred to as the "after stamp" but only in the comments. These two
stamps are key to knowing how to handle nested events coming in with a
lockless system.
When moving across sub-buffers, the before stamp is updated but the write
stamp is not. There's an effort to put back the before stamp to something
that seems logical in case there's nested events. But as the current event
is about to cross sub-buffers, and so will any new nested event that happens,
updating the before stamp is useless, and could even introduce new race
conditions.
The first event on a sub-buffer simply uses the sub-buffer's timestamp
and keeps a "delta" of zero. The "before_stamp" and "write_stamp" are not
used in the algorithm in this case. There's no reason to try to fix the
before_stamp when this happens.
As a bonus, it removes a cmpxchg() when crossing sub-buffers!
Link: https://lore.kernel.org/linux-trace-kernel/20231211114420.36dde01b@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: a389d86f7f ("ring-buffer: Have nested events still record running time stamp")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
If crash_base is equal to CRASH_ADDR_LOW_MAX, it also indicates that
the crashkernel memory is allocated from high memory. However, the
current check only considers the case where crash_base is greater than
CRASH_ADDR_LOW_MAX. Fix it.
The runtime effects is that crashkernel high memory is successfully
reserved, whereas the crashkernel low memory is bypassed in this case,
then kdump kernel bootup will fail because of no low memory under 4G.
This patch also includes some minor cleanups.
Link: https://lkml.kernel.org/r/20231209141438.77233-1-ytcoode@gmail.com
Fixes: 0ab97169aa ("crash_core: add generic function to do reservation")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In commit f8ff23429c62 ("kernel/Kconfig.kexec: drop select of KEXEC for
CRASH_DUMP") we tried to fix a config regression, where CONFIG_CRASH_DUMP
required CONFIG_KEXEC.
However, it was not enough at least for arm64 platforms. While further
testing the patch with our arm64 config I noticed that CONFIG_CRASH_DUMP
is unavailable in menuconfig. This is because CONFIG_CRASH_DUMP still
depends on the new CONFIG_ARCH_SUPPORTS_KEXEC introduced in commit
91506f7e5d ("arm64/kexec: refactor for kernel/Kconfig.kexec") and on
arm64 CONFIG_ARCH_SUPPORTS_KEXEC requires CONFIG_PM_SLEEP_SMP=y, which in
turn requires either CONFIG_SUSPEND=y or CONFIG_HIBERNATION=y neither of
which are set in our config.
Given that we already established that CONFIG_KEXEC (which is a switch for
kexec system call itself) is not required for CONFIG_CRASH_DUMP drop
CONFIG_ARCH_SUPPORTS_KEXEC dependency as well. The arm64 kernel builds
just fine with CONFIG_CRASH_DUMP=y and with both CONFIG_KEXEC=n and
CONFIG_KEXEC_FILE=n after f8ff23429c62 ("kernel/Kconfig.kexec: drop select
of KEXEC for CRASH_DUMP") and this patch are applied given that the
necessary shared bits are included via CONFIG_KEXEC_CORE dependency.
[bhe@redhat.com: don't export some symbols when CONFIG_MMU=n]
Link: https://lkml.kernel.org/r/ZW03ODUKGGhP1ZGU@MiWiFi-R3L-srv
[bhe@redhat.com: riscv, kexec: fix dependency of two items]
Link: https://lkml.kernel.org/r/ZW04G/SKnhbE5mnX@MiWiFi-R3L-srv
Link: https://lkml.kernel.org/r/20231129220409.55006-1-ignat@cloudflare.com
Fixes: 91506f7e5d ("arm64/kexec: refactor for kernel/Kconfig.kexec")
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: <stable@vger.kernel.org> # 6.6+: f8ff234: kernel/Kconfig.kexec: drop select of KEXEC for CRASH_DUMP
Cc: <stable@vger.kernel.org> # 6.6+
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The snapshot buffer is to mimic the main buffer so that when a snapshot is
needed, the snapshot and main buffer are swapped. When the snapshot buffer
is allocated, it is set to the minimal size that the ring buffer may be at
and still functional. When it is allocated it becomes the same size as the
main ring buffer, and when the main ring buffer changes in size, it should
do.
Currently, the resize only updates the snapshot buffer if it's used by the
current tracer (ie. the preemptirqsoff tracer). But it needs to be updated
anytime it is allocated.
When changing the size of the main buffer, instead of looking to see if
the current tracer is utilizing the snapshot buffer, just check if it is
allocated to know if it should be updated or not.
Also fix typo in comment just above the code change.
Link: https://lore.kernel.org/linux-trace-kernel/20231210225447.48476a6a@rorschach.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: ad909e21bb ("tracing: Add internal tracing_snapshot() functions")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reading the ring buffer does a swap of a sub-buffer within the ring buffer
with a empty sub-buffer. This allows the reader to have full access to the
content of the sub-buffer that was swapped out without having to worry
about contention with the writer.
The readers call ring_buffer_alloc_read_page() to allocate a page that
will be used to swap with the ring buffer. When the code is finished with
the reader page, it calls ring_buffer_free_read_page(). Instead of freeing
the page, it stores it as a spare. Then next call to
ring_buffer_alloc_read_page() will return this spare instead of calling
into the memory management system to allocate a new page.
Unfortunately, on freeing of the ring buffer, this spare page is not
freed, and causes a memory leak.
Link: https://lore.kernel.org/linux-trace-kernel/20231210221250.7b9cc83c@rorschach.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 73a757e631 ("ring-buffer: Return reader page back into existing ring buffer")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The maximum ring buffer data size is the maximum size of data that can be
recorded on the ring buffer. Events must be smaller than the sub buffer
data size minus any meta data. This size is checked before trying to
allocate from the ring buffer because the allocation assumes that the size
will fit on the sub buffer.
The maximum size was calculated as the size of a sub buffer page (which is
currently PAGE_SIZE minus the sub buffer header) minus the size of the
meta data of an individual event. But it missed the possible adding of a
time stamp for events that are added long enough apart that the event meta
data can't hold the time delta.
When an event is added that is greater than the current BUF_MAX_DATA_SIZE
minus the size of a time stamp, but still less than or equal to
BUF_MAX_DATA_SIZE, the ring buffer would go into an infinite loop, looking
for a page that can hold the event. Luckily, there's a check for this loop
and after 1000 iterations and a warning is emitted and the ring buffer is
disabled. But this should never happen.
This can happen when a large event is added first, or after a long period
where an absolute timestamp is prefixed to the event, increasing its size
by 8 bytes. This passes the check and then goes into the algorithm that
causes the infinite loop.
For events that are the first event on the sub-buffer, it does not need to
add a timestamp, because the sub-buffer itself contains an absolute
timestamp, and adding one is redundant.
The fix is to check if the event is to be the first event on the
sub-buffer, and if it is, then do not add a timestamp.
This also fixes 32 bit adding a timestamp when a read of before_stamp or
write_stamp is interrupted. There's still no need to add that timestamp if
the event is going to be the first event on the sub buffer.
Also, if the buffer has "time_stamp_abs" set, then also check if the
length plus the timestamp is greater than the BUF_MAX_DATA_SIZE.
Link: https://lore.kernel.org/all/20231212104549.58863438@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20231212071837.5fdd6c13@gandalf.local.home
Link: https://lore.kernel.org/linux-trace-kernel/20231212111617.39e02849@gandalf.local.home
Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: a4543a2fa9 ("ring-buffer: Get timestamp after event is allocated")
Fixes: 58fbc3c632 ("ring-buffer: Consolidate add_timestamp to remove some branches")
Reported-by: Kent Overstreet <kent.overstreet@linux.dev> # (on IRC)
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Linus suggested that the kconfig here is confusing:
https://lore.kernel.org/all/CAHk-=wgUiAtiszwseM1p2fCJ+sC4XWQ+YN4TanFhUgvUqjr9Xw@mail.gmail.com/
Let's break it into three kconfigs controlling distinct things:
- CONFIG_IOMMU_MM_DATA controls if the mm_struct has the additional
fields for the IOMMU. Currently only PASID, but later patches store
a struct iommu_mm_data *
- CONFIG_ARCH_HAS_CPU_PASID controls if the arch needs the scheduling bit
for keeping track of the ENQCMD instruction. x86 will select this if
IOMMU_SVA is enabled
- IOMMU_SVA controls if the IOMMU core compiles in the SVA support code
for iommu driver use and the IOMMU exported API
This way ARM will not enable CONFIG_ARCH_HAS_CPU_PASID
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231027000525.1278806-2-tina.zhang@intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Use the fact that we are passing subprog index around and have
a corresponding struct bpf_subprog_info in bpf_verifier_env for each
subprogram. We don't need to separately pass around a flag whether
subprog is exception callback or not, each relevant verifier function
can determine this using provided subprog index if we maintain
bpf_subprog_info properly.
Also move out exception callback-specific logic from
btf_prepare_func_args(), keeping it generic. We can enforce all these
restriction right before exception callback verification pass. We add
out parameter, arg_cnt, for now, but this will be unnecessary with
subsequent refactoring and will be removed.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231204233931.49758-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
If an SRCU barrier is queued while callbacks are running and a new
callbacks invocator for the same sdp were to run concurrently, the
RCU barrier might execute too early. As this requirement is non-obvious,
make sure to keep a record.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
While in grace period start, there is nothing to accelerate and
therefore no need to advance the callbacks either if no callback is
to be enqueued.
Spare these needless operations in this case.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Callbacks advancing on SRCU must be performed on two specific places:
1) On enqueue time in order to make room for the acceleration of the
new callback.
2) On invocation time in order to move the callbacks ready to invoke.
Any other callback advancing callsite is needless. Remove the remaining
one in srcu_gp_start().
Co-developed-by: Yong He <zhuangel570@gmail.com>
Signed-off-by: Yong He <zhuangel570@gmail.com>
Co-developed-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Co-developed-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
The error variable in snapshot_write_next() gets a value before it is
used, so don't initialize it to 0 upfront.
Signed-off-by: Li zeming <zeming@nfschina.com>
[ rjw: Subject and changelog rewrite ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
'error' first receives the function result before it is used, and it
does not need to be assigned a value during definition.
Signed-off-by: Li zeming <zeming@nfschina.com>
[ rjw: Subject rewrite ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
It is not necessary to intialize the error variable in
create_basic_memory_bitmaps(), because it is only read after
being assigned a value.
Signed-off-by: Wang chaodong <chaodong@nfschina.com>
[ rjw: Subject and changelog rewrite ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Although the RCU CPU stall notifiers can be useful for dumping state when
tracking down delicate forward-progress bugs where NUMA effects cause
cache lines to be delivered to a given CPU regularly, but always in a
state that prevents that CPU from making forward progress. These bugs can
be detected by the RCU CPU stall-warning mechanism, but in some cases,
the stall-warnings printk()s disrupt the forward-progress bug before
any useful state can be obtained.
Unfortunately, the notifier mechanism added by commit 5b404fdaba ("rcu:
Add RCU CPU stall notifier") can make matters worse if used at all
carelessly. For example, if the stall warning was caused by a lock not
being released, then any attempt to acquire that lock in the notifier
will hang. This will prevent not only the notifier from producing any
useful output, but it will also prevent the stall-warning message from
ever appearing.
This commit therefore hides this new RCU CPU stall notifier
mechanism under a new RCU_CPU_STALL_NOTIFIER Kconfig option that
depends on both DEBUG_KERNEL and RCU_EXPERT. In addition, the
rcupdate.rcu_cpu_stall_notifiers=1 kernel boot parameter must also
be specified. The RCU_CPU_STALL_NOTIFIER Kconfig option's help text
contains a warning and explains the dangers of careless use, recommending
lockless notifier code. In addition, a WARN() is triggered each time
that an attempt is made to register a stall-warning notifier in kernels
built with CONFIG_RCU_CPU_STALL_NOTIFIER=y.
This combination of measures will keep use of this mechanism confined to
debug kernels and away from routine deployments.
[ paulmck: Apply Dan Carpenter feedback. ]
Fixes: 5b404fdaba ("rcu: Add RCU CPU stall notifier")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
The task_struct structure's ->rcu_tasks_idle_cpu can be concurrently
read and written from the RCU Tasks grace-period kthread and from the
CPU on which the task_struct structure's task is running. This commit
therefore marks the accesses appropriately.
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Patch series "kexec_file: Load kernel at top of system RAM if required".
Justification:
==============
Kexec_load interface has been doing top down searching and loading
kernel/initrd/purgtory etc to prepare for kexec reboot. In that way, the
benefits are that it avoids to consume and fragment limited low memory
which satisfy DMA buffer allocation and big chunk of continuous memory
during system init; and avoids to stir with BIOS/FW reserved or occupied
areas, or corner case handling/work around/quirk occupied areas when doing
system init. By the way, the top-down searching and loading of kexec-ed
kernel is done in user space utility code.
For kexec_file loading, even if kexec_buf.top_down is 'true', it's simply
ignored. It calls walk_system_ram_res() directly to go through all
resources of System RAM bottom up, to find an available memory region,
then call locate_mem_hole_callback() to allocate memory in that found
memory region from top to down. This is not expected and inconsistent
with kexec_load.
Implementation
===============
In patch 1, introduce a new function walk_system_ram_res_rev() which is a
variant of walk_system_ram_res(), it walks through a list of all the
resources of System RAM in reversed order, i.e., from higher to lower.
In patch 2, check if kexec_buf.top_down is 'true' in
kexec_walk_resources(), if yes, call walk_system_ram_res_rev() to find
memory region of system RAM from top to down to load kernel/initrd etc.
Background information: ======================= And I ever tried this in
the past in a different way, please see below link. In the post, I tried
to adjust struct sibling linking code, replace the the singly linked list
with list_head so that walk_system_ram_res_rev() can be implemented in a
much easier way. Finally I failed.
https://lore.kernel.org/all/20180718024944.577-4-bhe@redhat.com/
This time, I picked up the patch from AKASHI Takahiro's old post and made
some change to take as the current patch 1:
https://lists.infradead.org/pipermail/linux-arm-kernel/2017-September/531456.html
This patch (of 2):
Kexec_load interface has been doing top down searching and loading
kernel/initrd/purgtory etc to prepare for kexec reboot. In that way, the
benefits are that it avoids to consume and fragment limited low memory
which satisfy DMA buffer allocation and big chunk of continuous memory
during system init; and avoids to stir with BIOS/FW reserved or occupied
areas, or corner case handling/work around/quirk occupied areas when doing
system init. By the way, the top-down searching and loading of kexec-ed
kernel is done in user space utility code.
For kexec_file loading, even if kexec_buf.top_down is 'true', it's simply
ignored. It calls walk_system_ram_res() directly to go through all
resources of System RAM bottom up, to find an available memory region,
then call locate_mem_hole_callback() to allocate memory in that found
memory region from top to down. This is not expected and inconsistent
with kexec_load.
Here check if kexec_buf.top_down is 'true' in kexec_walk_resources(), if
yes, call the newly added walk_system_ram_res_rev() to find memory region
of system RAM from top to down to load kernel/initrd etc.
Link: https://lkml.kernel.org/r/20231114091658.228030-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20231114091658.228030-3-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The purpose of recalc_sigpending_and_wake() is not clear, it looks
"obviously unneeded" because we are going to send the signal which can't
be blocked or ignored.
Add the comment to explain why we can't rely on send_signal_locked() and
make this logic more simple/explicit. recalc_sigpending_and_wake() has no
other users, it can die.
In fact I think we don't even need signal_wake_up(), the target task must
be either current or a TASK_TRACED child, otherwise the usage of siglock
is not safe. But this needs another change.
Link: https://lkml.kernel.org/r/20231120151649.GA15995@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When kernel_can_power_off() returns false, and reboot has called with
LINUX_REBOOT_CMD_POWER_OFF, kernel_halt() will be initiated instead of
actual power off function.
However, in this situation, Kernel never explicitly notifies user that
system halted instead of requested power off.
Since halt and power off perform different behavior, and user initiated
reboot call with power off command, not halt, This could be unintended
behavior to user, like this:
~ # poweroff -f
[ 3.581482] reboot: System halted
Therefore, this explicitly notifies user that poweroff is not available,
and halting has been occured as an alternative behavior instead:
~ # poweroff -f
[ 4.123668] reboot: Power off not available: System halted instead
[akpm@linux-foundation.org: tweak comment text]
Link: https://lkml.kernel.org/r/20231104113320.72440-1-ldmldm05@gmail.com
Signed-off-by: Dongmin Lee <ldmldm05@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In dup_mmap(), using __mt_dup() to duplicate the old maple tree and then
directly replacing the entries of VMAs in the new maple tree can result in
better performance. __mt_dup() uses DFS pre-order to duplicate the maple
tree, so it is efficient.
The average time complexity of __mt_dup() is O(n), where n is the number
of VMAs. The proof of the time complexity is provided in the commit log
that introduces __mt_dup(). After duplicating the maple tree, each
element is traversed and replaced (ignoring the cases of deletion, which
are rare). Since it is only a replacement operation for each element,
this process is also O(n).
Analyzing the exact time complexity of the previous algorithm is
challenging because each insertion can involve appending to a node,
pushing data to adjacent nodes, or even splitting nodes. The frequency of
each action is difficult to calculate. The worst-case scenario for a
single insertion is when the tree undergoes splitting at every level. If
we consider each insertion as the worst-case scenario, we can determine
that the upper bound of the time complexity is O(n*log(n)), although this
is a loose upper bound. However, based on the test data, it appears that
the actual time complexity is likely to be O(n).
As the entire maple tree is duplicated using __mt_dup(), if dup_mmap()
fails, there will be a portion of VMAs that have not been duplicated in
the maple tree. To handle this, we mark the failure point with
XA_ZERO_ENTRY. In exit_mmap(), if this marker is encountered, stop
releasing VMAs that have not been duplicated after this point.
There is a "spawn" in byte-unixbench[1], which can be used to test the
performance of fork(). I modified it slightly to make it work with
different number of VMAs.
Below are the test results. The first row shows the number of VMAs. The
second and third rows show the number of fork() calls per ten seconds,
corresponding to next-20231006 and the this patchset, respectively. The
test results were obtained with CPU binding to avoid scheduler load
balancing that could cause unstable results. There are still some
fluctuations in the test results, but at least they are better than the
original performance.
21 121 221 421 821 1621 3221 6421 12821 25621 51221
112100 76261 54227 34035 20195 11112 6017 3161 1606 802 393
114558 83067 65008 45824 28751 16072 8922 4747 2436 1233 599
2.19% 8.92% 19.88% 34.64% 42.37% 44.64% 48.28% 50.17% 51.68% 53.74% 52.42%
[1] https://github.com/kdlucas/byte-unixbench/tree/master
Link: https://lkml.kernel.org/r/20231027033845.90608-11-zhangpeng.00@bytedance.com
Signed-off-by: Peng Zhang <zhangpeng.00@bytedance.com>
Suggested-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Christie <michael.christie@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull scheduler fix from Borislav Petkov:
- Make sure tasks are thawed exactly and only once to avoid their state
getting corrupted
* tag 'sched_urgent_for_v6.7_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
freezer,sched: Do not restore saved_state of a thawed task
Pull perf event fix from Borislav Petkov:
- Make sure perf event size validation is done on every event in the
group
* tag 'perf_urgent_for_v6.7_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Fix perf_event_validate_size()
When verifier validates BPF_ST_MEM instruction that stores known
constant to stack (e.g., *(u64 *)(r10 - 8) = 123), it effectively spills
a fake register with a constant (but initially imprecise) value to
a stack slot. Because read-side logic treats it as a proper register
fill from stack slot, we need to mark such stack slot initialization as
INSN_F_STACK_ACCESS instruction to stop precision backtracking from
missing it.
Fixes: 41f6f64e69 ("bpf: support non-r10 register spill/fill to/from stack in precision tracking")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231209010958.66758-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
generic_map_{delete,update}_batch() doesn't set uattr->batch.count as
zero before it tries to allocate memory for key. If the memory
allocation fails, the value of uattr->batch.count will be incorrect.
Fix it by setting uattr->batch.count as zero beore batched update or
deletion.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231208102355.2628918-6-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When doing batched lookup and deletion operations on htab of maps,
maybe_wait_bpf_programs() is needed to ensure all programs don't use the
inner map after the bpf syscall returns.
Instead of adding the wait in __htab_map_lookup_and_delete_batch(),
adding the wait in bpf_map_do_batch() and also removing the calling of
maybe_wait_bpf_programs() from generic_map_{delete,update}_batch().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231208102355.2628918-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Both map_lookup_elem() and generic_map_lookup_batch() use
bpf_map_copy_value() to lookup and copy the value, and there is no
update operation in bpf_map_copy_value(), so just remove the invocation
of maybe_wait_bpf_programs() from it.
Fixes: 15c14a3dca ("bpf: Add bpf_map_{value_size, update_value, map_copy_value} functions")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231208102355.2628918-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In the current cgroup1 environment, associating operations between cgroups
and applications in a BPF program requires storing a mapping of cgroup_id
to application either in a hash map or maintaining it in userspace.
However, by enabling bpf_cgrp_storage for cgroup1, it becomes possible to
conveniently store application-specific information in cgroup-local storage
and utilize it within BPF programs. Furthermore, enabling this feature for
cgroup1 involves minor modifications for the non-attach case, streamlining
the process.
However, when it comes to enabling this functionality for the cgroup1
attach case, it presents challenges. Therefore, the decision is to focus on
enabling it solely for the cgroup1 non-attach case at present. If
attempting to attach to a cgroup1 fd, the operation will simply fail with
the error code -EBADF.
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20231206115326.4295-2-laoar.shao@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Privileged programs are supposed to be able to read uninitialized stack
memory (ever since 6715df8d5) but, before this patch, these accesses
were permitted inconsistently. In particular, accesses were permitted
above state->allocated_stack, but not below it. In other words, if the
stack was already "large enough", the access was permitted, but
otherwise the access was rejected instead of being allowed to "grow the
stack". This undesired rejection was happening in two places:
- in check_stack_slot_within_bounds()
- in check_stack_range_initialized()
This patch arranges for these accesses to be permitted. A bunch of tests
that were relying on the old rejection had to change; all of them were
changed to add also run unprivileged, in which case the old behavior
persists. One tests couldn't be updated - global_func16 - because it
can't run unprivileged for other reasons.
This patch also fixes the tracking of the stack size for variable-offset
reads. This second fix is bundled in the same commit as the first one
because they're inter-related. Before this patch, writes to the stack
using registers containing a variable offset (as opposed to registers
with fixed, known values) were not properly contributing to the
function's needed stack size. As a result, it was possible for a program
to verify, but then to attempt to read out-of-bounds data at runtime
because a too small stack had been allocated for it.
Each function tracks the size of the stack it needs in
bpf_subprog_info.stack_depth, which is maintained by
update_stack_depth(). For regular memory accesses, check_mem_access()
was calling update_state_depth() but it was passing in only the fixed
part of the offset register, ignoring the variable offset. This was
incorrect; the minimum possible value of that register should be used
instead.
This tracking is now fixed by centralizing the tracking of stack size in
grow_stack_state(), and by lifting the calls to grow_stack_state() to
check_stack_access_within_bounds() as suggested by Andrii. The code is
now simpler and more convincingly tracks the correct maximum stack size.
check_stack_range_initialized() can now rely on enough stack having been
allocated for the access; this helps with the fix for the first issue.
A few tests were changed to also check the stack depth computation. The
one that fails without this patch is verifier_var_off:stack_write_priv_vs_unpriv.
Fixes: 01f810ace9 ("bpf: Allow variable-offset stack access")
Reported-by: Hao Sun <sunhao.th@gmail.com>
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231208032519.260451-3-andreimatei1@gmail.com
Closes: https://lore.kernel.org/bpf/CABWLsev9g8UP_c3a=1qbuZUi20tGoUXoU07FPf-5FLvhOKOY+Q@mail.gmail.com/
Pull tracing fixes from Steven Rostedt:
- Snapshot buffer issues:
1. When instances started allowing latency tracers, it uses a
snapshot buffer (another buffer that is not written to but swapped
with the main buffer that is). The snapshot buffer needs to be the
same size as the main buffer. But when the snapshot buffers were
added to instances, the code to make the snapshot equal to the
main buffer still was only doing it for the main buffer and not
the instances.
2. Need to stop the current tracer when resizing the buffers.
Otherwise there can be a race if the tracer decides to make a
snapshot between resizing the main buffer and the snapshot buffer.
3. When a tracer is "stopped" in disables both the main buffer and
the snapshot buffer. This needs to be done for instances and not
only the main buffer, now that instances also have a snapshot
buffer.
- Buffered event for filtering issues:
When filtering is enabled, because events can be dropped often, it is
quicker to copy the event into a temp buffer and write that into the
main buffer if it is not filtered or just drop the event if it is,
than to write the event into the ring buffer and then try to discard
it. This temp buffer is allocated and needs special synchronization
to do so. But there were some issues with that:
1. When disabling the filter and freeing the buffer, a call to all
CPUs is required to stop each per_cpu usage. But the code called
smp_call_function_many() which does not include the current CPU.
If the task is migrated to another CPU when it enables the CPUs
via smp_call_function_many(), it will not enable the one it is
currently on and this causes issues later on. Use
on_each_cpu_mask() instead, which includes the current CPU.
2.When the allocation of the buffered event fails, it can give a
warning. But the buffered event is just an optimization (it's
still OK to write to the ring buffer and free it). Do not WARN in
this case.
3.The freeing of the buffer event requires synchronization. First a
counter is decremented to zero so that no new uses of it will
happen. Then it sets the buffered event to NULL, and finally it
frees the buffered event. There's a synchronize_rcu() between the
counter decrement and the setting the variable to NULL, but only a
smp_wmb() between that and the freeing of the buffer. It is
theoretically possible that a user missed seeing the decrement,
but will use the buffer after it is free. Another
synchronize_rcu() is needed in place of that smp_wmb().
- ring buffer timestamps on 32 bit machines
The ring buffer timestamp on 32 bit machines has to break the 64 bit
number into multiple values as cmpxchg is required on it, and a 64
bit cmpxchg on 32 bit architectures is very slow. The code use to
just use two 32 bit values and make it a 60 bit timestamp where the
other 4 bits were used as counters for synchronization. It later came
known that the timestamp on 32 bit still need all 64 bits in some
cases. So 3 words were created to handle the 64 bits. But issues
arised with this:
1. The synchronization logic still only compared the counter with
the first two, but not with the third number, so the
synchronization could fail unknowingly.
2. A check on discard of an event could race if an event happened
between the discard and updating one of the counters. The counter
needs to be updated (forcing an absolute timestamp and not to use
a delta) before the actual discard happens.
* tag 'trace-v6.7-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
ring-buffer: Test last update in 32bit version of __rb_time_read()
ring-buffer: Force absolute timestamp on discard of event
tracing: Fix a possible race when disabling buffered events
tracing: Fix a warning when allocating buffered events fails
tracing: Fix incomplete locking when disabling buffered events
tracing: Disable snapshot buffer when stopping instance tracers
tracing: Stop current tracer when resizing buffer
tracing: Always update snapshot buffer size
Pull misc fixes from Andrew Morton:
"31 hotfixes. Ten of these address pre-6.6 issues and are marked
cc:stable. The remainder address post-6.6 issues or aren't considered
serious enough to justify backporting"
* tag 'mm-hotfixes-stable-2023-12-07-18-47' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (31 commits)
mm/madvise: add cond_resched() in madvise_cold_or_pageout_pte_range()
nilfs2: prevent WARNING in nilfs_sufile_set_segment_usage()
mm/hugetlb: have CONFIG_HUGETLB_PAGE select CONFIG_XARRAY_MULTI
scripts/gdb: fix lx-device-list-bus and lx-device-list-class
MAINTAINERS: drop Antti Palosaari
highmem: fix a memory copy problem in memcpy_from_folio
nilfs2: fix missing error check for sb_set_blocksize call
kernel/Kconfig.kexec: drop select of KEXEC for CRASH_DUMP
units: add missing header
drivers/base/cpu: crash data showing should depends on KEXEC_CORE
mm/damon/sysfs-schemes: add timeout for update_schemes_tried_regions
scripts/gdb/tasks: fix lx-ps command error
mm/Kconfig: make userfaultfd a menuconfig
selftests/mm: prevent duplicate runs caused by TEST_GEN_PROGS
mm/damon/core: copy nr_accesses when splitting region
lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly
checkstack: fix printed address
mm/memory_hotplug: fix error handling in add_memory_resource()
mm/memory_hotplug: add missing mem_hotplug_lock
.mailmap: add a new address mapping for Chester Lin
...
