Demonstrate use of DECLARE_DYNDBG_CLASSMAP macro, and expose them as
sysfs-nodes for testing.
For each of the 4 class-map-types:
- declare a class-map of that type,
- declare the enum corresponding to those class-names
- share _base across 0..30 range
- add a __pr_debug_cls() call for each class-name
- declare 2 sysnodes for each class-map
for 'p' flag, and future 'T' flag
These declarations create the following sysfs parameter interface:
:#> pwd
/sys/module/test_dynamic_debug/parameters
:#> ls
T_disjoint_bits T_disjoint_names T_level_names T_level_num do_prints
p_disjoint_bits p_disjoint_names p_level_names p_level_num
NOTES:
The local wrapper macro is an api candidate, but there are already too
many parameters. OTOH, maybe related enum should be in there too,
since it has _base inter-dependencies.
The T_* params control the (future) T flag on the same class'd
pr_debug callsites as their p* counterparts. Using them will fail,
until the dyndbg-trace patches are added in.
:#> echo 1 > T_disjoint
[ 28.792489] dyndbg: disjoint: 0x1 > test_dynamic_debug.T_D2
[ 28.793848] dyndbg: query 0: "class D2_CORE +T" mod:*
[ 28.795086] dyndbg: split into words: "class" "D2_CORE" "+T"
[ 28.796467] dyndbg: op='+'
[ 28.797148] dyndbg: unknown flag 'T'
[ 28.798021] dyndbg: flags parse failed
[ 28.798947] dyndbg: processed 1 queries, with 0 matches, 1 errs
[ 28.800378] dyndbg: bit_0: -22 matches on class: D2_CORE -> 0x1
[ 28.801959] dyndbg: test_dynamic_debug.T_D2: updated 0x0 -> 0x1
[ 28.803974] dyndbg: total matches: -22
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-22-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add kernel_param_ops and callbacks to use a class-map to validate and
apply input to a sysfs-node, which allows users to control classes
defined in that class-map. This supports uses like:
echo 0x3 > /sys/module/drm/parameters/debug
IE add these:
- int param_set_dyndbg_classes()
- int param_get_dyndbg_classes()
- struct kernel_param_ops param_ops_dyndbg_classes
Following the model of kernel/params.c STANDARD_PARAM_DEFS, these are
non-static and exported. This might be unnecessary here.
get/set use an augmented kernel_param; the arg refs a new struct
ddebug_class_param, which contains:
- A ptr to user's state-store; a union of &ulong for drm.debug, &int
for nouveau level debug. By ref'g the client's bit-state _var, code
coordinates with existing code (like drm_debug_enabled) which uses
it, so existing/remaining calls can work unchanged. Changing
drm.debug to a ulong allows use of BIT() etc.
- FLAGS: dyndbg.flags toggled by changes to bitmap. Usually just "p".
- MAP: a pointer to struct ddebug_classes_map, which maps those
class-names to .class_ids 0..N that the module is using. This
class-map is declared & initialized by DECLARE_DYNDBG_CLASSMAP.
- map-type: 4 enums DD_CLASS_TYPE_* select 2 input forms and 2 meanings.
numeric input:
DD_CLASS_TYPE_DISJOINT_BITS integer input, independent bits. ie: drm.debug
DD_CLASS_TYPE_LEVEL_NUM integer input, 0..N levels
classnames-list (comma separated) input:
DD_CLASS_TYPE_DISJOINT_NAMES each name affects a bit, others preserved
DD_CLASS_TYPE_LEVEL_NAMES names have level meanings, like kern_levels.h
_NAMES - comma-separated classnames (with optional +-)
_NUM - numeric input, 0-N expected
_BITS - numeric input, 0x1F bitmap form expected
_DISJOINT - bits are independent
_LEVEL - (x<y) on bit-pos.
_DISJOINT treats input like a bit-vector (ala drm.debug), and sets
each bit accordingly. LEVEL is layered on top of this.
_LEVEL treats input like a bit-pos:N, then sets bits(0..N)=1, and
bits(N+1..max)=0. This applies (bit<N) semantics on top of disjoint
bits.
USAGES:
A potentially typical _DISJOINT_NAMES use:
echo +DRM_UT_CORE,+DRM_UT_KMS,-DRM_UT_DRIVER,-DRM_UT_ATOMIC \
> /sys/module/drm/parameters/debug_catnames
A naive _LEVEL_NAMES use, with one class, that sets all in the
class-map according to (x<y):
: problem seen
echo +L7 > /sys/module/test_dynamic_debug/parameters/p_level_names
: problem solved
echo -L1 > /sys/module/test_dynamic_debug/parameters/p_level_names
Note this artifact:
: this is same as prev cmd (due to +/-)
echo L0 > /sys/module/test_dynamic_debug/parameters/p_level_names
: this is "even-more" off, but same wo __pr_debug_class(L0, "..").
echo -L0 > /sys/module/test_dynamic_debug/parameters/p_level_names
A stress-test/make-work usage (kid toggling a light switch):
echo +L7,L0,L7,L0,L7,L0,L7,L0,L7,L0,L7,L0,L7 \
> /sys/module/test_dynamic_debug/parameters/p_level_names
ddebug_apply_class_bitmap(): inside-fn, works on bitmaps, receives
new-bits, finds diffs vs client-bitvector holding "current" state,
and issues exec_query to commit the adjustment.
param_set_dyndbg_classes(): interface fn, sends _NAMES to
param_set_dyndbg_classnames() and returns, falls thru to handle _BITS,
_NUM internally, and calls ddebug_apply_class_bitmap(). Finishes by
updating state.
param_set_dyndbg_classnames(): handles classnames-list in loop, calls
ddebug_apply_class_bitmap for each, then updates state.
NOTES:
_LEVEL_ is overlay on _DISJOINT_; inputs are converted to a bitmask,
by the callbacks. IOW this is possible, and possibly confusing:
echo class V3 +p > control
echo class V1 -p > control
IMO thats ok, relative verbosity is an interface property.
_LEVEL_NUM maps still need class-names, even though the names are not
usable at the sysfs interface (unlike with _NAMES style). The names
are the only way to >control the classes.
- It must have a "V0" name,
something below "V1" to turn "V1" off.
__pr_debug_cls(V0,..) is printk, don't do that.
- "class names" is required at the >control interface.
- relative levels are not enforced at >control
_LEVEL_NAMES bear +/- signs, which alters the on-bit-pos by 1. IOW,
+L2 means L0,L1,L2, and -L2 means just L0,L1. This kinda spoils the
readback fidelity, since the L0 bit gets turned on by any use of any
L*, except "-L0".
All the interface uncertainty here pertains to the _NAMES features.
Nobody has actually asked for this, so its practical (if a little
tedious) to split it out.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-21-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Rework/modernize docs:
- use /proc/dynamic_debug/control in examples
its *always* there (when dyndbg is config'd), even when <debugfs> is not.
drop <debugfs> talk, its a distraction here.
- alias ddcmd='echo $* > /proc/dynamic_debug/control
focus on args: declutter, hide boilerplate, make pwd independent.
- swap sections: Viewing before Controlling. control file as Catalog.
- focus on use by a system administrator
add an alias to make examples more readable
drop grep-101 lessons, admins know this.
- use init/main.c as 1st example, thread it thru doc where useful.
everybodys kernel boots, runs these.
- add *prdbg* api section
to the bottom of the file, its for developers more than admins.
move list of api functions there.
- simplify - drop extra words, phrases, sentences.
- add "decorator" flags line to unify "prefix", trim fmlt descriptions
CC: linux-doc@vger.kernel.org
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-20-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add module-to-class validation:
#> echo class DRM_UT_KMS +p > /proc/dynamic_debug/control
If a query has "class FOO", then ddebug_find_valid_class(), called
from ddebug_change(), requires that FOO is known to module X,
otherwize the query is skipped entirely for X. This protects each
module's class-space, other than the default:31.
The authors' choice of FOO is highly selective, giving isolation
and/or coordinated sharing of FOOs. For example, only DRM modules
should know and respond to DRM_UT_KMS.
So this, combined with module's opt-in declaration of known classes,
effectively privatizes the .class_id space for each module (or
coordinated set of modules).
Notes:
For all "class FOO" queries, ddebug_find_valid_class() is called, it
returns the map matching the query, and sets valid_class via an
*outvar).
If no "class FOO" is supplied, valid_class = _CLASS_DFLT. This
insures that legacy queries do not trample on new class'd callsites,
as they get added.
Also add a new column to control-file output, displaying non-default
class-name (when found) or the "unknown _id:", if it has not been
(correctly) declared with one of the declarator macros.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-18-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add ddebug_attach_module_classes(), call it from ddebug_add_module().
It scans the classes/section its given, finds records where the
module-name matches the module being added, and adds them to the
module's maps list. No locking here, since the record
isn't yet linked into the ddebug_tables list.
It is called indirectly from 2 sources:
- from load_module(), where it scans the module's __dyndbg_classes
section, which contains DYNAMIC_DEBUG_CLASSES definitions from just
the module.
- from dynamic_debug_init(), where all DYNAMIC_DEBUG_CLASSES
definitions of each builtin module have been packed together.
This is why ddebug_attach_module_classes() checks module-name.
NOTES
Its (highly) likely that builtin classes will be ordered by module
name (just like prdbg descriptors are in the __dyndbg section). So
the list can be replaced by a vector (ptr + length), which will work
for loaded modules too. This would imitate whats currently done for
the _ddebug descriptors.
That said, converting to vector,len is close to pointless; a small
minority of modules will ever define a class-map, and almost all of
them will have only 1 or 2 class-maps, so theres only a couple dozen
pointers to save. TODO: re-evaluate for lines removable.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-17-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add __dyndbg_classes section, using __dyndbg as a model. Use it:
vmlinux.lds.h:
KEEP the new section, which also silences orphan section warning on
loadable modules. Add (__start_/__stop_)__dyndbg_classes linker
symbols for the c externs (below).
kernel/module/main.c:
- fill new fields in find_module_sections(), using section_objs()
- extend callchain prototypes
to pass classes, length
load_module(): pass new info to dynamic_debug_setup()
dynamic_debug_setup(): new params, pass through to ddebug_add_module()
dynamic_debug.c:
- add externs to the linker symbols.
ddebug_add_module():
- It currently builds a debug_table, and *will* find and attach classes.
dynamic_debug_init():
- add class fields to the _ddebug_info cursor var: di.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-16-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Using DECLARE_DYNDBG_CLASSMAP, modules can declare up to 31 classnames.
By doing so, they authorize dyndbg to manipulate class'd prdbgs (ie:
__pr_debug_cls, and soon drm_*dbg), ala::
:#> echo class DRM_UT_KMS +p > /proc/dynamic_debug/control
The macro declares and initializes a static struct ddebug_class_map::
- maps approved class-names to class_ids used in module,
by array order. forex: DRM_UT_*
- class-name vals allow validation of "class FOO" queries
using macro is opt-in
- enum class_map_type - determines interface, behavior
Each module has its own class-type and class_id space, and only known
class-names will be authorized for a manipulation. Only DRM modules
should know and respont to this:
:#> echo class DRM_UT_CORE +p > control # across all modules
pr_debugs (with default class_id) are still controllable as before.
DECLARE_DYNDBG_CLASSMAP(_var, _maptype, _base, classes...) is::
_var: name of the static struct var. user passes to module_param_cb()
if they want a sysfs node.
_maptype: this is hard-coded to DD_CLASS_TYPE_DISJOINT_BITS for now.
_base: usually 0, it allows splitting 31 classes into subranges, so
that multiple classes / sysfs-nodes can share the module's
class-id space.
classes: list of class_name strings, these are mapped to class-ids
starting at _base. This class-names list must have a
corresponding ENUM, with SYMBOLS that match the literals,
and 1st enum val = _base.
enum class_map_type has 4 values, on 2 factors::
- classes are disjoint/independent vs relative/x<y/verbosity.
disjoint is basis, verbosity by overlay.
- input NUMBERS vs [+-]CLASS_NAMES
uints, ideally hex. vs +DRM_UT_CORE,-DRM_UT_KMS
DD_CLASS_TYPE_DISJOINT_BITS: classes are separate, one per bit.
expecting hex input. built for drm.debug, basis for other types.
DD_CLASS_TYPE_DISJOINT_NAMES: input is a CSV of [+-]CLASS_NAMES,
classes are independent, like DISJOINT
DD_CLASS_TYPE_LEVEL_NUM: input is numeric level, 0-N.
0 implies silence. use printk to break that.
relative levels applied on bitmaps.
DD_CLASS_TYPE_LEVEL_NAMES: input is a CSV of [+-]CLASS_NAMES,
names like: ERR,WARNING,NOTICE,INFO,DEBUG
avoiding EMERG,ALERT,CRIT,ERR - no point.
NOTES:
The macro places the initialized struct ddebug_class_map into the
__dyndbg_classes section. That draws an 'orphan' warning which we
handle in the next commit. The struct attributes are necessary:
__aligned(8) fixed null-ptr derefs, and __used is needed by drm
drivers, which declare class-maps, but don't also declare a
sysfs-param, and thus dont ref the classmap. The __used insures that
the linkage is made, then the class-map is found at load-time.
While its possible to handle both NAMES and NUMBERS in the same
sys-interface, there is ambiguity to avoid, by disallowing them
together. Later, if ambiguities are resolved, 2 new enums can permit
both inputs, on verbose & independent types separately, and authors
can select the interface style they like.
The plan is to implement LEVELS in the callbacks, outside of
ddebug_exec_query(), which for simplicity will treat the CLASSES in
the map as disjoint. The callbacks can see map-type, and apply ++/--
loops (or bitops) to force the relative meanings across the
class-bitmap.
RFC: That leaves 2 issues:
1. doing LEVELs in callbacks means that the native >control interface
doesn't enforce the LEVELS relationship, so you could confusingly have
V3 enabled, but V1 disabled. OTOH, the control iface already allows
infinite tweaking of the underlying callsites; sysfs node readback can
only tell the user what they previously wrote.
2. All dyndbg >control reduces to a query/command, includes +/-, which
is at-root a kernel patching operation with +/- semantics. And the
_NAMES handling exposes it to the user, making it API-adjacent.
And its not just >control where +/- gets used (which is settled), the
new place is with sysfs-nodes exposing _*_NAMES classes, and here its
subtly different.
_DISJOINT_NAMES: is simple, independent
_LEVEL_NAMES: masks-on bits 0 .. N-1, N..max off
# turn on L3,L2,L1 others off
echo +L3 > /sys/module/test_dynamic_debug/parameters/p_level_names
# turn on L2,L1 others off
echo -L3 > /sys/module/test_dynamic_debug/parameters/p_level_names
IOW, the - changes the threshold-on bitpos by 1.
Alternatively, we could treat the +/- as half-duplex, where -L3 turns
off L>2 (and ignores L1), and +L2 would turn on L<=2 (and ignore others).
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-15-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
For selftest purposes, add __pr_debug_cls(class, fmt, ...)
I didn't think we'd need to define this, since DRM effectively has it
already in drm_dbg, drm_devdbg. But test_dynamic_debug needs it in
order to demonstrate all the moving parts.
Note the __ prefix; its not intended for general use, at least until a
need emerges. ISTM the drm.debug model (macro wrappers inserting enum
const 1st arg) is the baseline approach.
That said, nouveau might want it for easy use in its debug macros. TBD.
NB: it does require a builtin-constant class, __pr_debug_cls(i++, ...)
is disallowed by compiler.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-14-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
DRM issues ~10 exclusive categories of debug messages; to represent
this directly in dyndbg, add a new 6-bit field: struct _ddebug.class_id.
This gives us 64 classes, which should be more than enough.
#> echo 0x012345678 > /sys/module/drm/parameters/debug
All existing callsites are initialized with _DPRINTK_CLASS_DFLT, which
is 2^6-1. This reserves 0-62 for use in new categorized/class'd
pr_debugs, which fits perfectly with natural enums (ints: 0..N).
Thats done by extending the init macro: DEFINE_DYNAMIC_DEBUG_METADATA()
with _CLS(cls, ...) suffix, and redefing old name using extended name.
Then extend the factory macro callchain with _cls() versions to provide
the callsite.class_id, with old-names passing _DPRINTK_CLASS_DFLT.
This sets us up to create class'd prdebug callsites (class'd callsites
are those with .class_id != _DPRINTK_CLASS_DFLT).
No behavior change.
cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-13-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This new struct composes the linker provided (vector,len) section,
and provides a place to add other __dyndbg[] state-data later:
descs - the vector of descriptors in __dyndbg section.
num_descs - length of the data/section.
Use it, in several different ways, as follows:
In lib/dynamic_debug.c:
ddebug_add_module(): Alter params-list, replacing 2 args (array,index)
with a struct _ddebug_info * containing them both, with room for
expansion. This helps future-proof the function prototype against the
looming addition of class-map info into the dyndbg-state, by providing
a place to add more member fields later.
NB: later add static struct _ddebug_info builtins_state declaration,
not needed yet.
ddebug_add_module() is called in 2 contexts:
In dynamic_debug_init(), declare, init a struct _ddebug_info di
auto-var to use as a cursor. Then iterate over the prdbg blocks of
the builtin modules, and update the di cursor before calling
_add_module for each.
Its called from kernel/module/main.c:load_info() for each loaded
module:
In internal.h, alter struct load_info, replacing the dyndbg array,len
fields with an embedded _ddebug_info containing them both; and
populate its members in find_module_sections().
The 2 calling contexts differ in that _init deals with contiguous
subranges of __dyndbgs[] section, packed together, while loadable
modules are added one at a time.
So rename ddebug_add_module() into outer/__inner fns, call __inner
from _init, and provide the offset into the builtin __dyndbgs[] where
the module's prdbgs reside. The cursor provides start, len of the
subrange for each. The offset will be used later to pack the results
of builtin __dyndbg_sites[] de-duplication, and is 0 and unneeded for
loadable modules,
Note:
kernel/module/main.c includes <dynamic_debug.h> for struct
_ddeubg_info. This might be prone to include loops, since its also
included by printk.h. Nothing has broken in robot-land on this.
cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-12-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rework var-names for clarity, regularity
rename variables
- n to mod_sites - it counts sites-per-module
- entries to i - display only
- iter_start to iter_mod_start - marks start of each module's subrange
- modct to mod_ct - stylistic
new iterator var:
- site - cursor parallel to iter
1st step towards 'demotion' of iter->site, for removal later
treat vars as iters:
- drop init at top
init just above for-loop, in a textual block
Acked-by: Jason Baron <jbaron@akamai.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-11-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
dyndbg's control-parser: ddebug_parse_query(), requires that search
terms: module, func, file, lineno, are used only once in a query; a
thing cannot be named both foo and bar.
The cited commit added an overriding module modname, taken from the
module loader, which is authoritative. So it set query.module 1st,
which disallowed its use in the query-string.
But now, its useful to allow a module-load to enable classes across a
whole (or part of) a subsystem at once.
# enable (dynamic-debug in) drm only
modprobe drm dyndbg="class DRM_UT_CORE +p"
# get drm_helper too
modprobe drm dyndbg="class DRM_UT_CORE module drm* +p"
# get everything that knows DRM_UT_CORE
modprobe drm dyndbg="class DRM_UT_CORE module * +p"
# also for boot-args:
drm.dyndbg="class DRM_UT_CORE module * +p"
So convert the override into a default, by filling it only when/after
the query-string omitted the module.
NB: the query class FOO handling is forthcoming.
Fixes: 8e59b5cfb9 dynamic_debug: add modname arg to exec_query callchain
Acked-by: Jason Baron <jbaron@akamai.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-8-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Walk the module's vector of callsites backwards; ie N..0. This
"corrects" the backwards appearance of a module's prdbg vector when
walked 0..N. I think this is due to linker mechanics, which I'm
inclined to treat as immutable, and the order is fixable in display.
No functional changes.
Combined with previous commit, which reversed tables-list, we get:
:#> head -n7 /proc/dynamic_debug/control
# filename:lineno [module]function flags format
init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\012"
init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\012"
init/main.c:1424 [main]run_init_process =_ " with arguments:\012"
init/main.c:1426 [main]run_init_process =_ " %s\012"
init/main.c:1427 [main]run_init_process =_ " with environment:\012"
init/main.c:1429 [main]run_init_process =_ " %s\012"
Acked-by: Jason Baron <jbaron@akamai.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-6-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
For CONFIG_DYNAMIC_DEBUG=N, the ddebug_dyndbg_module_param_cb()
stub-fn is too permissive:
bash-5.1# modprobe drm JUNKdyndbg
bash-5.1# modprobe drm dyndbgJUNK
[ 42.933220] dyndbg param is supported only in CONFIG_DYNAMIC_DEBUG builds
[ 42.937484] ACPI: bus type drm_connector registered
This caused no ill effects, because unknown parameters are either
ignored by default with an "unknown parameter" warning, or ignored
because dyndbg allows its no-effect use on non-dyndbg builds.
But since the code has an explicit feedback message, it should be
issued accurately. Fix with strcmp for exact param-name match.
Fixes: b48420c1d3 dynamic_debug: make dynamic-debug work for module initialization
Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Jason Baron <jbaron@akamai.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-3-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
In https://lore.kernel.org/lkml/20211209150910.GA23668@axis.com/
Vincent's patch commented on, and worked around, a bug toggling
static_branch's, when a 2nd PRINTK-ish flag was added. The bug
results in a premature static_branch_disable when the 1st of 2 flags
was disabled.
The cited commit computed newflags, but then in the JUMP_LABEL block,
failed to use that result, instead using just one of the terms in it.
Using newflags instead made the code work properly.
This is Vincents test-case, reduced. It needs the 2nd flag to
demonstrate the bug, but it's explanatory here.
pt_test() {
echo 5 > /sys/module/dynamic_debug/verbose
site="module tcp" # just one callsite
echo " $site =_ " > /proc/dynamic_debug/control # clear it
# A B ~A ~B
for flg in +T +p "-T #broke here" -p; do
echo " $site $flg " > /proc/dynamic_debug/control
done;
# A B ~B ~A
for flg in +T +p "-p #broke here" -T; do
echo " $site $flg " > /proc/dynamic_debug/control
done
}
pt_test
Fixes: 84da83a6ff dyndbg: combine flags & mask into a struct, simplify with it
CC: vincent.whitchurch@axis.com
Acked-by: Jason Baron <jbaron@akamai.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20220904214134.408619-2-jim.cromie@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If the gfp flag used for the memory allocation already has __GFP_ZERO,
then there is no need to explicitly clear the "struct devres_node". It is
already zeroed.
This saves a few cycles when using devm_zalloc() and co.
In the case of devres_alloc() (which calls __devres_alloc_node()), the
compiler could remove the test and the memset() because it should be able
to see that the __GFP_ZERO flag is set.
So this would make the code both faster and smaller.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/d255bd871484e63cdd628e819f929e2df59afb02.1658352383.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Salvatore Bonaccorso
Jim Cromie
Christophe JAILLET
Brian Norris
Yang Yingliang