Re: [PATCH 20/30] panic: Add the panic informational notifier list
On Wed, Apr 27, 2022 at 07:49:14PM -0300, Guilherme G. Piccoli wrote:
> The goal of this new panic notifier is to allow its users to
> register callbacks to run earlier in the panic path than they
> currently do. This aims at informational mechanisms, like dumping
> kernel offsets and showing device error data (in case it's simple
> registers reading, for example) as well as mechanisms to disable
> log flooding (like hung_task detector / RCU warnings) and the
> tracing dump_on_oops (when enabled).
>
> Any (non-invasive) information that should be provided before
> kmsg_dump() as well as log flooding preventing code should fit
> here, as long it offers relatively low risk for kdump.
>
> For now, the patch is almost a no-op, although it changes a bit
> the ordering in which some panic notifiers are executed - specially
> affected by this are the notifiers responsible for disabling the
> hung_task detector / RCU warnings, which now run first. In a
> subsequent patch, the panic path will be refactored, then the
> panic informational notifiers will effectively run earlier,
> before ksmg_dump() (and usually before kdump as well).
>
> We also defer documenting it all properly in the subsequent
> refactor patch. Finally, while at it, we removed some useless
> header inclusions too.
>
> Cc: Benjamin Herrenschmidt
> Cc: Catalin Marinas
> Cc: Florian Fainelli
> Cc: Frederic Weisbecker
> Cc: "H. Peter Anvin"
> Cc: Hari Bathini
> Cc: Joel Fernandes
> Cc: Jonathan Hunter
> Cc: Josh Triplett
> Cc: Lai Jiangshan
> Cc: Leo Yan
> Cc: Mathieu Desnoyers
> Cc: Mathieu Poirier
> Cc: Michael Ellerman
> Cc: Mike Leach
> Cc: Mikko Perttunen
> Cc: Neeraj Upadhyay
> Cc: Nicholas Piggin
> Cc: Paul Mackerras
> Cc: Suzuki K Poulose
> Cc: Thierry Reding
> Cc: Thomas Bogendoerfer
> Signed-off-by: Guilherme G. Piccoli
>From an RCU perspective:
Acked-by: Paul E. McKenney
> ---
> arch/arm64/kernel/setup.c | 2 +-
> arch/mips/kernel/relocate.c | 2 +-
> arch/powerpc/kernel/setup-common.c| 2 +-
> arch/x86/kernel/setup.c | 2 +-
> drivers/bus/brcmstb_gisb.c| 2 +-
> drivers/hwtracing/coresight/coresight-cpu-debug.c | 4 ++--
> drivers/soc/tegra/ari-tegra186.c | 3 ++-
> include/linux/panic_notifier.h| 1 +
> kernel/hung_task.c| 3 ++-
> kernel/panic.c| 4
> kernel/rcu/tree.c | 1 -
> kernel/rcu/tree_stall.h | 3 ++-
> kernel/trace/trace.c | 2 +-
> 13 files changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 3505789cf4bd..ac2c7e8c9c6a 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -444,7 +444,7 @@ static struct notifier_block arm64_panic_block = {
>
> static int __init register_arm64_panic_block(void)
> {
> - atomic_notifier_chain_register(_notifier_list,
> + atomic_notifier_chain_register(_info_list,
> _panic_block);
> return 0;
> }
> diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
> index 56b51de2dc51..650811f2436a 100644
> --- a/arch/mips/kernel/relocate.c
> +++ b/arch/mips/kernel/relocate.c
> @@ -459,7 +459,7 @@ static struct notifier_block kernel_location_notifier = {
>
> static int __init register_kernel_offset_dumper(void)
> {
> - atomic_notifier_chain_register(_notifier_list,
> + atomic_notifier_chain_register(_info_list,
> _location_notifier);
> return 0;
> }
> diff --git a/arch/powerpc/kernel/setup-common.c
> b/arch/powerpc/kernel/setup-common.c
> index 1468c3937bf4..d04b8bf8dbc7 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -757,7 +757,7 @@ void __init setup_panic(void)
> _fadump_block);
>
> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0)
> - atomic_notifier_chain_register(_notifier_list,
> + atomic_notifier_chain_register(_info_list,
> _offset_notifier);
>
> /* Low-level platform-specific routines that should run on panic */
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index c95b9ac5a457..599b25346964 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1266,7 +1266,7 @@ static struct not
Re: [PATCH v3 2/3] printk: add lockless ringbuffer
On Thu, Jun 18, 2020 at 04:55:18PM +0206, John Ogness wrote: > Introduce a multi-reader multi-writer lockless ringbuffer for storing > the kernel log messages. Readers and writers may use their API from > any context (including scheduler and NMI). This ringbuffer will make > it possible to decouple printk() callers from any context, locking, > or console constraints. It also makes it possible for readers to have > full access to the ringbuffer contents at any time and context (for > example from any panic situation). > > The printk_ringbuffer is made up of 3 internal ringbuffers: > > desc_ring: > A ring of descriptors. A descriptor contains all record meta data > (sequence number, timestamp, loglevel, etc.) as well as internal state > information about the record and logical positions specifying where in > the other ringbuffers the text and dictionary strings are located. > > text_data_ring: > A ring of data blocks. A data block consists of an unsigned long > integer (ID) that maps to a desc_ring index followed by the text > string of the record. > > dict_data_ring: > A ring of data blocks. A data block consists of an unsigned long > integer (ID) that maps to a desc_ring index followed by the dictionary > string of the record. > > The internal state information of a descriptor is the key element to > allow readers and writers to locklessly synchronize access to the data. > > Co-developed-by: Petr Mladek > Signed-off-by: John Ogness The orderings match the comments, although a number could (later!) be weakened to the easier-to-read smp_load_acquire() and/or smp_store_release(). So, from a memory-ordering perspective: Reviewed-by: Paul E. McKenney > --- > kernel/printk/Makefile|1 + > kernel/printk/printk_ringbuffer.c | 1674 + > kernel/printk/printk_ringbuffer.h | 352 ++ > 3 files changed, 2027 insertions(+) > create mode 100644 kernel/printk/printk_ringbuffer.c > create mode 100644 kernel/printk/printk_ringbuffer.h > > diff --git a/kernel/printk/Makefile b/kernel/printk/Makefile > index 4d052fc6bcde..eee3dc9b60a9 100644 > --- a/kernel/printk/Makefile > +++ b/kernel/printk/Makefile > @@ -2,3 +2,4 @@ > obj-y= printk.o > obj-$(CONFIG_PRINTK) += printk_safe.o > obj-$(CONFIG_A11Y_BRAILLE_CONSOLE) += braille.o > +obj-$(CONFIG_PRINTK) += printk_ringbuffer.o > diff --git a/kernel/printk/printk_ringbuffer.c > b/kernel/printk/printk_ringbuffer.c > new file mode 100644 > index ..75d056436cc5 > --- /dev/null > +++ b/kernel/printk/printk_ringbuffer.c > @@ -0,0 +1,1674 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include > +#include > +#include > +#include > +#include > +#include "printk_ringbuffer.h" > + > +/** > + * DOC: printk_ringbuffer overview > + * > + * Data Structure > + * -- > + * The printk_ringbuffer is made up of 3 internal ringbuffers: > + * > + * desc_ring > + * A ring of descriptors. A descriptor contains all record meta data > + * (sequence number, timestamp, loglevel, etc.) as well as internal state > + * information about the record and logical positions specifying where in > + * the other ringbuffers the text and dictionary strings are located. > + * > + * text_data_ring > + * A ring of data blocks. A data block consists of an unsigned long > + * integer (ID) that maps to a desc_ring index followed by the text > + * string of the record. > + * > + * dict_data_ring > + * A ring of data blocks. A data block consists of an unsigned long > + * integer (ID) that maps to a desc_ring index followed by the dictionary > + * string of the record. > + * > + * The internal state information of a descriptor is the key element to allow > + * readers and writers to locklessly synchronize access to the data. > + * > + * Implementation > + * -- > + * > + * Descriptor Ring > + * ~~~ > + * The descriptor ring is an array of descriptors. A descriptor contains all > + * the meta data of a printk record as well as blk_lpos structs pointing to > + * associated text and dictionary data blocks (see "Data Rings" below). Each > + * descriptor is assigned an ID that maps directly to index values of the > + * descriptor array and has a state. The ID and the state are bitwise > combined > + * into a single descriptor field named @state_var, allowing ID and state to > + * be synchronously and atomically updated. > + * > + * Descriptors have three states: > + * > + * reserved > + * A writer is modifying the record. > + * > + * committed > + * The record and all its data are complete and av
[PATCH] powerpc: Fix kexec-related UP build error
Hello!
The following patch fixes a UP build problem for kexec() on powerpc.
When the crash_kexec_wait_realmode() function was added, it was
placed in only two of the three required locations.
Thoughts?
Thanx, Paul
The function crash_kexec_wait_realmode() is defined only if SMP, but is
called in UP builds. Create an empty function to keep the compiler happy
in UP builds.
Signed-off-by: Paul E. McKenney paul.mcken...@linaro.org
Signed-off-by: Paul E. McKenney paul...@linux.vnet.ibm.com
diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c
index 3d3d416..6f964ef 100644
--- a/arch/powerpc/kernel/crash.c
+++ b/arch/powerpc/kernel/crash.c
@@ -251,6 +251,10 @@ static void crash_kexec_prepare_cpus(int cpu)
#endif
}
+static void crash_kexec_wait_realmode(int cpu)
+{
+}
+
void crash_kexec_secondary(struct pt_regs *regs)
{
cpus_in_sr = CPU_MASK_NONE;
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Re: [PATCH] powerpc: Fix kexec-related UP build error
On Fri, Apr 15, 2011 at 02:00:51PM -0700, Nishanth Aravamudan wrote: Hi Paul, On 15.04.2011 [13:29:16 -0700], Paul E. McKenney wrote: Hello! The following patch fixes a UP build problem for kexec() on powerpc. When the crash_kexec_wait_realmode() function was added, it was placed in only two of the three required locations. I believe the fix has already been posted as http://lists.ozlabs.org/pipermail/linuxppc-dev/2011-April/089559.html So it has! Thank you for the pointer. Thanx, Paul ___ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
