On Thu 2021-02-25 21:24:35, John Ogness wrote:
quoted hunk ↗ jump to hunk
Rather than storing the iterator information in the registered
kmsg_dumper structure, create a separate iterator structure. The
kmsg_dump_iter structure can reside on the stack of the caller, thus
allowing lockless use of the kmsg_dump functions.
This change also means that the kmsg_dumper dump() callback no
longer needs to pass in the kmsg_dumper as an argument. If
kmsg_dumpers want to access the kernel logs, they can use the new
iterator.
Update the kmsg_dumper callback prototype. Update code that accesses
the kernel logs using the kmsg_dumper structure to use the new
kmsg_dump_iter structure. For kmsg_dumpers, this also means adding a
call to kmsg_dump_rewind() to initialize the iterator.
All this is in preparation for removal of @logbuf_lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
arch/powerpc/kernel/nvram_64.c | 14 +++---
arch/powerpc/platforms/powernv/opal-kmsg.c | 3 +-
arch/powerpc/xmon/xmon.c | 6 +--
arch/um/kernel/kmsg_dump.c | 8 +--
drivers/hv/vmbus_drv.c | 7 +--
drivers/mtd/mtdoops.c | 8 +--
fs/pstore/platform.c | 8 +--
include/linux/kmsg_dump.h | 38 ++++++++-------
kernel/debug/kdb/kdb_main.c | 10 ++--
kernel/printk/printk.c | 57 ++++++++++------------
10 files changed, 81 insertions(+), 78 deletions(-)
diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
index 532f22637783..5a64b24a91c2 100644
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -72,8 +72,7 @@ static const char *nvram_os_partitions[] = {
NULL
};
-static void oops_to_nvram(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason);
+static void oops_to_nvram(enum kmsg_dump_reason reason);
static struct kmsg_dumper nvram_kmsg_dumper = {
.dump = oops_to_nvram@@ -642,11 +641,11 @@ void __init nvram_init_oops_partition(int rtas_partition_exists)
* that we think will compress sufficiently to fit in the lnx,oops-log
* partition. If that's too much, go back and capture uncompressed text.
*/
-static void oops_to_nvram(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason)
+static void oops_to_nvram(enum kmsg_dump_reason reason)
{
struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
static unsigned int oops_count = 0;
+ static struct kmsg_dump_iter iter;
static bool panicking = false;
static DEFINE_SPINLOCK(lock);
unsigned long flags;@@ -681,13 +680,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
return;
if (big_oops_buf) {
- kmsg_dump_get_buffer(dumper, false,
+ kmsg_dump_rewind(&iter);
It would be nice to get rid of the kmsg_dump_rewind(&iter) calls
in all callers.
A solution might be to create the following in include/linux/kmsg_dump.h
#define KMSG_DUMP_ITER_INIT(iter) { \
.cur_seq = 0, \
.next_seq = U64_MAX, \
}
#define DEFINE_KMSG_DUMP_ITER(iter) \
struct kmsg_dump_iter iter = KMSG_DUMP_ITER_INIT(iter)
Then we could do the following at the beginning of both
kmsg_dump_get_buffer() and kmsg_dump_get_line():
u64 clear_seq = latched_seq_read_nolock(&clear_seq);
if (iter->cur_seq < clear_seq)
cur_seq = clear_seq;
I am not completely sure about next_seq:
+ kmsg_dump_get_buffer() will set it for the next call anyway.
It reads the blocks of messages from the newest.
+ kmsg_dump_get_line() wants to read the entire buffer anyway.
But there is a small risk of an infinite loop when new messages
are printed when dumping each line.
It might be better to avoid the infinite loop. We could do the following:
static void check_and_set_iter(struct kmsg_dump_iter)
{
if (iter->cur_seq == 0 && iter->next_seq == U64_MAX) {
kmsg_dump_rewind(iter);
}
and call this at the beginning of both kmsg_dump_get_buffer()
and kmsg_dump_get_line()
What do you think?
Note that I do not resist on it. But it might make the API easier to
use from my POV.
Otherwise the patch looks good to me.
Best Regards,
Petr