From: Petr Mladek <pmladek@suse.com>
To: John Ogness <john.ogness@linutronix.de>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>
Cc: Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Petr Mladek <pmladek@suse.com>
Subject: [PATCH] printk: Enough to disable preemption in printk deferred context
Date: Wed, 19 Apr 2023 09:42:10 +0200 [thread overview]
Message-ID: <20230419074210.17646-1-pmladek@suse.com> (raw)
The comment above printk_deferred_enter()/exit() definition claims
that it can be used only when interrupts are disabled.
It was required by the original printk_safe_log_store() implementation.
The code provided lockless synchronization between a single writer and
a single reader. The interrupt and the normal context shared the same
buffer.
The commit 93d102f094be ("printk: remove safe buffers") removed
these temporary buffers. Instead, the messages are stored directly into
the new global lockless buffer which supports multiple parallel writers.
As a result, it is safe to interrupt one writer now. The preemption still
has to be disabled because the deferred context is CPU specific.
Fixes: 93d102f094be ("printk: remove safe buffers")
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
include/linux/printk.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 8ef499ab3c1e..915a321b491e 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -161,7 +161,7 @@ extern void __printk_safe_enter(void);
extern void __printk_safe_exit(void);
/*
* The printk_deferred_enter/exit macros are available only as a hack for
- * some code paths that need to defer all printk console printing. Interrupts
+ * some code paths that need to defer all printk console printing. Preemption
* must be disabled for the deferred duration.
*/
#define printk_deferred_enter __printk_safe_enter
--
2.35.3
next reply other threads:[~2023-04-19 7:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-19 7:42 Petr Mladek [this message]
2023-04-19 8:23 ` [PATCH] printk: Enough to disable preemption in printk deferred context Sergey Senozhatsky
2023-04-19 8:23 ` Michal Hocko
2023-04-19 10:31 ` Petr Mladek
2023-04-19 9:05 ` John Ogness
2023-04-19 12:03 ` Petr Mladek
2023-04-19 12:14 ` Michal Hocko
2023-04-19 13:45 ` John Ogness
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