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authorJohn Ogness <john.ogness@linutronix.de>2022-11-16 19:21:22 +0300
committerPetr Mladek <pmladek@suse.com>2022-12-02 13:25:00 +0300
commit8b5dd40088f7a3d85e6072f027ec50f309f64876 (patch)
tree91dc7785c11e00f57197aedd4f0ec46b6d995a45 /fs/proc
parentd25a2e748ae159e43d40f4bc0a9e89cc443e325f (diff)
downloadlinux-8b5dd40088f7a3d85e6072f027ec50f309f64876.tar.xz
proc: consoles: document console_lock usage
The console_lock is held throughout the start/show/stop procedure to print out device/driver information about all registered consoles. Since the console_lock is being used for multiple reasons, explicitly document these reasons. This will be useful when the console_lock is split into fine-grained locking. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20221116162152.193147-11-john.ogness@linutronix.de
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/consoles.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/proc/consoles.c b/fs/proc/consoles.c
index cf2e0788f9c7..46b305fa04ed 100644
--- a/fs/proc/consoles.c
+++ b/fs/proc/consoles.c
@@ -63,6 +63,15 @@ static void *c_start(struct seq_file *m, loff_t *pos)
struct console *con;
loff_t off = 0;
+ /*
+ * Take console_lock to serialize device() callback with
+ * other console operations. For example, fg_console is
+ * modified under console_lock when switching vt.
+ *
+ * Hold the console_lock to guarantee safe traversal of the
+ * console list. SRCU cannot be used because there is no
+ * place to store the SRCU cookie.
+ */
console_lock();
for_each_console(con)
if (off++ == *pos)