linux/kernel/printk
John Ogness b371cbb584 printk: convert @syslog_lock to mutex
@syslog_lock was a raw_spin_lock to simplify the transition of
removing @logbuf_lock and the safe buffers. With that transition
complete, and since all uses of @syslog_lock are within sleepable
contexts, @syslog_lock can become a mutex.

Note that until now register_console() would disable interrupts
using irqsave, which implies that it may be called with interrupts
disabled. And indeed, there is one possible call chain on parisc
where this happens:

handle_interruption(code=1) /* High-priority machine check (HPMC) */
  pdc_console_restart()
    pdc_console_init_force()
      register_console()

However, register_console() calls console_lock(), which might sleep.
So it has never been allowed to call register_console() from an
atomic context and the above call chain is a bug.

Note that the removal of read_syslog_seq_irq() is slightly changing
the behavior of SYSLOG_ACTION_READ by testing against a possibly
outdated @seq value. However, the value of @seq could have changed
after the test, so it is not a new window. A follow-up commit closes
this window.

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/20210715193359.25946-6-john.ogness@linutronix.de
2021-07-26 15:09:50 +02:00
..
braille.c printk: Replace strncmp() with str_has_prefix() 2019-08-16 09:54:08 +02:00
braille.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
console_cmdline.h printk: Fix preferred console selection with multiple matches 2020-02-18 09:34:42 +01:00
internal.h printk: remove NMI tracking 2021-07-26 15:09:44 +02:00
Makefile printk: add lockless ringbuffer 2020-07-10 08:48:19 +02:00
printk_ringbuffer.c Merge branch 'printk-rework' into for-linus 2021-01-21 16:06:21 +01:00
printk_ringbuffer.h printk: rectify kernel-doc for prb_rec_init_wr() 2021-01-26 11:17:51 +01:00
printk_safe.c printk: remove NMI tracking 2021-07-26 15:09:44 +02:00
printk.c printk: convert @syslog_lock to mutex 2021-07-26 15:09:50 +02:00