| Message ID | 57daf43c5270f7532b269b9f0e90d126ca012354.1705331453.git.sreenath.vijayan@sony.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3,1/2] printk: Add function to dump printk buffer directly to consoles | expand |
On 2024-01-17, Sreenath Vijayan <sreenath.vijayan@sony.com> wrote: > When terminal is unresponsive, one cannot use dmesg to view printk > ring buffer messages. Also, syslog services may be disabled, > to check the messages after a reboot, especially on embedded systems. > In this scenario, dump the printk ring buffer messages via sysrq > by pressing sysrq+D. Note that using sysrq+g with kgdb or kdb it is already possible to dump the printk ringbuffer messages. However using this new sysrq+D is much more comfortable, less intrusive, and generally safer. I have no problems with this change. But I guess the tty maintainers will need to speak up about extending the sysrq list. John
From: Sreenath Vijayan > Sent: 17 January 2024 11:14 .... > /* Key Operations table and lock */ > static DEFINE_SPINLOCK(sysrq_key_table_lock); > > @@ -505,7 +523,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = { > NULL, /* A */ > NULL, /* B */ > NULL, /* C */ > - NULL, /* D */ > + &sysrq_dmesg_dump_op, /* D */ > NULL, /* E */ > NULL, /* F */ > NULL, /* G */ That looks like it ought to use C99 initialisers: ['D' - 'A'] = &sysrq_dmesg_dump_op, Possible with a #define to hide the offset. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
On Thu, Jan 18, 2024 at 10:56:59PM +0000, David Laight wrote: > From: Sreenath Vijayan > > Sent: 17 January 2024 11:14 > .... > > /* Key Operations table and lock */ > > static DEFINE_SPINLOCK(sysrq_key_table_lock); > > > > @@ -505,7 +523,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = { > > NULL, /* A */ > > NULL, /* B */ > > NULL, /* C */ > > - NULL, /* D */ > > + &sysrq_dmesg_dump_op, /* D */ > > NULL, /* E */ > > NULL, /* F */ > > NULL, /* G */ > > That looks like it ought to use C99 initialisers: > ['D' - 'A'] = &sysrq_dmesg_dump_op, > > Possible with a #define to hide the offset. Maybe in the future, but for now, let's leave it as-is please. thanks, greg k-h
diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst index 51906e47327b..246a7b61a0eb 100644 --- a/Documentation/admin-guide/sysrq.rst +++ b/Documentation/admin-guide/sysrq.rst @@ -152,6 +152,8 @@ Command Function will be printed to your console. (``0``, for example would make it so that only emergency messages like PANICs or OOPSes would make it to your console.) + +``D`` Dump the printk ring buffer =========== =================================================================== Okay, so what can I use them for? diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 6b4a28bcf2f5..1976412706a4 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -450,6 +450,24 @@ static const struct sysrq_key_op sysrq_unrt_op = { .enable_mask = SYSRQ_ENABLE_RTNICE, }; +static void dmesg_dump_callback(struct work_struct *work) +{ + dump_printk_buffer(); +} + +static DECLARE_WORK(sysrq_dmesg_work, dmesg_dump_callback); + +static void sysrq_handle_dmesg_dump(u8 key) +{ + queue_work(system_unbound_wq, &sysrq_dmesg_work); +} +static struct sysrq_key_op sysrq_dmesg_dump_op = { + .handler = sysrq_handle_dmesg_dump, + .help_msg = "dump-dmesg(D)", + .action_msg = "Dump dmesg", + .enable_mask = SYSRQ_ENABLE_DUMP, +}; + /* Key Operations table and lock */ static DEFINE_SPINLOCK(sysrq_key_table_lock); @@ -505,7 +523,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = { NULL, /* A */ NULL, /* B */ NULL, /* C */ - NULL, /* D */ + &sysrq_dmesg_dump_op, /* D */ NULL, /* E */ NULL, /* F */ NULL, /* G */