Commit fd30fc32 authored by Tom Zanussi's avatar Tom Zanussi Committed by Linus Torvalds

[PATCH] relayfs: remove warning printk() in relay_switch_subbuf()

There's currently a diagnostic printk in relay_switch_subbuf() meant as
a warning if you accidentally try to log an event larger than the
sub-buffer size.

The problem is if this happens while logging from somewhere it's not
safe to be doing printks, such as in the scheduler, you can end up with
a deadlock.  This patch removes the warning from relay_switch_subbuf()
and instead prints some diagnostic info when the channel is closed.

Thanks to Mathieu Desnoyers for pointing out the problem and
suggesting a fix.
Signed-off-by: default avatarTom Zanussi <>
Signed-off-by: default avatarLinus Torvalds <>
parent bb44f116
......@@ -333,8 +333,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
return length;
printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length);
buf->chan->last_toobig = length;
return 0;
......@@ -399,6 +398,11 @@ void relay_close(struct rchan *chan)
if (chan->last_toobig)
printk(KERN_WARNING "relayfs: one or more items not logged "
"[item size (%Zd) > sub-buffer size (%Zd)]\n",
chan->last_toobig, chan->subbuf_size);
kref_put(&chan->kref, relay_destroy_channel);
......@@ -20,9 +20,9 @@
#include <linux/kref.h>
* Tracks changes to rchan_buf struct
* Tracks changes to rchan/rchan_buf structs
* Per-cpu relay channel buffer
......@@ -60,6 +60,7 @@ struct rchan
struct rchan_callbacks *cb; /* client callbacks */
struct kref kref; /* channel refcount */
void *private_data; /* for user-defined data */
size_t last_toobig; /* tried to log event > subbuf size */
struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment