[PATCH] relayfs: remove warning printk() in relay_switch_subbuf() (fd30fc32) · Commits · 戴 / test

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:

Tom Zanussi <zanussi@us.ibm.com> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

fs/relayfs/relay.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -333,8 +333,7 @@ size_t relay_switch_subbuf(struct rchan_buf *buf, size_t length)
		return length;

		toobig:
		printk(KERN_WARNING "relayfs: event too large (%Zd)\n", length);
		WARN_ON(1);
		buf->chan->last_toobig = length;
		return 0;
		}

		@@ -399,6 +398,11 @@ void relay_close(struct rchan *chan)
		relay_close_buf(chan->buf[i]);
		}

		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);
		}

include/linux/relayfs_fs.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -20,9 +20,9 @@
		#include <linux/kref.h>

		/*
		* Tracks changes to rchan_buf struct
		* Tracks changes to rchan/rchan_buf structs
		*/
		#define RELAYFS_CHANNEL_VERSION 5
		#define RELAYFS_CHANNEL_VERSION 6

		/*
		* 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 */
		};

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