Accessing task->comm requires proper locking. However in the past
access to current->comm could be done without locking. This
is no longer the case, so all comm access needs to be done
while holding the comm_lock.
In my attempt to clean up unprotected comm access, I've noticed
most comm access is done for printk output. To simplify correct
locking in these cases, I've introduced a new %ptc format,
which will print the corresponding task's comm.
Example use:
printk("%ptc: unaligned epc - sending SIGBUS.\n", current);
CC: Joe Perches <joe@xxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxx>
CC: Michal Nazarewicz <mina86@xxxxxxxxxx>
CC: Andy Whitcroft <apw@xxxxxxxxxxxxx>
CC: Jiri Slaby <jirislaby@xxxxxxxxx>
CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
CC: David Rientjes <rientjes@xxxxxxxxxx>
CC: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: linux-mm@xxxxxxxxx
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
lib/vsprintf.c | 24 ++++++++++++++++++++++++
1 files changed, 24 insertions(+), 0 deletions(-)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index bc0ac6b..b7a9953 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -797,6 +797,23 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
return string(buf, end, uuid, spec);
}
+static noinline_for_stack
+char *task_comm_string(char *buf, char *end, void *addr,
+ struct printf_spec spec, const char *fmt)
+{
+ struct task_struct *tsk = addr;
+ char *ret;
+ unsigned long flags;
+
+ spin_lock_irqsave(&tsk->comm_lock, flags);
+ ret = string(buf, end, tsk->comm, spec);
+ spin_unlock_irqrestore(&tsk->comm_lock, flags);
+
+ return ret;
+}
+
+
+
int kptr_restrict = 1;
/*
@@ -864,6 +881,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
}
switch (*fmt) {
+ case 't':
+ switch (fmt[1]) {
+ case 'c':
+ return task_comm_string(buf, end, ptr, spec, fmt);
+ }
+ break;
case 'F':
case 'f':
ptr = dereference_function_descriptor(ptr);
@@ -1151,6 +1174,7 @@ qualifier:
* http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-00
* %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper
* case.
+ * %ptc outputs the task's comm name
* %n is ignored
*
* The return value is the number of characters which would
--
1.7.3.2.146.gca209
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>