Messages in this thread Patch in this message | | | From | John Stultz <> | Subject | [PATCH 3/4] printk: Add %ptc to safely print a task's comm | Date | Tue, 17 May 2011 18:41:04 -0700 |
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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@perches.com> CC: Ingo Molnar <mingo@elte.hu> CC: Michal Nazarewicz <mina86@mina86.com> CC: Andy Whitcroft <apw@canonical.com> CC: Jiri Slaby <jirislaby@gmail.com> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> CC: David Rientjes <rientjes@google.com> CC: Dave Hansen <dave@linux.vnet.ibm.com> CC: Andrew Morton <akpm@linux-foundation.org> CC: linux-mm@kvack.org Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: John Stultz <john.stultz@linaro.org> --- 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
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