GitHub-Mirror/linux-bl808
2
0
Fork 0
mirror of https://github.com/Fishwaldo/linux-bl808.git synced 2025-06-17 20:25:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

[PATCH] aio: remove aio_max_nr accounting race

Browse source 
AIO was adding a new context's max requests to the global total before
testing if that resulting total was over the global limit.  This let
innocent tasks get their new limit tested along with a racing guilty task
that was crossing the limit.  This serializes the _nr accounting with a
spinlock It also switches to using unsigned long for the global totals.
Individual contexts are still limited to an unsigned int's worth of
requests by the syscall interface.

The problem and fix were verified with a simple program that spun creating
and destroying a context while holding on to another long lived context.
Before the patch a task creating a tiny context could get a spurious EAGAIN
if it raced with a task creating a very large context that overran the
limit.

Signed-off-by: Zach Brown <zach.brown@oracle.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Zach Brown 2005-11-07 00:59:31 -08:00 • committed by Linus Torvalds
parent 0f6ed7c264
commit d55b5fdaf4
3 changed files with 26 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

5
include/linux/aio.h
View file

@ -183,6 +183,7 @@ struct kioctx {
struct list_head active_reqs; /* used for cancellation */
struct list_head run_list; /* used for kicked reqs */
/* sys_io_setup currently limits this to an unsigned int */
unsigned max_reqs;
struct aio_ring_info ring_info;
@ -234,7 +235,7 @@ static inline struct kiocb *list_kiocb(struct list_head *h)
}
/* for sysctl: */
extern atomic_t aio_nr;
extern unsigned aio_max_nr;
extern unsigned long aio_nr;
extern unsigned long aio_max_nr;
#endif /* __LINUX__AIO_H */