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SubjectRe: 2.6.30-rc1 regression? -- epoll: BUG: sleeping function called from invalid context
Davide Libenzi wrote:
> Do you have a chance to give the patch below a spin, in your context?
>
>
>
> - Davide

This works for me, i.e. the previously 100% reliably triggered BUGs went
away, and testing did not reveal any issues anymore.

> ---
> fs/eventpoll.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> Index: linux-2.6.mod/fs/eventpoll.c
> ===================================================================
> --- linux-2.6.mod.orig/fs/eventpoll.c 2009-06-15 19:27:05.000000000 -0700
> +++ linux-2.6.mod/fs/eventpoll.c 2009-06-15 21:14:36.000000000 -0700
> @@ -13,6 +13,7 @@
>
> #include <linux/init.h>
> #include <linux/kernel.h>
> +#include <linux/hardirq.h>
> #include <linux/sched.h>
> #include <linux/fs.h>
> #include <linux/file.h>
> @@ -98,7 +99,7 @@ struct epoll_filefd {
> struct nested_call_node {
> struct list_head llink;
> void *cookie;
> - int cpu;
> + void *ctx;
> };
>
> /*
> @@ -317,17 +318,17 @@ static void ep_nested_calls_init(struct
> * @nproc: Nested call core function pointer.
> * @priv: Opaque data to be passed to the @nproc callback.
> * @cookie: Cookie to be used to identify this nested call.
> + * @ctx: This instance context.
> *
> * Returns: Returns the code returned by the @nproc callback, or -1 if
> * the maximum recursion limit has been exceeded.
> */
> static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
> int (*nproc)(void *, void *, int), void *priv,
> - void *cookie)
> + void *cookie, void *ctx)
> {
> int error, call_nests = 0;
> unsigned long flags;
> - int this_cpu = get_cpu();
> struct list_head *lsthead = &ncalls->tasks_call_list;
> struct nested_call_node *tncur;
> struct nested_call_node tnode;
> @@ -340,7 +341,7 @@ static int ep_call_nested(struct nested_
> * very much limited.
> */
> list_for_each_entry(tncur, lsthead, llink) {
> - if (tncur->cpu == this_cpu &&
> + if (tncur->ctx == ctx &&
> (tncur->cookie == cookie || ++call_nests > max_nests)) {
> /*
> * Ops ... loop detected or maximum nest level reached.
> @@ -352,7 +353,7 @@ static int ep_call_nested(struct nested_
> }
>
> /* Add the current task and cookie to the list */
> - tnode.cpu = this_cpu;
> + tnode.ctx = ctx;
> tnode.cookie = cookie;
> list_add(&tnode.llink, lsthead);
>
> @@ -364,10 +365,9 @@ static int ep_call_nested(struct nested_
> /* Remove the current task from the list */
> spin_lock_irqsave(&ncalls->lock, flags);
> list_del(&tnode.llink);
> - out_unlock:
> +out_unlock:
> spin_unlock_irqrestore(&ncalls->lock, flags);
>
> - put_cpu();
> return error;
> }
>
> @@ -408,8 +408,12 @@ static int ep_poll_wakeup_proc(void *pri
> */
> static void ep_poll_safewake(wait_queue_head_t *wq)
> {
> + int this_cpu = get_cpu();
> +
> ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
> - ep_poll_wakeup_proc, NULL, wq);
> + ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
> +
> + put_cpu();
> }
>
> /*
> @@ -663,7 +667,7 @@ static unsigned int ep_eventpoll_poll(st
> * could re-enter here.
> */
> pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
> - ep_poll_readyevents_proc, ep, ep);
> + ep_poll_readyevents_proc, ep, ep, current);
>
> return pollflags != -1 ? pollflags : 0;
> }

Thanks for the quick response,
--
Stefan Richter
-=====-==--= -==- =----
http://arcgraph.de/sr/


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