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SUNRPC: have svc_recv() check kthread_should_stop() 

When using kthreads that call into svc_recv, we want to make sure that
they do not block there for a long time when we're trying to take down
the kthread.

This patch changes svc_recv() to check kthread_should_stop() at the same
places that it checks to see if it's signalled(). Also check just before
svc_recv() tries to schedule(). By making sure that we check it just
after setting the task state we can avoid having to use any locking or
signalling to ensure it doesn't block for a long time.

There's still a chance of a 500ms sleep if alloc_page() fails, but
that should be a rare occurrence and isn't a terribly long time in
the context of a kthread being taken down.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
This commit is contained in:
Jeff Layton 2008-02-07 16:34:54 -05:00 committed by J. Bruce Fields
parent 23d42ee278
commit 7086721f9c
1 changed files with 22 additions and 2 deletions
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24
net/sunrpc/svc_xprt.c
View File

@ -18,6 +18,7 @@
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <net/sock.h>
#include <net/checksum.h>
#include <net/ip.h>
@ -587,6 +588,8 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
struct page *p = alloc_page(GFP_KERNEL);
if (!p) {
int j = msecs_to_jiffies(500);
if (kthread_should_stop())
return -EINTR;
schedule_timeout_uninterruptible(j);
}
rqstp->rq_pages[i] = p;
@ -607,7 +610,7 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
try_to_freeze();
cond_resched();
if (signalled())
if (signalled() || kthread_should_stop())
return -EINTR;
spin_lock_bh(&pool->sp_lock);
@ -626,6 +629,20 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
* to bring down the daemons ...
*/
set_current_state(TASK_INTERRUPTIBLE);
/*
* checking kthread_should_stop() here allows us to avoid
* locking and signalling when stopping kthreads that call
* svc_recv. If the thread has already been woken up, then
* we can exit here without sleeping. If not, then it
* it'll be woken up quickly during the schedule_timeout
*/
if (kthread_should_stop()) {
set_current_state(TASK_RUNNING);
spin_unlock_bh(&pool->sp_lock);
return -EINTR;
}
add_wait_queue(&rqstp->rq_wait, &wait);
spin_unlock_bh(&pool->sp_lock);
@ -641,7 +658,10 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
svc_thread_dequeue(pool, rqstp);
spin_unlock_bh(&pool->sp_lock);
dprintk("svc: server %p, no data yet\n", rqstp);
return signalled()? -EINTR : -EAGAIN;
if (signalled() || kthread_should_stop())
return -EINTR;
else
return -EAGAIN;
}
}
spin_unlock_bh(&pool->sp_lock);