From: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
From: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
Also, fix a bit of issues in activate_fd().
It's not up-to-date wrt comment vs. code.
I had this patch in my queue since some time, because it fixes some spinlocks vs
sleeps issues; please verify whether after your restructuring it is still
needed (it applied before this restructuring).
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[EMAIL PROTECTED]>
---
arch/um/kernel/irq.c | 26 +++++++++++++-------------
1 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 589c69a..a5da95f 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -124,7 +124,7 @@ int activate_fd(int irq, int fd, int typ
if (err < 0)
goto out;
- new_fd = um_kmalloc(sizeof(*new_fd));
+ new_fd = um_kmalloc_atomic(sizeof(*new_fd));
err = -ENOMEM;
if (new_fd == NULL)
goto out;
@@ -145,15 +145,17 @@ int activate_fd(int irq, int fd, int typ
/* Critical section - locked by a spinlock because this stuff can
* be changed from interrupt handlers. The stuff above is done
* outside the lock because it allocates memory.
+ * Also, we can be called with spinlocks held - see
+ * write_sigio_workaround->write_sigio_irq->um_request_irq->activate_fd.
*/
/* Actually, it only looks like it can be called from interrupt
* context. The culprit is reactivate_fd, which calls
* maybe_sigio_broken, which calls write_sigio_workaround,
* which calls activate_fd. However, write_sigio_workaround should
- * only be called once, at boot time. That would make it clear that
- * this is called only from process context, and can be locked with
- * a semaphore.
+ * only be called once, at boot time.
+ * However we can be still called (once) under spinlocks, so we need
+ * anyway a semaphore.
*/
spin_lock_irqsave(&irq_lock, flags);
for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
@@ -182,21 +184,19 @@ int activate_fd(int irq, int fd, int typ
* and tmp_fds is NULL or too small for new pollfds array.
* Needed size is equal to n as minimum.
*
- * Here we have to drop the lock in order to call
- * kmalloc, which might sleep.
- * If something else came in and changed the pollfds array
+ * We don't drop the lock any more; when we dropped it, we
+ * needed to loop:
+ * "If something else came in and changed the pollfds array
* so we will not be able to put new pollfd struct to pollfds
- * then we free the buffer tmp_fds and try again.
+ * then we free the buffer tmp_fds and try again."
+ * Do we still need now? Keep on the safe side for now - BB.
*/
- spin_unlock_irqrestore(&irq_lock, flags);
kfree(tmp_pfd);
tmp_pfd = NULL;
- tmp_pfd = um_kmalloc(n);
+ tmp_pfd = um_kmalloc_atomic(n);
if (tmp_pfd == NULL)
- goto out_kfree;
-
- spin_lock_irqsave(&irq_lock, flags);
+ goto out_unlock;
}
/*-------------*/
-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys -- and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
User-mode-linux-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
