Fix select on /proc files without ->poll

Taneli Vähäkangas <[email protected]> reported that commit 786d7e1 aka "Fix rmmod/read/write races in /proc entries" broke SBCL + SLIME combo. The old code in do_select() used DEFAULT_POLLMASK, if couldn't find ->poll handler. The new code makes ->poll always there and returns 0 by default, which is not correct. Return DEFAULT_POLLMASK instead. Steps to reproduce: install emacs, SBCL, SLIME emacs M-x slime in *inferior-lisp* buffer [watch it doing "Connecting to Swank on port X.."] Please, apply before 2.6.23. P.S.: why SBCL can't just read(2) /proc/cpuinfo is a mystery. Signed-off-by: Alexey Dobriyan <[email protected]> Cc: T Taneli Vahakangas <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · Sep 12, 2007 · dd23aae · dd23aae
1 parent 3210f0e
commit dd23aae
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Showing 3 changed files with 4 additions and 3 deletions.
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
@@ -11,6 +11,7 @@
 #include <linux/string.h>
 #include <linux/stat.h>
 #include <linux/completion.h>
+#include <linux/poll.h>
 #include <linux/file.h>
 #include <linux/limits.h>
 #include <linux/init.h>
@@ -232,7 +233,7 @@ static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t
 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 {
 	struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
-	unsigned int rv = 0;
+	unsigned int rv = DEFAULT_POLLMASK;
 	unsigned int (*poll)(struct file *, struct poll_table_struct *);
 
 	spin_lock(&pde->pde_unload_lock);

diff --git a/fs/select.c b/fs/select.c
@@ -26,8 +26,6 @@
 
 #include <asm/uaccess.h>
 
-#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
-
 struct poll_table_page {
 	struct poll_table_page * next;
 	struct poll_table_entry * entry;

diff --git a/include/linux/poll.h b/include/linux/poll.h
@@ -21,6 +21,8 @@
 #define WQUEUES_STACK_ALLOC	(MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
 #define N_INLINE_POLL_ENTRIES	(WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
 
+#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
+
 struct poll_table_struct;
 
 /*