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5f820f648c
f_op->poll is the only vfs operation which is not allowed to sleep. It's because poll and select implementation used task state to synchronize against wake ups, which doesn't have to be the case anymore as wait/wake interface can now use custom wake up functions. The non-sleep restriction can be a bit tricky because ->poll is not called from an atomic context and the result of accidentally sleeping in ->poll only shows up as temporary busy looping when the timing is right or rather wrong. This patch converts poll/select to use custom wake up function and use separate triggered variable to synchronize against wake up events. The only added overhead is an extra function call during wake up and negligible. This patch removes the one non-sleep exception from vfs locking rules and is beneficial to userland filesystem implementations like FUSE, 9p or peculiar fs like spufs as it's very difficult for those to implement non-sleeping poll method. While at it, make the following cosmetic changes to make poll.h and select.c checkpatch friendly. * s/type * symbol/type *symbol/ : three places in poll.h * remove blank line before EXPORT_SYMBOL() : two places in select.c Oleg: spotted missing barrier in poll_schedule_timeout() Davide: spotted missing write barrier in pollwake() Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Eric Van Hensbergen <ericvh@gmail.com> Cc: Ron Minnich <rminnich@sandia.gov> Cc: Ingo Molnar <mingo@elte.hu> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Brad Boyer <flar@allandria.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Roland McGrath <roland@redhat.com> Cc: Mauro Carvalho Chehab <mchehab@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
137 lines
3.5 KiB
C
137 lines
3.5 KiB
C
#ifndef _LINUX_POLL_H
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#define _LINUX_POLL_H
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#include <asm/poll.h>
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#ifdef __KERNEL__
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#include <linux/compiler.h>
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#include <linux/wait.h>
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#include <linux/string.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <asm/uaccess.h>
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/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
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additional memory. */
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#define MAX_STACK_ALLOC 832
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#define FRONTEND_STACK_ALLOC 256
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#define SELECT_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define POLL_STACK_ALLOC FRONTEND_STACK_ALLOC
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#define WQUEUES_STACK_ALLOC (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
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#define N_INLINE_POLL_ENTRIES (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
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#define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
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struct poll_table_struct;
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/*
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* structures and helpers for f_op->poll implementations
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*/
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typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
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typedef struct poll_table_struct {
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poll_queue_proc qproc;
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} poll_table;
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static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
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{
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if (p && wait_address)
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p->qproc(filp, wait_address, p);
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}
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static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
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{
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pt->qproc = qproc;
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}
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struct poll_table_entry {
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struct file *filp;
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wait_queue_t wait;
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wait_queue_head_t *wait_address;
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};
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/*
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* Structures and helpers for sys_poll/sys_poll
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*/
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struct poll_wqueues {
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poll_table pt;
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struct poll_table_page *table;
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struct task_struct *polling_task;
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int triggered;
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int error;
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int inline_index;
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struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
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};
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extern void poll_initwait(struct poll_wqueues *pwq);
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extern void poll_freewait(struct poll_wqueues *pwq);
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extern int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
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ktime_t *expires, unsigned long slack);
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static inline int poll_schedule(struct poll_wqueues *pwq, int state)
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{
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return poll_schedule_timeout(pwq, state, NULL, 0);
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}
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/*
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* Scaleable version of the fd_set.
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*/
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typedef struct {
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unsigned long *in, *out, *ex;
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unsigned long *res_in, *res_out, *res_ex;
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} fd_set_bits;
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/*
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* How many longwords for "nr" bits?
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*/
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#define FDS_BITPERLONG (8*sizeof(long))
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#define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
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#define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long))
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/*
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* We do a VERIFY_WRITE here even though we are only reading this time:
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* we'll write to it eventually..
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*
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* Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
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*/
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static inline
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int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
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{
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nr = FDS_BYTES(nr);
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if (ufdset)
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return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
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memset(fdset, 0, nr);
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return 0;
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}
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static inline unsigned long __must_check
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set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
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{
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if (ufdset)
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return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
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return 0;
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}
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static inline
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void zero_fd_set(unsigned long nr, unsigned long *fdset)
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{
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memset(fdset, 0, FDS_BYTES(nr));
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}
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#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)
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extern int do_select(int n, fd_set_bits *fds, struct timespec *end_time);
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extern int do_sys_poll(struct pollfd __user * ufds, unsigned int nfds,
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struct timespec *end_time);
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extern int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
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fd_set __user *exp, struct timespec *end_time);
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extern int poll_select_set_timeout(struct timespec *to, long sec, long nsec);
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#endif /* KERNEL */
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#endif /* _LINUX_POLL_H */
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