f707937192
Previously, processing of some replies coming from character drivers could block on locks, and therefore, such processing was done from threads that were associated to the character driver process. The hidden consequence of this was that if all threads were in use, VFS could drop replies coming from the driver. This patch returns VFS to a situation where the replies from character drivers are processed instantly from the main thread, by removing the situations that may cause VFS to block while handling those replies. - change the locking model for select, so that it will never block on any processing that happens after the select call has been set up, in particular processing of character driver select replies; - clearly mark all select routines that may never block; - protect against race conditions in do_select as result of the locking that still does happen there (as is required for pipes); - also handle select timers from the main thread; - move processing of character driver replies into device.c. Change-Id: I4dc8e69f265cbd178de0fbf321d35f58f067cc57
51 lines
1.9 KiB
C
51 lines
1.9 KiB
C
#ifndef __VFS_FILE_H__
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#define __VFS_FILE_H__
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/* This is the filp table. It is an intermediary between file descriptors and
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* inodes. A slot is free if filp_count == 0.
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*/
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EXTERN struct filp {
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mode_t filp_mode; /* RW bits, telling how file is opened */
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int filp_flags; /* flags from open and fcntl */
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int filp_state; /* state for crash recovery */
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int filp_count; /* how many file descriptors share this slot?*/
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struct vnode *filp_vno; /* vnode belonging to this file */
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off_t filp_pos; /* file position */
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mutex_t filp_lock; /* lock to gain exclusive access */
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struct fproc *filp_softlock; /* if not NULL; this filp didn't lock the
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* vnode. Another filp already holds a lock
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* for this thread */
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/* the following fields are for select() and are owned by the generic
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* select() code (i.e., fd-type-specific select() code can't touch these).
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* These fields may be changed without holding the filp lock.
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*/
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int filp_selectors; /* select()ing processes blocking on this fd */
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int filp_select_ops; /* interested in these SEL_* operations */
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int filp_select_flags; /* Select flags for the filp */
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/* following are for fd-type-specific select() */
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int filp_pipe_select_ops;
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} filp[NR_FILPS];
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#define FILP_CLOSED 0 /* filp_mode: associated device closed */
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#define FS_NORMAL 000 /* file descriptor can be used normally */
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#define FS_NEEDS_REOPEN 001 /* file descriptor needs to be re-opened */
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#define FS_INVALIDATED 002 /* file was invalidated */
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#define FSF_UPDATE 001 /* The driver should be informed about new
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* state.
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*/
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#define FSF_BUSY 002 /* Select operation sent to driver but no
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* reply yet.
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*/
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#define FSF_RD_BLOCK 010 /* Read request is blocking, the driver should
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* keep state.
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*/
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#define FSF_WR_BLOCK 020 /* Write request is blocking */
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#define FSF_ERR_BLOCK 040 /* Exception request is blocking */
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#define FSF_BLOCKED 070
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#endif
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