minix/servers/vfs/threads.h

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#ifndef __VFS_WORKERS_H__
#define __VFS_WORKERS_H__
#include <minix/mthread.h>
#define thread_t mthread_thread_t
#define mutex_t mthread_mutex_t
#define cond_t mthread_cond_t
#define attr_t mthread_attr_t
#define threads_init mthread_init
#define yield mthread_yield
#define yield_all mthread_yield_all
#define mutex_init mthread_mutex_init
#define mutex_destroy mthread_mutex_destroy
#define mutex_lock mthread_mutex_lock
#define mutex_trylock mthread_mutex_trylock
#define mutex_unlock mthread_mutex_unlock
#define cond_init mthread_cond_init
#define cond_destroy mthread_cond_destroy
#define cond_wait mthread_cond_wait
#define cond_signal mthread_cond_signal
VFS: worker thread model overhaul The main purpose of this patch is to fix handling of unpause calls from PM while another call is ongoing. The solution to this problem sparked a full revision of the threading model, consisting of a large number of related changes: - all active worker threads are now always associated with a process, and every process has at most one active thread working for it; - the process lock is always held by a process's worker thread; - a process can now have both normal work and postponed PM work associated to it; - timer expiry and non-postponed PM work is done from the main thread; - filp garbage collection is done from a thread associated with VFS; - reboot calls from PM are now done from a thread associated with PM; - the DS events handler is protected from starting multiple threads; - support for a system worker thread has been removed; - the deadlock recovery thread has been replaced by a parameter to the worker_start() function; the number of worker threads has consequently been increased by one; - saving and restoring of global but per-thread variables is now centralized in worker_suspend() and worker_resume(); err_code is now saved and restored in all cases; - the concept of jobs has been removed, and job_m_in now points to a message stored in the worker thread structure instead; - the PM lock has been removed; - the separate exec lock has been replaced by a lock on the VM process, which was already being locked for exec calls anyway; - PM_UNPAUSE is now processed as a postponed PM request, from a thread associated with the target process; - the FP_DROP_WORK flag has been removed, since it is no longer more than just an optimization and only applied to processes operating on a pipe when getting killed; - assignment to "fp" now takes place only when obtaining new work in the main thread or a worker thread, when resuming execution of a thread, and in the special case of exiting processes during reboot; - there are no longer special cases where the yield() call is used to force a thread to run. Change-Id: I7a97b9b95c2450454a9b5318dfa0e6150d4e6858
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struct fproc;
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struct worker_thread {
thread_t w_tid;
mutex_t w_event_mutex;
cond_t w_event;
struct fproc *w_fp;
message w_m_in;
message w_m_out;
VFS: worker thread model overhaul The main purpose of this patch is to fix handling of unpause calls from PM while another call is ongoing. The solution to this problem sparked a full revision of the threading model, consisting of a large number of related changes: - all active worker threads are now always associated with a process, and every process has at most one active thread working for it; - the process lock is always held by a process's worker thread; - a process can now have both normal work and postponed PM work associated to it; - timer expiry and non-postponed PM work is done from the main thread; - filp garbage collection is done from a thread associated with VFS; - reboot calls from PM are now done from a thread associated with PM; - the DS events handler is protected from starting multiple threads; - support for a system worker thread has been removed; - the deadlock recovery thread has been replaced by a parameter to the worker_start() function; the number of worker threads has consequently been increased by one; - saving and restoring of global but per-thread variables is now centralized in worker_suspend() and worker_resume(); err_code is now saved and restored in all cases; - the concept of jobs has been removed, and job_m_in now points to a message stored in the worker thread structure instead; - the PM lock has been removed; - the separate exec lock has been replaced by a lock on the VM process, which was already being locked for exec calls anyway; - PM_UNPAUSE is now processed as a postponed PM request, from a thread associated with the target process; - the FP_DROP_WORK flag has been removed, since it is no longer more than just an optimization and only applied to processes operating on a pipe when getting killed; - assignment to "fp" now takes place only when obtaining new work in the main thread or a worker thread, when resuming execution of a thread, and in the special case of exiting processes during reboot; - there are no longer special cases where the yield() call is used to force a thread to run. Change-Id: I7a97b9b95c2450454a9b5318dfa0e6150d4e6858
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int w_err_code;
VFS: make all IPC asynchronous By decoupling synchronous drivers from VFS, we are a big step closer to supporting driver crashes under all circumstances. That is, VFS can't become stuck on IPC with a synchronous driver (e.g., INET) and can recover from crashing block drivers during open/close/ioctl or during communication with an FS. In order to maintain serialized communication with a synchronous driver, the communication is wrapped by a mutex on a per driver basis (not major numbers as there can be multiple majors with identical endpoints). Majors that share a driver endpoint point to a single mutex object. In order to support crashes from block drivers, the file reopen tactic had to be changed; first reopen files associated with the crashed driver, then send the new driver endpoint to FSes. This solves a deadlock between the FS and the block driver; - VFS would send REQ_NEW_DRIVER to an FS, but he FS only receives it after retrying the current request to the newly started driver. - The block driver would refuse the retried request until all files had been reopened. - VFS would reopen files only after getting a reply from the initial REQ_NEW_DRIVER. When a character special driver crashes, all associated files have to be marked invalid and closed (or reopened if flagged as such). However, they can only be closed if a thread holds exclusive access to it. To obtain exclusive access, the worker thread (which handles the new driver endpoint event from DS) schedules a new job to garbage collect invalid files. This way, we can signal the worker thread that was talking to the crashed driver and will release exclusive access to a file associated with the crashed driver and prevent the garbage collecting worker thread from dead locking on that file. Also, when a character special driver crashes, RS will unmap the driver and remap it upon restart. During unmapping, associated files are marked invalid instead of waiting for an endpoint up event from DS, as that event might come later than new read/write/select requests and thus cause confusion in the freshly started driver. When locking a filp, the usage counters are no longer checked. The usage counter can legally go down to zero during filp invalidation while there are locks pending. DS events are handled by a separate worker thread instead of the main thread as reopening files could lead to another crash and a stuck thread. An additional worker thread is then necessary to unlock it. Finally, with everything asynchronous a race condition in do_select surfaced. A select entry was only marked in use after succesfully sending initial select requests to drivers and having to wait. When multiple select() calls were handled there was opportunity that these entries were overwritten. This had as effect that some select results were ignored (and select() remained blocking instead if returning) or do_select tried to access filps that were not present (because thrown away by secondary select()). This bug manifested itself with sendrecs, but was very hard to reproduce. However, it became awfully easy to trigger with asynsends only.
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message *w_fs_sendrec;
message *w_drv_sendrec;
endpoint_t w_task;
struct dmap *w_dmap;
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struct worker_thread *w_next;
};
#endif