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vfs: no 'handle_io_response()' in regular VFS functions

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Calling 'handle_io_response()' in a regular VFS function (in contrast to a
post-signal hook) can cause problems if the caller of the VFS function holds
a lock which prevents the io response handler from returning.

With this commit, the user of the VFS becomes responsible for unblocking
threads which might be blocking after a failed 'queue_read()', 'queue_sync()'
or 'write()' call.

Fixes #2896
This commit is contained in:
Christian Prochaska 2018-07-04 14:09:01 +02:00 committed by Christian Helmuth
parent b4dd9bc802
commit e3005266b6
6 changed files with 73 additions and 19 deletions
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19
repos/libports/src/lib/libc/vfs_plugin.cc
View File

@ -422,6 +422,10 @@ ssize_t Libc::Vfs_plugin::write(Libc::File_descriptor *fd, const void *buf,
try {
out_result = VFS_THREAD_SAFE(handle->fs().write(handle, (char const *)buf, count, out_count));
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
} catch (Vfs::File_io_service::Insufficient_buffer) { }
} else {
@ -462,6 +466,9 @@ ssize_t Libc::Vfs_plugin::write(Libc::File_descriptor *fd, const void *buf,
} while (check.retry);
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
switch (out_result) {
case Result::WRITE_ERR_AGAIN: return Errno(EAGAIN);
case Result::WRITE_ERR_WOULD_BLOCK: return Errno(EWOULDBLOCK);
@ -552,6 +559,9 @@ ssize_t Libc::Vfs_plugin::read(Libc::File_descriptor *fd, void *buf,
} while (check.retry);
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
switch (out_result) {
case Result::READ_ERR_AGAIN: return Errno(EAGAIN);
case Result::READ_ERR_WOULD_BLOCK: return Errno(EWOULDBLOCK);
@ -645,6 +655,9 @@ ssize_t Libc::Vfs_plugin::getdirentries(Libc::File_descriptor *fd, char *buf,
} while (check.retry);
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
if ((out_result != Result::READ_OK) ||
(out_count < sizeof(Dirent))) {
return 0;
@ -979,6 +992,9 @@ int Libc::Vfs_plugin::symlink(const char *oldpath, const char *newpath)
Libc::suspend(check);
} while (check.retry);
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
_vfs_sync(handle);
VFS_THREAD_SAFE(handle->close());
@ -1078,6 +1094,9 @@ ssize_t Libc::Vfs_plugin::readlink(const char *path, char *buf, ::size_t buf_siz
} while (check.retry);
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
Libc::resume_all();
switch (out_result) {
case Result::READ_ERR_AGAIN: return Errno(EAGAIN);
case Result::READ_ERR_WOULD_BLOCK: return Errno(EWOULDBLOCK);

11
repos/os/include/vfs/file_io_service.h
View File

@ -47,8 +47,9 @@ struct Vfs::File_io_service : Interface
***********/
/*
* Exception, thrown when 'alloc_packet()' or 'submit_packet()' failed in the
* VFS plugin and the caller should wait for an IO response and try again.
* Exception, thrown when, for example, 'alloc_packet()' or
* 'submit_packet()' failed in the VFS plugin. The caller can try again
* after a previous VFS request is completed.
*/
struct Insufficient_buffer { };
@ -74,6 +75,9 @@ struct Vfs::File_io_service : Interface
* Queue read operation
*
* \return false if queue is full
*
* If the queue is full, the caller can try again after a previous VFS
* request is completed.
*/
virtual bool queue_read(Vfs_handle *, file_size)
{
@ -177,6 +181,9 @@ struct Vfs::File_io_service : Interface
* Queue sync operation
*
* \return false if queue is full
*
* If the queue is full, the caller can try again after a previous VFS
* request is completed.
*/
virtual bool queue_sync(Vfs_handle *) { return true; }

12
repos/os/src/lib/vfs/fs_file_system.h
View File

@ -140,12 +140,6 @@ class Vfs::Fs_file_system : public File_system
source.release_packet(packet);
/*
* Notify anyone who might have failed on
* 'alloc_packet()' or 'submit_packet()'
*/
_io_handler.handle_io_response(nullptr);
return READ_OK;
}
@ -222,12 +216,6 @@ class Vfs::Fs_file_system : public File_system
source.release_packet(packet);
/*
* Notify anyone who might have failed on
* 'alloc_packet()' or 'submit_packet()'
*/
_io_handler.handle_io_response(nullptr);
return SYNC_OK;
}
};

5
repos/ports/src/noux/rom_session_component.h
View File

@ -106,6 +106,11 @@ struct Noux::Vfs_dataspace
read_context.vfs_io_waiter.wait_for_io();
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
if (read_result != Vfs::File_io_service::READ_OK) {
Genode::error("Error reading dataspace from VFS");
rm.detach(addr);

25
repos/ports/src/noux/syscall.cc
View File

@ -103,11 +103,6 @@ bool Noux::Child::syscall(Noux::Session::Syscall sc)
size_t path_len = strlen(_sysio.stat_in.path);
uint32_t path_hash = hash_path(_sysio.stat_in.path, path_len);
/* XXX: remove sync */
Registered_no_delete<Vfs_io_waiter>
vfs_io_waiter(_vfs_io_waiter_registry);
Vfs::Directory_service::Stat stat_out;
_sysio.error.stat = _root_dir.stat(_sysio.stat_in.path, stat_out);
@ -668,6 +663,11 @@ bool Noux::Child::syscall(Noux::Session::Syscall sc)
read_context.vfs_io_waiter.wait_for_io();
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
symlink_handle->ds().close(symlink_handle);
_sysio.readlink_out.count = out_count;
@ -766,6 +766,11 @@ bool Noux::Child::syscall(Noux::Session::Syscall sc)
}
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
if (out_count != count) {
_sysio.error.symlink = Sysio::SYMLINK_ERR_NAME_TOO_LONG;
result = false;
@ -782,6 +787,11 @@ bool Noux::Child::syscall(Noux::Session::Syscall sc)
Vfs::File_io_service::SYNC_QUEUED)
sync_context.vfs_io_waiter.wait_for_io();
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
symlink_handle->ds().close(symlink_handle);
break;
@ -916,6 +926,11 @@ bool Noux::Child::syscall(Noux::Session::Syscall sc)
Vfs::File_io_service::SYNC_QUEUED)
sync_context.vfs_io_waiter.wait_for_io();
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
sync_handle->ds().close(sync_handle);
break;

20
repos/ports/src/noux/vfs_io_channel.h
View File

@ -79,6 +79,11 @@ struct Noux::Vfs_io_channel : Io_channel
while (_fh->fs().complete_sync(_fh) == Vfs::File_io_service::SYNC_QUEUED)
vfs_io_waiter.wait_for_io();
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
}
Vfs_io_channel(char const *path, char const *leaf_path,
@ -123,6 +128,11 @@ struct Noux::Vfs_io_channel : Io_channel
}
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
if (sysio.error.write != Vfs::File_io_service::WRITE_OK)
return false;
@ -160,6 +170,11 @@ struct Noux::Vfs_io_channel : Io_channel
vfs_io_waiter.wait_for_io();
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
if (sysio.error.read != Vfs::File_io_service::READ_OK)
return false;
@ -271,6 +286,11 @@ struct Noux::Vfs_io_channel : Io_channel
vfs_io_waiter.wait_for_io();
}
/* wake up threads blocking for 'queue_*()' or 'write()' */
_vfs_io_waiter_registry.for_each([] (Vfs_io_waiter &r) {
r.wakeup();
});
if ((read_result != Vfs::File_io_service::READ_OK) ||
(out_count != sizeof(dirent))) {
dirent = Vfs::Directory_service::Dirent();