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VFS: fix pipe resumption delay bug

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Commit 723e513 erroneously removed a yield() call from VFS which was
necessary to get resumed pipe read/write threads to run before VFS
blocks on receive().  The removal caused those threads to run only
once VFS received another message, effectively slowing down activity
on pipes to a crawl in some cases.

Instead of readding the yield() call, this patch restructures the
get_work() code to go back through the main message loop even when no
new work is received, thus ensuring that newly started threads are
always activated without requiring a special case.

This fixes #65.

Change-Id: I59b7fb9e403d87dba1a5deecb04539cc37517742
This commit is contained in:
David van Moolenbroek 2015-06-19 22:06:19 +00:00
parent e1e2bc96d2
commit 5055c7ea51
1 changed files with 19 additions and 23 deletions
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42
minix/servers/vfs/main.c
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@ -41,7 +41,7 @@ static void do_init_root(void);
static void handle_work(void (*func)(void)); static void handle_work(void (*func)(void));
static void reply(message *m_out, endpoint_t whom, int result); static void reply(message *m_out, endpoint_t whom, int result);
static void get_work(void); static int get_work(void);
static void service_pm(void); static void service_pm(void);
static int unblock(struct fproc *rfp); static int unblock(struct fproc *rfp);
@ -74,7 +74,12 @@ int main(void)
yield_all(); /* let other threads run */ yield_all(); /* let other threads run */
self = NULL; self = NULL;
send_work(); send_work();
get_work();
/* The get_work() function returns TRUE if we have a new message to
* process. It returns FALSE if it spawned other thread activities.
*/
if (!get_work())
continue;
transid = TRNS_GET_ID(m_in.m_type); transid = TRNS_GET_ID(m_in.m_type);
if (IS_VFS_FS_TRANSID(transid)) { if (IS_VFS_FS_TRANSID(transid)) {
@ -476,28 +481,23 @@ void thread_cleanup(void)
/*===========================================================================* /*===========================================================================*
* get_work * * get_work *
*===========================================================================*/ *===========================================================================*/
static void get_work() static int get_work(void)
{ {
/* Normally wait for new input. However, if 'reviving' is /* Normally wait for new input. However, if 'reviving' is nonzero, a
* nonzero, a suspended process must be awakened. * suspended process must be awakened. Return TRUE if there is a message to
* process (usually newly received, but possibly a resumed request), or FALSE
* if a thread for other activities has been spawned instead.
*/ */
int r, found_one, proc_p; int r, proc_p;
register struct fproc *rp; register struct fproc *rp;
while (reviving != 0) { if (reviving != 0) {
found_one = FALSE;
/* Find a suspended process. */ /* Find a suspended process. */
for (rp = &fproc[0]; rp < &fproc[NR_PROCS]; rp++) for (rp = &fproc[0]; rp < &fproc[NR_PROCS]; rp++)
if (rp->fp_pid != PID_FREE && (rp->fp_flags & FP_REVIVED)) { if (rp->fp_pid != PID_FREE && (rp->fp_flags & FP_REVIVED))
found_one = TRUE; /* Found a suspended process */ return unblock(rp); /* So main loop can process job */
if (unblock(rp))
return; /* So main loop can process job */
send_work();
}
if (!found_one) /* Consistency error */ panic("VFS: get_work couldn't revive anyone");
panic("VFS: get_work couldn't revive anyone");
} }
for(;;) { for(;;) {
@ -510,11 +510,6 @@ static void get_work()
if (proc_p < 0 || proc_p >= NR_PROCS) fp = NULL; if (proc_p < 0 || proc_p >= NR_PROCS) fp = NULL;
else fp = &fproc[proc_p]; else fp = &fproc[proc_p];
if (m_in.m_type == EDEADSRCDST) {
printf("VFS: failed ipc_sendrec\n");
return; /* Failed 'ipc_sendrec' */
}
/* Negative who_p is never used to access the fproc array. Negative /* Negative who_p is never used to access the fproc array. Negative
* numbers (kernel tasks) are treated in a special way. * numbers (kernel tasks) are treated in a special way.
*/ */
@ -536,8 +531,9 @@ static void get_work()
fproc[who_p].fp_endpoint, who_e); fproc[who_p].fp_endpoint, who_e);
} }
return; return TRUE;
} }
/* NOTREACHED */
} }
/*===========================================================================* /*===========================================================================*