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Make the UP/DOWN threads hold on to their own private mutex while doing

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work.

This prevents people from sleeping in the UP/DOWN I/O path by mistake
or design (doing so almost invariably result in deadlocks since it
stalls all I/O processing in the given direction.

Sponsored by:   DARPA & NAI Labs.
This commit is contained in:
Poul-Henning Kamp 2002-09-27 21:24:40 +00:00
parent 8ac8480b86
commit b1937dd1ca
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=104063
1 changed files with 26 additions and 2 deletions
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28
sys/geom/geom_kern.c
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@ -59,16 +59,37 @@ static struct proc *g_up_proc;
int g_debugflags;
/*
* G_UP and G_DOWN are the two threads which push I/O through the
* stack.
*
* Things are procesed in a FIFO order, but these threads could be
* part of I/O prioritization by deciding which bios/bioqs to service
* in what order.
*
* We have only one thread in each direction, it is belived that until
* a very non-trivial workload in the UP/DOWN path this will be enough,
* but more than one can actually be run without problems.
*
* Holding the "mymutex" is a debugging feature: It prevents people
* from sleeping in the UP/DOWN I/O path by mistake or design (doing
* so almost invariably result in deadlocks since it stalls all I/O
* processing in the given direction.
*/
static void
g_up_procbody(void)
{
struct proc *p = g_up_proc;
struct thread *tp = FIRST_THREAD_IN_PROC(p);
struct mtx mymutex;
mtx_init(&mymutex, "g_up", MTX_DEF, 0);
mtx_lock(&mymutex);
curthread->td_base_pri = PRIBIO;
for(;;) {
g_io_schedule_up(tp);
tsleep(&g_wait_up, PRIBIO, "g_up", hz/10);
msleep(&g_wait_up, &mymutex, PRIBIO, "g_up", hz/10);
}
}
@ -85,11 +106,14 @@ g_down_procbody(void)
{
struct proc *p = g_down_proc;
struct thread *tp = FIRST_THREAD_IN_PROC(p);
struct mtx mymutex;
mtx_init(&mymutex, "g_down", MTX_DEF, 0);
mtx_lock(&mymutex);
curthread->td_base_pri = PRIBIO;
for(;;) {
g_io_schedule_down(tp);
tsleep(&g_wait_down, PRIBIO, "g_down", hz/10);
msleep(&g_wait_down, &mymutex, PRIBIO, "g_down", hz/10);
}
}