lkml.org 
[lkml]   [2015]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subject->poll() instances shouldn't be indefinitely blocking
Take a look at this:
static unsigned int gsc_m2m_poll(struct file *file,
struct poll_table_struct *wait)
{
struct gsc_ctx *ctx = fh_to_ctx(file->private_data);
struct gsc_dev *gsc = ctx->gsc_dev;
int ret;

if (mutex_lock_interruptible(&gsc->lock))
return -ERESTARTSYS;

ret = v4l2_m2m_poll(file, ctx->m2m_ctx, wait);
mutex_unlock(&gsc->lock);

return ret;
}

a) ->poll() should not return -E...; callers expect just a bitmap of
POLL... values.

b) sure, it's nice that if this thing hangs, we'll be able to kill it.
However, if one's ->poll() can hang indefinitely, it means bad things
for poll(2), select(2), etc. semantics. What the hell had been intended
there?

c) a bunch of v4l2_m2m_poll() callers are also taking some kind of
mutex; AFAICS, all of those appear bogus (the rest of them do not
play wiht ERESTARTSYS, just plain mutex_lock() for those).

What's going on there?


\
 
 \ /
  Last update: 2015-11-27 06:21    [W:0.069 / U:0.292 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site