lkml.org 
[lkml]   [2014]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH RESEND2 07/11] signals: jffs2: fix the wrong usage of disallow_signal()
jffs2_garbage_collect_thread() does disallow_signal(SIGHUP) around
jffs2_garbage_collect_pass() and the comment says "We don't want
SIGHUP to interrupt us".

But disallow_signal() can't ensure that jffs2_garbage_collect_pass()
won't be interrupted by SIGHUP, the problem is that SIGHUP can be
already pending when disallow_signal() is called, and in this case
any interruptible sleep won't block.

Note: this is in fact because disallow_signal() is buggy and should
be fixed, see the next changes.

But there is another reason why disallow_signal() is wrong: SIG_IGN
set by disallow_signal() silently discards any SIGHUP which can be
sent before the next allow_signal(SIGHUP).

Change this code to use sigprocmask(SIG_UNBLOCK/SIG_BLOCK, SIGHUP).
This even matches the old (and wrong) semantics allow/disallow had
when this logic was written.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
fs/jffs2/background.c | 12 +++++++-----
1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
index 2b60ce1..bb9cebc 100644
--- a/fs/jffs2/background.c
+++ b/fs/jffs2/background.c
@@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
static int jffs2_garbage_collect_thread(void *_c)
{
struct jffs2_sb_info *c = _c;
+ sigset_t hupmask;

+ siginitset(&hupmask, sigmask(SIGHUP));
allow_signal(SIGKILL);
allow_signal(SIGSTOP);
allow_signal(SIGCONT);
+ allow_signal(SIGHUP);

c->gc_task = current;
complete(&c->gc_thread_start);
@@ -87,7 +90,7 @@ static int jffs2_garbage_collect_thread(void *_c)

set_freezable();
for (;;) {
- allow_signal(SIGHUP);
+ sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
again:
spin_lock(&c->erase_completion_lock);
if (!jffs2_thread_should_wake(c)) {
@@ -95,10 +98,9 @@ static int jffs2_garbage_collect_thread(void *_c)
spin_unlock(&c->erase_completion_lock);
jffs2_dbg(1, "%s(): sleeping...\n", __func__);
schedule();
- } else
+ } else {
spin_unlock(&c->erase_completion_lock);
-
-
+ }
/* Problem - immediately after bootup, the GCD spends a lot
* of time in places like jffs2_kill_fragtree(); so much so
* that userspace processes (like gdm and X) are starved
@@ -150,7 +152,7 @@ static int jffs2_garbage_collect_thread(void *_c)
}
}
/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
- disallow_signal(SIGHUP);
+ sigprocmask(SIG_BLOCK, &hupmask, NULL);

jffs2_dbg(1, "%s(): pass\n", __func__);
if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
--
1.5.5.1


\
 
 \ /
  Last update: 2014-04-15 21:01    [W:0.090 / U:11.956 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site