Subject: + signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch added to -mm tree
To: oleg@xxxxxxxxxx,dwmw2@xxxxxxxxxxxxx,fweisbec@xxxxxxxxx,geert@xxxxxxxxxxxxxx,mathieu.desnoyers@xxxxxxxxxxxx,mingo@xxxxxxxxxx,peterz@xxxxxxxxxxxxx,richard@xxxxxx,rostedt@xxxxxxxxxxx,tj@xxxxxxxxxx,viro@xxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 15 Apr 2014 12:28:52 -0700
The patch titled
Subject: signals: jffs2: fix the wrong usage of disallow_signal()
has been added to the -mm tree. Its filename is
signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Richard Weinberger <richard@xxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/jffs2/background.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff -puN fs/jffs2/background.c~signals-jffs2-fix-the-wrong-usage-of-disallow_signal fs/jffs2/background.c
--- a/fs/jffs2/background.c~signals-jffs2-fix-the-wrong-usage-of-disallow_signal
+++ a/fs/jffs2/background.c
@@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(s
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(
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(
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(
}
}
/* 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) {
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
signals-kill-sigfindinword.patch
signals-s-siginitset-sigemptyset-in-do_sigtimedwait.patch
signals-kill-rm_from_queue-change-prepare_signal-to-use-for_each_thread.patch
signals-rename-rm_from_queue_full-to-flush_sigqueue_mask.patch
signals-cleanup-the-usage-of-t-current-in-do_sigaction.patch
signals-mv-disallow_signal-from-schedh-exitc-to-signal.patch
signals-jffs2-fix-the-wrong-usage-of-disallow_signal.patch
signals-kill-the-obsolete-sigdelset-and-recalc_sigpending-in-allow_signal.patch
signals-disallow_signal-should-flush-the-potentially-pending-signal.patch
signals-introduce-kernel_sigaction.patch
signals-change-wait_for_helper-to-use-kernel_sigaction.patch
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