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> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Richard Weinberger <richard@nod.at> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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c240837fa7
1 changed files with 7 additions and 5 deletions
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@ -75,10 +75,13 @@ void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
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static int jffs2_garbage_collect_thread(void *_c)
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{
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struct jffs2_sb_info *c = _c;
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sigset_t hupmask;
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siginitset(&hupmask, sigmask(SIGHUP));
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allow_signal(SIGKILL);
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allow_signal(SIGSTOP);
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allow_signal(SIGCONT);
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allow_signal(SIGHUP);
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c->gc_task = current;
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complete(&c->gc_thread_start);
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@ -87,7 +90,7 @@ static int jffs2_garbage_collect_thread(void *_c)
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set_freezable();
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for (;;) {
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allow_signal(SIGHUP);
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sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
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again:
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spin_lock(&c->erase_completion_lock);
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if (!jffs2_thread_should_wake(c)) {
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@ -95,10 +98,9 @@ static int jffs2_garbage_collect_thread(void *_c)
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spin_unlock(&c->erase_completion_lock);
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jffs2_dbg(1, "%s(): sleeping...\n", __func__);
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schedule();
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} else
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} else {
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spin_unlock(&c->erase_completion_lock);
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}
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/* Problem - immediately after bootup, the GCD spends a lot
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* of time in places like jffs2_kill_fragtree(); so much so
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* that userspace processes (like gdm and X) are starved
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@ -150,7 +152,7 @@ static int jffs2_garbage_collect_thread(void *_c)
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}
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}
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/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
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disallow_signal(SIGHUP);
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sigprocmask(SIG_BLOCK, &hupmask, NULL);
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jffs2_dbg(1, "%s(): pass\n", __func__);
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if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
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