From: mita@miraclelinux.com (Akinobu Mita)
To: Keith Owens <kaos@sgi.com>
Cc: linux-kernel@vger.kernel.org, Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Russell King <rmk@arm.linux.org.uk>, Ian Molton <spyro@f2s.com>,
dev-etrax@axis.com, David Howells <dhowells@redhat.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Linus Torvalds <torvalds@osdl.org>,
linux-ia64@vger.kernel.org,
Hirokazu Takata <takata@linux-m32r.org>,
linux-m68k@vger.kernel.org, Greg Ungerer <gerg@uclinux.org>,
linux-mips@linux-mips.org, parisc-linux@parisc-linux.org,
linuxppc-dev@ozlabs.org, linux390@de.ibm.com,
linuxsh-dev@lists.sourceforge.net,
linuxsh-shmedia-dev@lists.sourceforge.net,
sparclinux@vger.kernel.org, ultralinux@vger.kernel.org,
Miles Bader <uclinux-v850@lsi.nec.co.jp>, Andi Kleen <ak@suse.de>,
Chris Zankel <chris@zankel.net>
Subject: Re: [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h
Date: Thu, 26 Jan 2006 11:13:18 +0900 [thread overview]
Message-ID: <20060126021318.GB6648@miraclelinux.com> (raw)
In-Reply-To: <24086.1138190083@ocs3.ocs.com.au>
On Wed, Jan 25, 2006 at 10:54:43PM +1100, Keith Owens wrote:
> Be very, very careful about using these generic *_bit() routines if the
> architecture supports non-maskable interrupts.
>
> NMI events can occur at any time, including when interrupts have been
> disabled by *_irqsave(). So you can get NMI events occurring while a
> *_bit fucntion is holding a spin lock. If the NMI handler also wants
> to do bit manipulation (and they do) then you can get a deadlock
> between the original caller of *_bit() and the NMI handler.
>
> Doing any work that requires spinlocks in an NMI handler is just asking
> for deadlock problems. The generic *_bit() routines add a hidden
> spinlock behind what was previously a safe operation. I would even say
> that any arch that supports any type of NMI event _must_ define its own
> bit routines that do not rely on your _atomic_spin_lock_irqsave() and
> its hash of spinlocks.
At least cris and parisc are using similar *_bit function on SMP.
I will add your advise in comment.
--- ./include/asm-generic/bitops.h.orig 2006-01-26 10:56:00.000000000 +0900
+++ ./include/asm-generic/bitops.h 2006-01-26 11:01:28.000000000 +0900
@@ -50,6 +50,16 @@ extern raw_spinlock_t __atomic_hash[ATOM
* C language equivalents written by Theodore Ts'o, 9/26/92
*/
+/*
+ * NMI events can occur at any time, including when interrupts have been
+ * disabled by *_irqsave(). So you can get NMI events occurring while a
+ * *_bit fucntion is holding a spin lock. If the NMI handler also wants
+ * to do bit manipulation (and they do) then you can get a deadlock
+ * between the original caller of *_bit() and the NMI handler.
+ *
+ * by Keith Owens
+ */
+
static __inline__ void set_bit(int nr, volatile unsigned long *addr)
{
unsigned long mask = BITOP_MASK(nr);
next prev parent reply other threads:[~2006-01-26 2:13 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-25 11:26 [PATCH 0/6] RFC: use include/asm-generic/bitops.h Akinobu Mita
2006-01-25 11:28 ` [PATCH 1/6] {set,clear,test}_bit() related cleanup Akinobu Mita
2006-01-25 11:46 ` Andi Kleen
2006-01-26 16:14 ` Pavel Machek
2006-01-26 16:47 ` Russell King
2006-01-26 19:14 ` Paul Jackson
2006-01-25 11:30 ` [PATCH 2/6] use non atomic operations for minix_*_bit() and ext2_*_bit() Akinobu Mita
2006-01-25 11:32 ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Akinobu Mita
2006-01-25 11:54 ` Keith Owens
2006-01-26 2:13 ` Akinobu Mita [this message]
2006-01-26 2:19 ` Akinobu Mita
2006-01-25 20:02 ` Russell King
2006-01-25 20:59 ` Grant Grundler
2006-01-26 3:27 ` Akinobu Mita
2006-01-26 3:29 ` [PATCH 1/12] generic *_bit() Akinobu Mita
2006-02-01 15:11 ` Chen, Kenneth W
2006-02-01 18:02 ` Christoph Hellwig
2006-02-01 18:07 ` Chen, Kenneth W
2006-02-01 19:19 ` Russell King
2006-02-01 19:25 ` Chen, Kenneth W
2006-02-01 19:35 ` Russell King
2006-02-03 10:24 ` Geert Uytterhoeven
2006-02-03 10:27 ` Russell King
2006-02-01 19:39 ` Grant Grundler
2006-02-01 21:41 ` Chen, Kenneth W
2006-02-01 22:09 ` Grant Grundler
2006-02-01 22:49 ` Anton Altaparmakov
2006-02-02 0:08 ` Grant Grundler
2006-02-02 8:52 ` Anton Altaparmakov
2006-02-02 10:13 ` Andreas Schwab
2006-02-02 22:43 ` Paul Mackerras
2006-01-26 3:30 ` [PATCH 2/12] generic __ffs() Akinobu Mita
2006-01-26 3:31 ` [PATCH 3/12] generic ffz() Akinobu Mita
2006-01-26 8:21 ` Michael Tokarev
2006-01-27 6:39 ` [PATCH] parisc: add ()-pair in __ffs() Akinobu Mita
2006-01-26 3:32 ` [PATCH 4/12] generic fls() and fls64() Akinobu Mita
2006-01-26 3:33 ` [PATCH 5/12] generic find_{next,first}{,_zero}_bit() Akinobu Mita
2006-01-26 3:34 ` [PATCH 6/12] generic sched_find_first_bit() Akinobu Mita
2006-01-26 3:35 ` [PATCH 7/12] generic ffs() Akinobu Mita
2006-01-26 3:36 ` [PATCH 8/12] generic hweight{32,16,8}() Akinobu Mita
2006-01-26 7:12 ` Balbir Singh
2006-01-26 10:04 ` Rutger Nijlunsing
2006-01-27 4:55 ` Akinobu Mita
2006-01-27 5:40 ` Balbir Singh
2006-01-27 6:40 ` Akinobu Mita
2006-01-31 11:14 ` Balbir Singh
2006-01-26 18:57 ` Bryan O'Sullivan
2006-01-27 4:43 ` Akinobu Mita
2006-01-27 5:23 ` Bryan O'Sullivan
2006-01-26 3:36 ` [PATCH 9/12] generic hweight64() Akinobu Mita
2006-01-26 7:05 ` Balbir Singh
2006-01-26 3:38 ` [PATCH 10/12] generic ext2_{set,clear,test,find_first_zero,find_next_zero}_bit() Akinobu Mita
2006-01-26 3:38 ` [PATCH 11/12] generic ext2_{set,clear}_bit_atomic() Akinobu Mita
2006-01-26 3:39 ` [PATCH 12/12] generic minix_{test,set,test_and_clear,test,find_first_zero}_bit() Akinobu Mita
2006-01-25 23:25 ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Ian Molton
2006-01-26 0:06 ` Richard Henderson
2006-01-26 4:34 ` Edgar Toernig
2006-01-26 17:30 ` Richard Henderson
2006-01-26 8:55 ` Russell King
2006-01-26 16:18 ` [parisc-linux] " Grant Grundler
2006-01-26 16:30 ` Nicolas Pitre
2006-01-26 16:40 ` Russell King
2006-01-26 23:04 ` Grant Grundler
2006-01-26 23:03 ` Russell King
2006-01-29 7:12 ` Stuart Brady
2006-01-30 4:03 ` David S. Miller
2006-01-30 17:06 ` Ralf Baechle
2006-01-30 19:50 ` Stuart Brady
2006-01-30 23:02 ` David S. Miller
2006-01-27 0:28 ` [parisc-linux] Re: [PATCH 3/6] C-language equivalents of John David Anglin
2006-01-27 12:51 ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Hirokazu Takata
2006-01-30 3:29 ` Akinobu Mita
2006-01-25 11:34 ` [PATCH 5/6] fix warning on test_ti_thread_flag() Akinobu Mita
2006-01-25 12:28 ` Geert Uytterhoeven
2006-01-25 22:28 ` Paul Mackerras
2006-01-26 0:04 ` David S. Miller
2006-01-25 11:35 ` [PATCH 6/6] remove unused generic bitops in include/linux/bitops.h Akinobu Mita
[not found] ` <20060125113336.GE18584@miraclelinux.com>
2006-01-26 1:49 ` [PATCH 4/6] use include/asm-generic/bitops for each architecture Akinobu Mita
2006-01-26 2:37 ` Grant Grundler
2006-01-27 13:04 ` Hirokazu Takata
2006-01-30 3:15 ` Akinobu Mita
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