- 11 Nov, 2004 38 commits
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Hidetoshi Seto authored
NPTL has 3 control counters (total/wake/woken). so NPTL can know: "how many threads enter to wait"(total), "how many threads receive wake signal"(wake), and "how many threads exit waiting"(woken). Abstraction of pthread_cond_wait and pthread_cond_signal are: A01 pthread_cond_wait { A02 timeout = 0; A03 lock(counters); A04 total++; A05 val = get_from(futex); A06 unlock(counters); A07 A08 sys_futex(futex, FUTEX_WAIT, val, timeout); A09 A10 lock(counters); A11 woken++; A12 unlock(counters); A13 } B01 pthread_cond_signal { B02 lock(counters); B03 if(total>wake) { /* if there is waiter */ B04 wake++; B05 update_val(futex); B06 sys_futex(futex, FUTEX_WAKE, 1); B07 } B08 unlock(counters); B09 } What we have to notice is: FUTEX_WAKE could be called before FUTEX_WAIT have called (at A07). In such case, FUTEX_WAKE will fail if there is no thread in waitqueue. However, since pthread_cond_signal do not only wake++ but also update_val(futex), next FUTEX_WAIT will fail with -EWOULDBLOCK because the val passed to WAIT is now not equal to updated val. Therefore, as the result, it seems that the WAKE wakes the WAIT. === The bug will appear if 2 pair of wait & wake called at (nearly)once: * Assume 4 threads, wait_A, wait_B, wake_X, and wake_Y * counters start from [total/wake/woken]=[0/0/0] * the val of futex starts from (0), update means inclement of the val. * there is no thread in waitqueue on the futex. [simulation] wait_A: calls pthread_cond_wait: total++, prepare to call FUTEX_WAIT with val=0. # status: [1/0/0] (0) queue={}(empty) # wake_X: calls pthread_cond_signal: no one in waitqueue, just wake++ and update futex val. # status: [1/1/0] (1) queue={}(empty) # wait_B: calls pthread_cond_wait: total++, prepare to call FUTEX_WAIT with val=1. # status: [2/1/0] (1) queue={}(empty) # wait_A: calls FUTEX_WAIT with val=0: after queueing, compare val. 0!=1 ... this should be blocked... # status: [2/1/0] (1) queue={A} # wait_B: calls FUTEX_WAIT with val=1: after queueing, compare val. 1==1 ... OK, let's schedule()... # status: [2/1/0] (1) queue={A,B} (B=sleeping) # wake_Y: calls pthread_cond_signal: A is in waitqueue ... dequeue A, wake++ and update futex val. # status: [2/2/0] (2) queue={B} (B=sleeping) # wait_A: end of FUTEX_WAIT with val=0: try to dequeue but already dequeued, return anyway. # status: [2/2/0] (2) queue={B} (B=sleeping) # wait_A: end of pthread_cond_wait: woken++. # status: [2/2/1] (2) queue={B} (B=sleeping) # This is bug: wait_A: wakeup wait_B: sleeping wake_X: wake A wake_Y: wake A again if subsequent wake_Z try to wake B: wake_Z: calls pthread_cond_signal: since total==wake, do nothing. # status: [2/2/1] (2) queue={B} (B=sleeping) # If wait_C comes, B become to can be woken, but C... This bug makes the waitqueue to trap some threads in it all time. ==== > - According to man of futex: > "If the futex was not equal to the expected value, the operation > returns -EWOULDBLOCK." > but now, here is no description about the rare case: > "returns 0 if the futex was not equal to the expected value, but > the process was woken by a FUTEX_WAKE call." > this behavior on rare case causes the hang which I found. So to avoid this problem, my patch shut up the window that you said: > The patch certainly looks sensible - I can see that without the patch, > there is a window in which this process is pointlessly queued up on the > futex and that in this window a wakeup attempt might do a bad thing. ===== In short: There is an un-documented behavior of futex_wait. This behavior misleads NPTL to wake a thread doubly, as the result, causes an application hang. Signed-off-by:Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Signed-off-by:
Andrew Morton <akpm@osdl.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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Paolo \'Blaisorblade\' Giarrusso authored
From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it> Cc: Ulrich Drepper <drepper@redhat.com> Using NPTL, getpid() sometimes delivers the wrong pid, since it uses the one buffered in TLS from previous calls. This buffered pid isn't discarded, when a child is created by a clone(). So, as a workaround, UML should use a direct kernel call to bypass the lib. Also, I (Paolo) went replacing all remaining calls of getpid() with os_getpid(), to make sure they use the syscall and not the normal glibc definition. Signed-off-by:Bodo Stroesser <bstroesser@fujitsu-siemens.com> Signed-off-by:
Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it> Signed-off-by:
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Mikael Starvik authored
Changed maintainer for CRIS architecture to Mikael Starvik. Signed-off-by:
Mikael Starvik <starvik@axis.com> Signed-off-by:
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Mikael Starvik authored
Update Makefiles under drivers/ to compile CRIS drivers. Signed-off-by:
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Mikael Starvik authored
Move drivers from arch/cris/arch-v10/drivers/ to drivers/. Signed-off-by:
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Mikael Starvik authored
Handled console setup arguments on kernel command line. Signed-off-by:
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Mikael Starvik authored
Added profiler. Optimized MMU refill handling. Improved multiple interrupt handling. Signed-off-by:
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Mikael Starvik authored
USB host driver for CRIS. Signed-off-by:
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Mikael Starvik authored
Updated IDE driver for Linux 2.6.9. Signed-off-by:
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Mikael Starvik authored
Use generic MII interface. Signed-off-by:
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Mikael Starvik authored
Updates for 2.6.9 in basic character based drivers. Signed-off-by:
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Mikael Starvik authored
Configuration and build updates for 2.6.9. Signed-off-by:
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Andrew Morton authored
arch/x86_64/ia32/ia32_aout.c: In function `load_aout_binary': arch/x86_64/ia32/ia32_aout.c:400: error: `IA32_STACK_TOP' undeclared (first use in this function) Cc: <ak@muc.de> Signed-off-by:
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Pawel Sikora authored
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David Howells authored
The attached patch makes the presence of /proc/kcore conditional on CONFIG_MMU being configured on. Signed-Off-By:
David Howells <dhowells@redhat.com> Signed-off-by:
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David Howells authored
The attached patch fixes an uninitialised variable warning in ext3. The compiler is wrong in this case because it can't analyse the code sufficiently. Signed-Off-By:
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David Howells authored
The attached patch fixes fork to get rid of the assumption that THREAD_SIZE >= PAGE_SIZE (on the FR-V the smallest available page size is 16KB). Signed-Off-By:
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Anton Blanchard authored
A few small fixes: - Check for the model property before using it. Also check for the correct property name for nighthawk. - Check for the existence of freeze-time-base before using it to synchronize timebases instead of making it conditional on !LPAR Signed-off-by:
Anton Blanchard <anton@samba.org> Signed-off-by:
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Anton Blanchard authored
It was possible to hotplug add a new cpu that was larger than numnode. This meant we had a cpu with a node id that didnt have any NODE_DATA() backing it. The following patch catches this in numa_setup_cpu and forces the node to 0. We also make a pass through all cpus at boot to look for the maximum node id - this catches the case at boot. As for hotplug, since the node doesnt have any memory backing it (otherwise the node would have been onlined) then we can assume the machine isnt configured for performance and just force the cpu into node 0. Signed-off-by:
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Anton Blanchard authored
When fully configured, some POWER5 boxes can have much more than 4 IDE interfaces. Increase the limit to reflect this. Signed-off-by:
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Stephen Rothwell authored
This last patch is a bit if a mess because it mainly consists of combining some single use small functions into their callers and rearranging some other code. Some intermediate variables are introduced and some code is restructured to improve its readablility (and hopefully maintainability). Overall there are no semantic changes. Signed-off-by:
Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by:
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Stephen Rothwell authored
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Stephen Rothwell authored
This patch starts the improvement of the style of the MF code: - remove a union that is used where casts suffice - add a helper function (signal_ce_msg_simple) and use it - replace some painful code that converts a byte array to a couple of u32's and then shifts and masks the bytes back out. Signed-off-by:
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Stephen Rothwell authored
This patch changes the externally referenced names in mf.c to not use Study Caps and removes a couple of no longer used functions. Signed-off-by:
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Stephen Rothwell authored
Nothing more than removing trailing white space from mf.c. Signed-off-by:
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Stephen Rothwell authored
This patch just moves mf_proc.c into mf.c inanticipation of more cleanup to come. So mf_proc.c ceases to exist Signed-off-by:
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Kumar Gala authored
Remove initializations to zero in cpu_specs table at Tom Rini's suggestion. Signed-off-by:
Kumar Gala <kumar.gala@freescale.com> Signed-off-by:
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Kumar Gala authored
Remove __setup_cpu_8xx and its initialization in cpu_specs table since it hasn't every done anything. This is at Tom Rini's suggestion. Signed-off-by:
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Paul Mackerras authored
The linuxppc mailing lists that were at lists.linuxppc.org have moved to ozlabs.org. This patch updates the MAINTAINERS file to reflect that. Signed-off-by:
Paul Mackerras <paulus@samba.org> Signed-off-by:
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Mark A. Greer authored
No longer needed. Signed-off-by:
Mark Greer <mgreer@mvista.com> Signed-off-by:
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Kumar Gala authored
Adds the number of performance monitor counters each PowerPC processor has to the cpu table. Makes oprofile support a bit cleaner since we dont need a case statement on processor version to determine the number of counters. Signed-off-by:
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Kumar Gala authored
Fixes up the reporting of the e500 core revision. Additionally, it changes the reporting of CPU frequency to match what other PPC systems do. Signed-off-by:
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Kumar Gala authored
Here is patch that fixes a compile warning with rheap Signed-off-by:
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Kumar Gala authored
This patch adds OCP, interrupt, and memory offset details for the security block on MPC8555/8541 to support drivers. Signed-off-by:
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Mark A. Greer authored
This patch adds a routine that sets up indirect pci config space access but doesn't ioremap the config space addr/data registers. Signed-off-by:
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Suparna Bhattacharya authored
The O_SYNC speedup patches missed the generic_file_xxx_nolock cases, which means that pages weren't actually getting sync'ed in those cases. This patch fixes that. Signed-off-by:
Suparna Bhattacharya <suparna@in.ibm.com> Signed-off-by:
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Jesse Barnes authored
profile_hook unconditionally takes a read lock on profile_lock if kernel profiling is enabled. The lock protects the profile_hook notifier chain from being written while it's being called. The routine profile_hook is called in a very hot path though: every timer tick on every CPU. As you can imagine, on a large system, this makes the cacheline containing profile_lock pretty hot. Since oprofile was the only user of the profile_hook, I removed the notifier chain altogether in favor of a simple function pointer with the help of John Levon. This removes all of the contention in the hot path since the variable is very seldom written and simplifies things a little to boot. Acked-by:
John Levon <levon@movementarian.org> Signed-off-by:
Jesse Barnes <jbarnes@sgi.com> Signed-off-by:
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Matthew Wilcox authored
On PA-RISC, we have a unified syscall table for 32 and 64 bit that uses macros to generate the appropriate syscall names (native vs compat). For this to work, we need consistent compat syscall names. Unfortunately, some recent additions drop the 'sys_'. Signed-off-by:
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- 10 Nov, 2004 2 commits
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Linus Torvalds authored
Silly #endif placement problem.
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Arnaldo Carvalho de Melo authored
"platform_rename_gsi" does not exist unless CONFIG_ACPI_BOOT is defined.
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