forked frompostgres/postgres
- Notifications
You must be signed in to change notification settings - Fork0
Add error codes to PANIC/FATAL error reports.#2
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to ourterms of service andprivacy statement. We’ll occasionally send you account related emails.
Already on GitHub?Sign in to your account
Open
kk-src wants to merge2 commits intomasterChoose a base branch
base:master
Could not load branches
Branch not found:{{ refName }}
Loading
Could not load tags
Nothing to show
Loading
Are you sure you want to change the base?
Some commits from the old base branch may be removed from the timeline, and old review comments may become outdated.
Uh oh!
There was an error while loading.Please reload this page.
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.Learn more about bidirectional Unicode characters
kk-src pushed a commit that referenced this pull requestJun 27, 2024
1. TruncateMultiXact() performs the SLRU truncations in a criticalsection. Deleting the SLRU segments calls ForwardSyncRequest(), whichwill try to compact the request queue if it's full(CompactCheckpointerRequestQueue()). That in turn allocates memory,which is not allowed in a critical section. Backtrace: TRAP: failed Assert("CritSectionCount == 0 || (context)->allowInCritSection"), File: "../src/backend/utils/mmgr/mcxt.c", Line: 1353, PID: 920981 postgres: autovacuum worker template0(ExceptionalCondition+0x6e)[0x560a501e866e] postgres: autovacuum worker template0(+0x5dce3d)[0x560a50217e3d] postgres: autovacuum worker template0(ForwardSyncRequest+0x8e)[0x560a4ffec95e] postgres: autovacuum worker template0(RegisterSyncRequest+0x2b)[0x560a50091eeb] postgres: autovacuum worker template0(+0x187b0a)[0x560a4fdc2b0a] postgres: autovacuum worker template0(SlruDeleteSegment+0x101)[0x560a4fdc2ab1] postgres: autovacuum worker template0(TruncateMultiXact+0x2fb)[0x560a4fdbde1b] postgres: autovacuum worker template0(vac_update_datfrozenxid+0x4b3)[0x560a4febd2f3] postgres: autovacuum worker template0(+0x3adf66)[0x560a4ffe8f66] postgres: autovacuum worker template0(AutoVacWorkerMain+0x3ed)[0x560a4ffe7c2d] postgres: autovacuum worker template0(+0x3b1ead)[0x560a4ffecead] postgres: autovacuum worker template0(+0x3b620e)[0x560a4fff120e] postgres: autovacuum worker template0(+0x3b3fbb)[0x560a4ffeefbb] postgres: autovacuum worker template0(+0x2f724e)[0x560a4ff3224e] /lib/x86_64-linux-gnu/libc.so.6(+0x27c8a)[0x7f62cc642c8a] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x85)[0x7f62cc642d45] postgres: autovacuum worker template0(_start+0x21)[0x560a4fd16f31]To fix, bail out in CompactCheckpointerRequestQueue() without doinganything, if it's called in a critical section. That covers the abovecall path, as well as any other similar cases whereRegisterSyncRequest might be called in a critical section.2. After fixing that, another problem became apparent: Autovacuumprocess doing that truncation can deadlock with the checkpointerprocess. TruncateMultiXact() sets "MyProc->delayChkptFlags |=DELAY_CHKPT_START". If the sync request queue is full and cannot becompacted, the process will repeatedly sleep and retry, until there isroom in the queue. However, if the checkpointer is trying to start acheckpoint at the same time, and is waiting for the DELAY_CHKPT_STARTprocesses to finish, the queue will never shrink.More concretely, the autovacuum process is stuck here: #0 0x00007fc934926dc3 in epoll_wait () from /lib/x86_64-linux-gnu/libc.so.6#1 0x000056220b24348b in WaitEventSetWaitBlock (set=0x56220c2e4b50, occurred_events=0x7ffe7856d040, nevents=1, cur_timeout=<optimized out>) at ../src/backend/storage/ipc/latch.c:1570#2 WaitEventSetWait (set=0x56220c2e4b50, timeout=timeout@entry=10, occurred_events=<optimized out>, occurred_events@entry=0x7ffe7856d040, nevents=nevents@entry=1, wait_event_info=wait_event_info@entry=150994949) at ../src/backend/storage/ipc/latch.c:1516#3 0x000056220b243224 in WaitLatch (latch=<optimized out>, latch@entry=0x0, wakeEvents=wakeEvents@entry=40, timeout=timeout@entry=10, wait_event_info=wait_event_info@entry=150994949) at ../src/backend/storage/ipc/latch.c:538#4 0x000056220b26cf46 in RegisterSyncRequest (ftag=ftag@entry=0x7ffe7856d0a0, type=type@entry=SYNC_FORGET_REQUEST, retryOnError=true) at ../src/backend/storage/sync/sync.c:614#5 0x000056220af9db0a in SlruInternalDeleteSegment (ctl=ctl@entry=0x56220b7beb60 <MultiXactMemberCtlData>, segno=segno@entry=11350) at ../src/backend/access/transam/slru.c:1495postgres#6 0x000056220af9dab1 in SlruDeleteSegment (ctl=ctl@entry=0x56220b7beb60 <MultiXactMemberCtlData>, segno=segno@entry=11350) at ../src/backend/access/transam/slru.c:1566postgres#7 0x000056220af98e1b in PerformMembersTruncation (oldestOffset=<optimized out>, newOldestOffset=<optimized out>) at ../src/backend/access/transam/multixact.c:3006postgres#8 TruncateMultiXact (newOldestMulti=newOldestMulti@entry=3221225472, newOldestMultiDB=newOldestMultiDB@entry=4) at ../src/backend/access/transam/multixact.c:3201postgres#9 0x000056220b098303 in vac_truncate_clog (frozenXID=749, minMulti=<optimized out>, lastSaneFrozenXid=749, lastSaneMinMulti=3221225472) at ../src/backend/commands/vacuum.c:1917postgres#10 vac_update_datfrozenxid () at ../src/backend/commands/vacuum.c:1760postgres#11 0x000056220b1c3f76 in do_autovacuum () at ../src/backend/postmaster/autovacuum.c:2550postgres#12 0x000056220b1c2c3d in AutoVacWorkerMain (startup_data=<optimized out>, startup_data_len=<optimized out>) at ../src/backend/postmaster/autovacuum.c:1569and the checkpointer is stuck here: #0 0x00007fc9348ebf93 in clock_nanosleep () from /lib/x86_64-linux-gnu/libc.so.6#1 0x00007fc9348fe353 in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6#2 0x000056220b40ecb4 in pg_usleep (microsec=microsec@entry=10000) at ../src/port/pgsleep.c:50#3 0x000056220afb43c3 in CreateCheckPoint (flags=flags@entry=108) at ../src/backend/access/transam/xlog.c:7098#4 0x000056220b1c6e86 in CheckpointerMain (startup_data=<optimized out>, startup_data_len=<optimized out>) at ../src/backend/postmaster/checkpointer.c:464To fix, add AbsorbSyncRequests() to the loops where the checkpointerwaits for DELAY_CHKPT_START or DELAY_CHKPT_COMPLETE operations tofinish.Backpatch to v14. Before that, SLRU deletion didn't callRegisterSyncRequest, which avoided this failure. I'm not sure if thereare other similar scenarios on older versions, but we haven't hadany such reports.Discussion:https://www.postgresql.org/message-id/ccc66933-31c1-4f6a-bf4b-45fef0d4f22e@iki.fikk-src pushed a commit that referenced this pull requestOct 17, 2024
1. TruncateMultiXact() performs the SLRU truncations in a criticalsection. Deleting the SLRU segments calls ForwardSyncRequest(), whichwill try to compact the request queue if it's full(CompactCheckpointerRequestQueue()). That in turn allocates memory,which is not allowed in a critical section. Backtrace: TRAP: failed Assert("CritSectionCount == 0 || (context)->allowInCritSection"), File: "../src/backend/utils/mmgr/mcxt.c", Line: 1353, PID: 920981 postgres: autovacuum worker template0(ExceptionalCondition+0x6e)[0x560a501e866e] postgres: autovacuum worker template0(+0x5dce3d)[0x560a50217e3d] postgres: autovacuum worker template0(ForwardSyncRequest+0x8e)[0x560a4ffec95e] postgres: autovacuum worker template0(RegisterSyncRequest+0x2b)[0x560a50091eeb] postgres: autovacuum worker template0(+0x187b0a)[0x560a4fdc2b0a] postgres: autovacuum worker template0(SlruDeleteSegment+0x101)[0x560a4fdc2ab1] postgres: autovacuum worker template0(TruncateMultiXact+0x2fb)[0x560a4fdbde1b] postgres: autovacuum worker template0(vac_update_datfrozenxid+0x4b3)[0x560a4febd2f3] postgres: autovacuum worker template0(+0x3adf66)[0x560a4ffe8f66] postgres: autovacuum worker template0(AutoVacWorkerMain+0x3ed)[0x560a4ffe7c2d] postgres: autovacuum worker template0(+0x3b1ead)[0x560a4ffecead] postgres: autovacuum worker template0(+0x3b620e)[0x560a4fff120e] postgres: autovacuum worker template0(+0x3b3fbb)[0x560a4ffeefbb] postgres: autovacuum worker template0(+0x2f724e)[0x560a4ff3224e] /lib/x86_64-linux-gnu/libc.so.6(+0x27c8a)[0x7f62cc642c8a] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x85)[0x7f62cc642d45] postgres: autovacuum worker template0(_start+0x21)[0x560a4fd16f31]To fix, bail out in CompactCheckpointerRequestQueue() without doinganything, if it's called in a critical section. That covers the abovecall path, as well as any other similar cases whereRegisterSyncRequest might be called in a critical section.2. After fixing that, another problem became apparent: Autovacuumprocess doing that truncation can deadlock with the checkpointerprocess. TruncateMultiXact() sets "MyProc->delayChkptFlags |=DELAY_CHKPT_START". If the sync request queue is full and cannot becompacted, the process will repeatedly sleep and retry, until there isroom in the queue. However, if the checkpointer is trying to start acheckpoint at the same time, and is waiting for the DELAY_CHKPT_STARTprocesses to finish, the queue will never shrink.More concretely, the autovacuum process is stuck here: #0 0x00007fc934926dc3 in epoll_wait () from /lib/x86_64-linux-gnu/libc.so.6#1 0x000056220b24348b in WaitEventSetWaitBlock (set=0x56220c2e4b50, occurred_events=0x7ffe7856d040, nevents=1, cur_timeout=<optimized out>) at ../src/backend/storage/ipc/latch.c:1570#2 WaitEventSetWait (set=0x56220c2e4b50, timeout=timeout@entry=10, occurred_events=<optimized out>, occurred_events@entry=0x7ffe7856d040, nevents=nevents@entry=1, wait_event_info=wait_event_info@entry=150994949) at ../src/backend/storage/ipc/latch.c:1516#3 0x000056220b243224 in WaitLatch (latch=<optimized out>, latch@entry=0x0, wakeEvents=wakeEvents@entry=40, timeout=timeout@entry=10, wait_event_info=wait_event_info@entry=150994949) at ../src/backend/storage/ipc/latch.c:538#4 0x000056220b26cf46 in RegisterSyncRequest (ftag=ftag@entry=0x7ffe7856d0a0, type=type@entry=SYNC_FORGET_REQUEST, retryOnError=true) at ../src/backend/storage/sync/sync.c:614#5 0x000056220af9db0a in SlruInternalDeleteSegment (ctl=ctl@entry=0x56220b7beb60 <MultiXactMemberCtlData>, segno=segno@entry=11350) at ../src/backend/access/transam/slru.c:1495postgres#6 0x000056220af9dab1 in SlruDeleteSegment (ctl=ctl@entry=0x56220b7beb60 <MultiXactMemberCtlData>, segno=segno@entry=11350) at ../src/backend/access/transam/slru.c:1566postgres#7 0x000056220af98e1b in PerformMembersTruncation (oldestOffset=<optimized out>, newOldestOffset=<optimized out>) at ../src/backend/access/transam/multixact.c:3006postgres#8 TruncateMultiXact (newOldestMulti=newOldestMulti@entry=3221225472, newOldestMultiDB=newOldestMultiDB@entry=4) at ../src/backend/access/transam/multixact.c:3201postgres#9 0x000056220b098303 in vac_truncate_clog (frozenXID=749, minMulti=<optimized out>, lastSaneFrozenXid=749, lastSaneMinMulti=3221225472) at ../src/backend/commands/vacuum.c:1917postgres#10 vac_update_datfrozenxid () at ../src/backend/commands/vacuum.c:1760postgres#11 0x000056220b1c3f76 in do_autovacuum () at ../src/backend/postmaster/autovacuum.c:2550postgres#12 0x000056220b1c2c3d in AutoVacWorkerMain (startup_data=<optimized out>, startup_data_len=<optimized out>) at ../src/backend/postmaster/autovacuum.c:1569and the checkpointer is stuck here: #0 0x00007fc9348ebf93 in clock_nanosleep () from /lib/x86_64-linux-gnu/libc.so.6#1 0x00007fc9348fe353 in nanosleep () from /lib/x86_64-linux-gnu/libc.so.6#2 0x000056220b40ecb4 in pg_usleep (microsec=microsec@entry=10000) at ../src/port/pgsleep.c:50#3 0x000056220afb43c3 in CreateCheckPoint (flags=flags@entry=108) at ../src/backend/access/transam/xlog.c:7098#4 0x000056220b1c6e86 in CheckpointerMain (startup_data=<optimized out>, startup_data_len=<optimized out>) at ../src/backend/postmaster/checkpointer.c:464To fix, add AbsorbSyncRequests() to the loops where the checkpointerwaits for DELAY_CHKPT_START or DELAY_CHKPT_COMPLETE operations tofinish.Backpatch to v14. Before that, SLRU deletion didn't callRegisterSyncRequest, which avoided this failure. I'm not sure if thereare other similar scenarios on older versions, but we haven't hadany such reports.Discussion:https://www.postgresql.org/message-id/ccc66933-31c1-4f6a-bf4b-45fef0d4f22e@iki.fiSign up for freeto join this conversation on GitHub. Already have an account?Sign in to comment
Labels
None yet
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
No description provided.